Volume 7, No. 4, pp. 349-472, 47 figures in text, 4 tables

Published April 21, 1954

UNIVERSITY OF KANSAS LAWRENCE, KANSAS

PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1954

25-1128

North American Jumping Mice (Genus Zapus)

by

Philip H. Krutzsch

CONTENTS

PAGE

Introduction 351

Materials, Methods, and Acknowledgments 352

Paleontology of the Genus 355

Relationships, Distribution, and Speciation 356

Annotated List of Specific and Subspecific Names 369

Characters of Taxonomic Worth 371

Nongeographic Variation 376

Check-List of the Species and Subspecies of the Genus Zapus 382

Genus Zapus 382

Artificial Key to the Species of the Genus Zapus 384

Systematic Accounts of Species and Subspecies 385

_Zapus trinotatus_ 385

_Zapus princeps_ 394

_Zapus hudsonius_ 420

Tables of Measurements 455

Literature Cited 466

INTRODUCTION

The jumping mice (Genus _Zapus_) are widely distributed over northern North America, occurring as far north as the Arctic Circle and as far south as Georgia, Missouri, Oklahoma, New Mexico, Arizona, and central California. In some years these small rodents are locally common in moist places that are either grassy or weedy; the jumping mice are notable for the much enlarged hind legs and the exceptionally long tail.

Members of the Genus as a whole have received no serious comprehensive taxonomic attention in the 54 years since Preble's (1899) revisionary work. In this time 15 new names have been proposed, mostly for subspecies, and only a few attempts have been made at grouping related named kinds.

In the present account it is aimed to record what is known concerning geographic distribution, taxonomically significant characters, and interrelationships of the known kinds as well as to provide means for recognizing the species and subspecies in the genus. In addition, attention is given to the probable center of origin of the subfamily Zapodinae and to the relationships and taxonomic positions of the genera _Zapus_, _Napaeozapus_, and _Eozapus_.

MATERIALS, METHODS, AND ACKNOWLEDGMENTS

The present report is based on a study of approximately 3,600 specimens that were assembled at the Museum of Natural History of the University of Kansas or that were examined at other institutions. Most of these specimens are stuffed skins with skulls separate. Skulls without skins, skins without skulls, entire skeletons, and separately preserved bacula are included as a part of the total. Almost every specimen is accompanied by an attached label, which bears place and date of capture, name of collector, external measurements, and sex.

Specimens used in the study of geographic variation were arranged by season of capture and according to geographic location; then they were segregated as to sex, and, under each sex, by age. Next, individual variation was measured in comparable samples of like age, sex, season, and geographic origin. Finally, comparable materials were arranged geographically in order to determine variations of systematic significance.

The only external measurements used were total length, length of tail, and length of hind foot; these measurements were recorded by the collectors on the labels attached to the skins. Height of the ear was not used since it was not recorded by many of the collectors.

In order to determine which cranial structures showed the least individual variation but at the same time showed substantial geographic variation, a statistical analysis was made of the 30 measurements, of cranial structures, heretofore used in taxonomic work on _Zapus_. The following measurements of the skull showed the least individual variation but showed some geographic variation and therefore, were used in this study. See figs. 1-3 which show points between which measurements were taken:

_Occipitonasal length._--From anteriormost projection of nasal bones to posteriormost projection of supraoccipital bone. _a_ to _a´_

_Condylobasal length._--Least distance from a line connecting posteriormost parts of exoccipital condyles to a line connecting anteriormost projections of premaxillary bones. _b_ to _n_

_Palatal length._--From anterior border of upper incisors to anteriormost point of postpalatal notch. _b_ to _b´_

_Incisive foramina, length._--From anteriormost point to posteriormost point of incisive foramina. _c_ to _c´_

_Incisive foramina, breadth._--Greatest distance across incisive foramina perpendicular to long axis of skull. _f_ to _f´_

_Zygomatic length._--From anteriormost point of zygomatic process of maxillary to posteriormost point of zygomatic process of squamosal. _d_ to _d´_

_Zygomatic breadth._--Greatest distance across zygomatic arches of cranium at right angles to long axis of skull. _j_ to _j´_

_Breadth of inferior ramus of zygomatic process of maxillary._--Greatest distance across inferior ramus of zygomatic process of maxillary taken parallel to long axis of skull. _d_ to _e_

_Palatal breadth at M3._--Greatest distance from inside margin of alveolus of right M3 to its opposite. _g_ to _g´_

_Palatal breadth at P4._--Same as above except taken at P4. _g_ to _g´_

_Mastoid breadth._--Greatest distance across mastoid bones perpendicular to long axis of skull. _h_ to _h´_

_Breadth of braincase._--Greatest distance across braincase taken perpendicular to long axis of skull. _i_ to _i´_

_Interorbital breadth._--Least distance across top of skull between orbits. _k_ to _k´_

_Length of maxillary tooth-row._--From anterior border of P4 to posterior border of M3. _l_ to _l´_

_Breadth of base zygomatic process of squamosal._--Greatest distance across base of zygomatic process of squamosal taken parallel to long axis of skull. _m_ to _m´_

The baculum has a characteristic size and shape according to the species, and the following significant measurements of the structure were taken:

_Greatest length._--From posteriormost border of base to anteriormost point on tip.

_Greatest breadth at base._--Greatest distance across base taken parallel to long axis of bone.

_Greatest breadth at tip._--Greatest distance across tip taken parallel to long axis of bone.

In the descriptions of color the capitalized color terms refer to those in Ridgway (1912). Any color term that does not have the initial letter capitalized does not refer to any one standard.

In the description of the subspecies the two sexes are treated as one because no significant secondary sexual variation was found. Only fully adult specimens of age groups 3 to 5, as defined on pages 377 and 388, have been considered.

Unless otherwise indicated, specimens are in the University of Kansas Museum of Natural History. Those in other collections are identified by the following abbreviations:

AMNH. American Museum of Natural History. CAS. California Academy of Science. CM. Carnegie Museum. Chic. AS. Chicago Academy of Science. Clev. MNH. Cleveland Museum of Natural History. LMH. Collection of Lawrence M. Huey. JKJ. Collection of J. Knox Jones, Jr. CMNH. Colorado Museum of Natural History. FM. Chicago Museum of Natural History. HM. Hastings Museum, Hastings, Nebraska. ISC. Iowa State College. MCZ. Museum of Comparative Zoology. MO. University of Missouri Museum of Zoology. MVZ. Museum of Vertebrate Zoology, Berkeley, Calif. NMC. National Museum of Canada. NGFP. Nebraska Game, Forestation, and Parks Commission. NCS. North Carolina State College. OHIO. Ohio Wildlife Research Unit, Ohio State University. OKLA. Oklahoma Agricultural and Mechanical College. PM. Provincial Museum of British Columbia. ROM. Royal Ontario Museum of Zoology. SDM. San Diego Natural History Museum. SITC. Southern Illinois Teachers College. USBS. United States Biological Surveys Collection. USNM. United States National Museum. UCM. University of Colorado Museum. UIM. University of Illinois Museum of Natural History. UM. University of Michigan Museum of Zoology. UU. University of Utah Museum of Zoology.

The species are arranged from least to most progressive, and the subspecies are arranged alphabetically.

The synonymy for each subspecies includes first a citation to the earliest available name then one citation to each name combination that has been applied to the subspecies and, finally, any other especially important references.

Marginal records of occurrence for each subspecies are shown on the maps by means of hollow circles and these localities are listed in clockwise order beginning with the northernmost locality. If more than one of these localities lies on the line of latitude that is northernmost for a given subspecies the western-most of these is recorded first. Marginal localities have been cited in a separate paragraph at the end of the section on specimens examined in the account of a subspecies. Localities that are not marginal are shown on the maps by solid black circles. Localities that could not be represented on the distribution map because of undue crowding or overlapping of symbols are italicized in the lists of specimens examined and in the lists of marginal records.

The localities of capture of specimens examined are recorded alphabetically by state or province, and then by county in each state or province. Within a county the specimens are recorded geographically from north to south. The word "County" is written out in full when the name of the county is written on the label of each specimen listed for that county, but the abbreviation "Co." is used when one specimen or more here assigned to a given county lacks the name of the county on the label.

The following account has been made possible only by the kindness and cooperation of those persons in charge of the collections listed above. For the privilege of using the specimens in their care I am deeply grateful, as I am also to Prof. A. Byron Leonard for assistance with figures 35-37, to Dr. Rufus Thompson for figures 16-21, and to Mr. Victor Hogg who made all of the other illustrations. My wife, Dorothy Krutzsch, helped untiringly in assembling data, in typing the manuscript, and gave me continued encouragement. Finally, I am grateful to Professor E. Raymond Hall for guidance in the study and critical assistance in the preparation of the manuscript and to Professors Rollin H. Baker, Robert W. Wilson, and Robert E. Beer for valued suggestions.

PALEONTOLOGY OF THE GENUS

The fossil record of the genus _Zapus_ is scanty. All of the known fossils of it are lower jaws of Pleistocene Age. The Recent species _Z. hudsonius_ was recorded by Cope (1871:86) in the Port Kennedy Cave fauna (pre-Wisconsinian) of Pennsylvania. Gidley and Gazin (1938:67) reported a single mandibular ramus bearing m1-m3 recovered from the Cumberland Cave (pre-Wisconsinian) of Maryland. The teeth are not typical of modern _Zapus_ in that m1 and m2 are shorter crowned and m1 has a longer anterior lobe. Gidley and Gazin, nevertheless, considered their material insufficient for establishing a new species.

Two extinct species have been described: _Zapus burti_ Hibbard (1941:215) from the Crooked Creek formation (= Meade formation of the State Geological Survey of Kansas) mid-Pleistocene of Kansas and _Zapus rinkeri_ Hibbard (1951:351) from the Rexroad formation (= Blanco formation of the State Geological Survey of Kansas) of Blancan Age of Kansas. Both species resemble _Zapus hudsonius_, but differ from it in broader crowned more brachydont cheek-teeth. _Z. rinkeri_ differs from _Z. burti_ and _Z. hudsonius_ by a more robust ramus, broader molars, and three instead of two internal re-entrant valleys posterior to the anterior loop on m1. The three species _Z. rinkeri_, _Z. burti_, and _Z. hudsonius_ are in a structurally, as well as a geologically, progressive series. The trend in dentition is from broad, brachydont cheek-teeth to narrow, semi-hypsodont cheek-teeth.

RELATIONSHIPS, DISTRIBUTION, AND SPECIATION

Relationships in the Subfamily Zapodinae

The subfamily Zapodinae is known from Pliocene and Pleistocene deposits of North America and now occurs over much of northern North America and in Szechuan and Kansu, China. The living species occur among grasses and low herbs in damp or marshy places both in forested areas and in plains areas.

The early Pliocene _Macrognathomys nanus_ Hall (1930:305), originally described as a Cricetid, is actually a Zapodid as shown by the structure of the mandibular ramus, shape of the incisors, and occlusal pattern of the cheek-teeth.

If _Macrognathomys_ can be considered a member of the subfamily Zapodinae (possibly it is a sicistine) then it represents the oldest known member of this subfamily. Judging from the published illustrations, _Macrognathomys_ seems to be structurally ancestral to the Mid Pliocene _Pliozapus solus_ Wilson; the labial re-entrant folds are wider and shorter and on m2 and m3 fewer. The difference in stage of wear of the teeth in _Macrognathomys_ and _Pliozapus_ is a handicap in comparing the two genera but they are distinct. Wilson (1936:32) points out that _Pliozapus_ clearly falls in the Zapodinae and stands in an ancestral position with respect to the structurally progressive series _Eozapus_, _Zapus_, and _Napaeozapus_. Nevertheless, _Pliozapus_ cannot be considered as directly ancestral to _Eozapus_ because of the progressive features in the dentition of _Pliozapus_. Wilson (1937:52) remarked that if _Pliozapus_ is ancestral to _Zapus_ and _Napaeozapus_, considerable evolution must have taken place in the height of crown and in the development of the complexity of the tooth pattern. In contrast to Wilson's opinion, Stehlin and Schaub (1951:313) placed _Pliozapus_ and _Eozapus_ in the subfamily Sicistinae because certain elements in the occlusal pattern of the cheek-teeth are similar. I disagree with those authors and hold with Wilson; I consider _Pliozapus_ and _Eozapus_ in the subfamily Zapodinae. In dental pattern _Pliozapus_, as Wilson (1936:32) pointed out, resembles the Recent Eurasiatic sicistid, _Sicista_ more than do _Zapus_ or _Napaeozapus_. Nevertheless, from _Sicista_ Wilson distinguishes _Pliozapus_ and relates it to the subfamily Zapodinae by: "more oblique direction of protoconid-hypoconid ridge, anterior termination of this ridge at buccal portion of protoconid rather than between protoconid and metaconid as in _Sicista_; cusps more compressed into lophs; cheek-teeth somewhat broader; greater development of metastylid; greater development of hypoconulid ridge, ... absence of anteroconid...."

_Eozapus_ is more closely related to _Pliozapus_ than to either _Zapus_ or _Napaeozapus_ (Wilson, 1936:32) but all four genera are in the subfamily Zapodinae. Stehlin and Schaub (op. cit.:158 and 311) relate _Eozapus_ to the subfamily Sicistinae on the basis of similarity in the occlusal pattern of the cheek-teeth of _Eozapus_ and various sicistines. Stehlin and Schaub do not consider other structures such as the elongate hind limbs, the shape of malleus and incus, and the shape of the baculum, in which there is close resemblance to the Zapodinae. It is these structural similarities as well as those, pointed out by Wilson (_loc. cit._), in dentition that leads me to place _Eozapus_ in the subfamily Zapodinae. The early Pleistocene _Zapus rinkeri_ Hibbard shows that the _Zapus_ stage of development had already been achieved perhaps as early as the late Pliocene. Hibbard (1951:352) thought that _Zapus rinkeri_ was not structurally intermediate between _Pliozapus_ and any Recent species of _Zapus_; although the teeth of _Z. rinkeri_ have the broader, shallower, re-entrant folds of _Pliozapus_, these teeth are higher crowned and have an occlusal pattern resembling that of the Recent species of _Zapus_. The middle Pleistocene species, _Zapus burti_ Hibbard, progressed essentially to the structural level of the Recent _Zapus hudsonius_, but the molars were more brachydont, broader crowned, and their enamel folds less crowded. Pleistocene material of pre-Wisconsin age obtained from cave deposits in Pennsylvania and Maryland is most nearly like _Zapus hudsonius_. One such cave deposit in Maryland contained an example of the Recent genus _Napaeozapus_, indicating that its history dates from at least middle Pleistocene time.

The Asiatic Recent Genus, _Eozapus_, has not progressed much beyond the Pliocene stage in zapidine evolution if _Pliozapus_ be taken as a standard; the North American Recent Genus _Zapus_ essentially achieved its present form by early Pleistocene times, and the Recent Genus _Napaeozapus_ achieved its more progressive structure by middle Pleistocene times.

Perhaps _Pliozapus_ and _Eozapus_ represent one phyletic line and _Zapus_ and _Napaeozapus_ a second line, both of which lines evolved from a pre-zapidine stock in the Miocene. As mentioned earlier, Wilson (1936) thinks that _Pliozapus_ is not directly ancestral to _Eozapus_. Possibly these two genera diverged at an early date; nevertheless, they are closely related primitive forms.

_Zapus_ and _Napaeozapus_ closely resemble each other and both are structurally advanced; _Napaeozapus_ seems to have differentiated at a more rapid rate.

According to Simpson (1947), the occurrence of the same group of mammals on two different land masses is to be taken as prima facie evidence that migration has occurred. Keeping in mind then the present geographic distribution, unspecialized condition of the dentition of _Eozapus_, and its resemblance to the extinct _Pliozapus_ known from North America but not from Asia, it may be that _Eozapus_ descended from primitive stock of a North American jumping mouse that was forced to the periphery (across the Asiatic North American land bridge) by the more specialized zapidine stock.

Subsequently or perhaps during the migration of the pre-_Eozapus_ stock the zapidine stock may have dispersed transcontinentally, occupying most of northern North America. The unprogressive _Macrognathomys_ and _Pliozapus_ line which remained in North America may have become extinct. Any such period of dispersal and climatic equilibrium ended when glaciers came to cover most of the northern part of the continent and the mammals living there were forced southward by the ice or remained in ice-free refugia within the glaciated area. Later, with melting and retreat of the ice, the jumping mice could have again spread enough to occupy the northern part of the continent. Such glaciation isolated segments of the population and aided their evolution into distinct species.

If it be assumed, as Matthew (1915) did and as Hooper (1952:200) later on the generic level did, that the region of origin and center of dispersal for a given group of animals is characterized by the presence of the most progressive forms, then southeastern Canada and the northeastern United States make up the area of origin and center of dispersal in relatively late time of the subfamily Zapodinae. This area is inhabited by _Zapus hudsonius_ and _Napaeozapus_, the most progressive members of the subfamily.

As I visualize it, the evolution of the Zapodinae occurred in two stages: the first stage involved the movement of the primitive pre-_Eozapus_ stock to Asia and the second stage involved the dispersal, isolation, and specialization in North America of the more progressive basic zapidine stock into the present genera _Zapus_ and _Napaeozapus_.

Status of the genera _Eozapus_, _Zapus_, and _Napaeozapus_

The genus _Zapus_ is one of three living genera in the subfamily Zapodinae. These genera _Zapus_ and _Napaeozapus_ from North America and _Eozapus_ from China have been variously considered as subgenera of the genus _Zapus_ (Preble, 1899) or as three separate genera (Ellerman, 1940).

The remarkable similarity of the body form, post-cranial skeleton, mandibular rami, and general structure of the cranium of _Zapus_, _Napaeozapus_, and _Eozapus_ indicate their relationship (see figs. 4-15); however, dissimilarity between the groups in the dentition (tooth number and occlusal pattern), bacula, and ear ossicles provides basis for considering them distinct genera. As pointed out earlier, _Zapus_ and _Napaeozapus_ appear to be more closely related and progressive and the Asiatic _Eozapus_ somewhat removed and less progressive.

_Teeth._--According to the complexity in dental pattern and in number and size of the cheek-teeth, these genera can be arranged in a structurally progressive series with _Eozapus_ showing the least complexity and _Napaeozapus_ the most (see figs. 16-21). There are three distinct molar patterns; one is simple (_Eozapus_) and the others (_Zapus_ and _Napaeozapus_) are more complex. The complexity is greatest in _Napaeozapus_, which is characterized by numerous additional flexures in the enamel and dentine. The simplicity of the molars of _Eozapus_ is evident in the tuberculate rather than flat-crowned occlusal surface; the wide, simple, re-entrant bays; the small (or sometimes absent) anteroconid; and the essentially quadritubercular nature of the teeth. The molars of _Zapus_ and _Napaeozapus_ are flat crowned; however, _Zapus_ has wider and fewer re-entrant bays, a smaller anteroconid, and less complexity in the occlusal pattern. The characteristics of the molar teeth would tend to indicate a close relationship between _Zapus_ and _Napaeozapus_ and to place _Eozapus_ as primitive.

The absence of P4 in _Napaeozapus_ would lead one to suspect that this genus has evolved at a more rapid rate than the historically older _Zapus_ and _Eozapus_ which still retain this structure. The small size of P4, even in the primitive _Eozapus_, indicates that it has long been of little use to the mouse. An even greater reduction of P4 in the more complex dentition of _Zapus_ argues for complete loss of this tooth as the next step in specialization, such as is seen in the more progressive _Napaeozapus_. The following parallel columns show selected differences between the occlusal patterns of the cheek-teeth of the three genera:

BACULUM.--The baculum (os penis) of _Eozapus_ is known to me only from Vinogradov's (1925) figures of the dorsal and lateral aspects. The proximal end (base) is laterally expanded, and the shaft tapers gradually toward the distal end where it expands abruptly into the spade-shaped tip. In lateral aspect the bone is relatively thick; it is curved downward slightly from the proximal end to the base of the tip where it curves upward to a rounded point.

The baculum of _Zapus_ differs from that of _Eozapus_ as follows: base less expanded horizontally; shaft slenderer; distal end less spade-shaped except in _Z. trinotatus_. The tip is less expanded in _Z. princeps_ and is still less so in _Z. hudsonius_. In _Napaeozapus_ the tip is lanceolate, the base is narrow, and in lateral view the shaft is slender and curved (see figs. 22-31).

-----------------------+-----------------------+----------------------- _Eozapus_ | _Zapus_ | _Napaeozapus_ -----------------------+-----------------------+----------------------- P4--Small | Smaller | Absent | | M1--Four wide labial | Four moderately | Three narrow labial re-entrant folds | narrow labial | re-entrant folds of equal length; | re-entrant folds | of unequal length, paracone and | of unequal length; | 1st long, 2d and 3d metacone largest | 1st and 3d longer | shorter; paracone cusps; anterior | than 2d, 4th | and metacone larger cingulum large. | shortest; paracone | than in _Zapus_ and | smaller than in | _Eozapus_; anterior | _Eozapus_; metacone | cingulum absent. | largest cusp; | | anterior cingulum | | small. | | | | | M2--Four wide labial | Four moderately | Narrow labial re-entrant folds; | narrow labial | re-entrant folds, 2d short, others | re-entrant folds | variable in number, of equal length | of unequal length, | often as many as 6; but longer than | 1st and 3d long, | anterior and 2d; anterior and | 2d and 4th short; | posterior cingula posterior cingula | anterior and | small; occlusal large; occlusal | posterior cingula | pattern complex. pattern simple. | moderately large; | | occlusal pattern | | moderately complex. | | | | | M3--Three wide labial | Two moderately | Three narrow labial re-entrant folds | narrow labial | re-entrant folds of unequal length, | re-entrant folds | of unequal length, 1st short, 2d and | of equal length; | 1st long, 2d and 3d long; anterior | anterior and | 3d short; anterior and posterior | posterior cingula | and posterior cingula low, | moderately large; | cingula large; small; occlusal | occlusal pattern | occlusal pattern pattern simple. | moderately complex. | complex. | | | | m1--Anterior oblique | No anterior | No anterior re-entrant fold | re-entrant fold; 4 | re-entrant fold; separating equal | moderately narrow | narrow lingual sized protoconid | lingual re-entrant | re-entrant folds and metaconid | folds of equal | variable in cusps; 3 wide | length, 1st joining | number, often as lingual re-entrant | 1st labial | many as 4; folds of equal | re-entrant fold, | anteroconid well length; | 4th joining 2d | developed, encloses anteroconid absent;| labial re-entrant | 1 or 2 small lakes; occlusal pattern | fold; anteroconid | occlusal pattern simple; mesoconid | well developed, | complex; mesoconid present. | encloses | absent. | small lake; occlusal | | pattern moderately | | complex; | | mesoconid absent. | | | | | m2--Four wide lingual | Four moderately | Narrow lingual re-entrant folds | narrow lingual | re-entrant folds, of unequal length, | re-entrant folds, | variable in number, 1st short, other | 1st and 2d long, 3d | may be as many as 5; 3 equal and long; | and 4th short, 1st | anteroconid large, anteroconid | joins 1st labial | encloses moderately large; | re-entrant fold | complex folds from occlusal pattern | and 4th joins 2d | 1st labial re-entrant simple. | labial re-entrant | fold; occlusal | fold; anteroconid | pattern complex. | large; occlusal | | pattern moderately | | complex. | | | | | m3--Three wide lingual | Three moderately | Narrow lingual re-entrant folds | narrow lingual | re-entrant of near equal | re-entrant folds | folds variable in length; antero- | of unequal length, | number, as many as 3; conid absent; | 1st and 2d long, 3d | anteroconid present; occlusal pattern | short; anteroconid | occlusal pattern simple; 1 labial | absent; occlusal | complex; 2 labial re-entrant fold. | pattern moderately | re-entrant folds. | complex; 1 labial | | re-entrant fold. | -----------------------+-----------------------+------------------------

EAR OSSICLES.--The auditory ossicles are of three types which differ only slightly. These ossicles possibly are more conservative than some other structures because the ossicles are not so much affected by the molding influence of the environment.

Instances of variation in the auditory region in mammals in general are small, even at the family level; therefore, these differences in the subfamily Zapodinae are offered as additional support for recognizing _Eozapus_, _Zapus_, and _Napaeozapus_ as distinct genera. The distinctive features are chiefly in the malleus and incus; the stapes, however, differs slightly and, therefore, it too is described (see figs. 32-34).

In _Eozapus_ the head of the malleus is narrow, oblong, and rounded dorsally and attaches to the body by a long, slender, abruptly recurved neck. The body is weakly pointed ventrally and rounded dorsally. A beaklike manubrium malleus composed of anterior projecting external and internal spines extends from the body to the tympanum. The incus has a dorsally rounded body with an anterior downward snoutlike projection with which the malleus articulates. The short limb of the incus is broad basally and narrows somewhat distally. The long limb is narrow and its articulating lenticular process is a flat circular structure. The limbs of the stapes are wide-spread and heavy. The neck is short and wide with a large circular articulating surface.

In _Zapus_ the head of the malleus is angular with an anterior projecting point and is flattened in dorsal aspect. The neck is slender, elongate, and gently curved away from the long limb of the incus. The body is pointed dorsally and rounded ventrally, the reverse of the condition in _Eozapus_. There is a beaklike manubrium malleus composed of internal and external anteriorly projecting spines extending from the body to the tympanum as in _Eozapus_. The incus has a rounded body with a long angular limb articulating via a small lenticular process with the stapes. The short limb is narrow but does not taper distally as in _Eozapus_. The limbs of the stapes are relatively narrow, weak, and gently curved. The neck is longer and more slender than that of _Eozapus_.

In _Napaeozapus_ the head and neck of the malleus resemble those of _Zapus_ but are less robust. The body is more rounded dorsally, having the curved dorsal surface directed anteriorly rather than posteriorly (as in _Zapus_) and the lateral surface is nearly flat instead of curved as in the other genera. The manubrium resembles that of _Eozapus_ and _Zapus_. The body of the incus is flattened dorsally but otherwise rounded. The long limb of the incus is angular and longer than that of _Zapus_. The short limb of the incus is broad at the base and tapers distally. The limbs of the stapes are narrow, weak, and abruptly curved. The neck is more slender and elongate than in _Zapus_.

In summary: Only the head and body of the malleus and the short and long limbs and body of the incus are sufficiently consistent within a given group to be of taxonomic importance. The similarity in the morphology of these ossicles indicates a close relationship between all three genera. _Zapus_ and _Napaeozapus_ resemble one another more than either resembles _Eozapus_. The differences recorded are constant between the described groups and, therefore, are considered to be of taxonomic significance. The differences give basis for dividing the subfamily Zapodinae into the three genera _Eozapus_, _Zapus_, and _Napaeozapus_.

Distribution of and Speciation in the Genus _Zapus_

Many of the described kinds of the genus _Zapus_ were initially named as distinct species (see Preble, 1899). Subsequently (see Hall, 1931), some of the nominal species were reduced to the rank of subspecies. Only three species in the genus _Zapus_ are recognized in the following account. The concept of species adopted here is, in Mayr's (1942:120) words, this: "Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups." The three species are _Z. trinotatus_, _Z. princeps_, and _Z. hudsonius_. No hybridization is known where two occur together or where their ranges are adjacent. Each of these species has several geographically contiguous subspecies.

The three species of _Zapus_ are closely related but are not equally progressive. If eastern North America is considered to be the region of origin and center of dispersal of _Zapus_ (see pp. 368-369) the geographically distant species would be expected to be the least progressive, and such seems to be the case. _Zapus trinotatus_ is geographically farthest removed and structurally least progressive. _Zapus hudsonius_ occurs at the center of dispersal and is the most progressive structurally whereas _Z. princeps_ is geographically and structurally intermediate. Structural progressiveness is postulated for the species that has the simplest (in this instance specialized) baculum and smallest fourth upper premolar. The phyletic branches of the genus _Zapus_ possibly developed from geographic segments of a population radiating from the centrally located progressive group. On continental areas where a species with a wide and continuous range gives rise to several daughter species, geographic isolation is thought to be important in bringing about the formation of species. The unspecialized populations conceivably occupied an area west of the present Rocky Mountains and south of latitude 50°. From later Miocene times on, climatic and geological differentiation occurred in this area, and with the growth of geological barriers and differentiation of habitat these unspecialized populations may have been separated into two ecological groups, one inhabiting the more arid area between the present Rocky Mountains and the present Cascade Range and Sierra Nevada and the other group inhabiting the Pacific coastal region. Isolation of each of these groups probably was not complete. How far differentiation might have proceeded with incomplete isolation can only be guessed, but at least incipient differences probably were present and possibly the animals approached in character those found in these areas today in that the ecology of the region was much the same as now.

In the region between the Rocky Mountains and the present Cascade Range and the Sierra Nevada, the flora (in late Pliocene) became semidesert, which presumably made most of this region uninhabitable for jumping mice. The aridity probably induced local concentration into boreal montane islands, thus possibly displacing the populations of the two species that were in contact.

In Pleistocene times continental glaciation must have interrupted the contacts between the coastal, intermontane (the area between the present Rocky Mountains and the present Cascade Range and the Sierra Nevada), and northern and eastern groups of _Zapus_ or mammals of any genus that occurred over all of this vast region. The advance of the ice southward would have increased opportunity for evolution by interposing barriers that isolated some populations. The populations possibly were re-established in interglacial periods and then were isolated again by another descent of glacial ice.

If a population occupied the unglaciated coastal region of Oregon and Washington it may have been separated from other populations to the north and east by an ice cap which covered most of the Cascade Range. The population occupying the intermountain region probably was isolated from the population to the north and west. The formation of glaciers presumably reduced the size of areas available to the populations occupying eastern North America, Alaska, and Canada with the result that they persisted only in areas south of the ice or in ice-free refugia (central and western Alaska) within the glaciated area. According to Axelrod (1948), the flora in the eastern United States during the Pleistocene furnished most of the stock for the revegetation of southern and subarctic Canada east of the Rocky Mountains. Eastern populations of _Z. hudsonius_ (or its progenitors) probably followed the spread of this vegetation and, thus, extended their range into Canada where they crossbred with populations advancing south and east from the refugia in Alaska. Western montane floras, which extended north along the Rocky Mountains and the Cascade and Coast ranges, probably paved the path for a northward migration of populations of the intermountain _Z. princeps_ (or its progenitors). Populations of _Z. princeps_ moved eastward from the present Rocky Mountains, inhabiting the high plains of southern Canada and the north-central United States. In general, _Zapus hudsonius_ occupies the region to the north and to the east of that inhabited by _Zapus princeps_; however, the ranges of the two meet and overlap in central and northern British Columbia and in the high plains area of southern Alberta, Saskatchewan, eastern Manitoba, eastern Montana, North Dakota, and northern South Dakota. In these places of overlap, owing to range expansion following the retreat of the ice, there is no sign of interbreeding, indicating that the populations have attained specific rank.

Populations of both _Z. hudsonius_ and _Z. princeps_ occur together at Indianpoint Lake, British Columbia. Specimens taken there are readily sorted into two groups; none is intermediate. The difference in size between these species there is especially marked; _Z. p. saltator_ there is a large derivative of _Z. princeps_ and _Z. h. tenellus_ is a medium-sized _Z. hudsonius_.

_Z. princeps_ minor and _Z. hudsonius intermedius_ have been taken at several neighboring localities in North Dakota. Although these geographic races are more nearly of the same size (_minor_ is a small subspecies of _princeps_ and _intermedius_ is a moderately large subspecies of _hudsonius_) they do not interbreed. Specimens of _Z. p. minor_ and _Z. h. intermedius_ have been obtained from an ecologically homogeneous area in the vicinity of Fort Totten and Devils Lake, North Dakota. Values obtained from several measurements of the skull and baculum allow for ready recognition of the two species. The populations from North Dakota are, however, not so widely divergent as are those populations from the area of contact in British Columbia. Perhaps the difference in the degree of distinction between the species at the two areas of contact is indicative of the length and completeness of geographic isolation between neighboring populations.

The ranges of _Z. trinotatus_ and _Z. hudsonius_ are not at present in contact, but the two species differ more strongly than do _hudsonius_ and _princeps_ or _princeps_ and _trinotatus_. Therefore, _trinotatus_ and _hudsonius_ are here considered to be two distinct species.

As pointed out earlier in this discussion, the separation between the progenitors of _Z. trinotatus_ and _Z. princeps_ probably occurred when the present Cascade Range and the Sierra Nevada were being formed. From this time until Pleistocene glaciation an incomplete geographic isolation was in effect between the populations of the Pacific coast and the intermountain populations. Perhaps in the region north of the present Cascade Range there was moderate interbreeding between these populations and the transcontinental form. There may have been a similar zone of interbreeding along the crest of the present Cascades where the intermountain and coastal populations conceivably could have met. At least incipient characters probably were present when in Pleistocene time, continental glaciation further isolated the two populations. Since the retreat of the last ice (Wisconsin) the unprogressive coastal _Z. trinotatus_ has expanded its range only slightly, reaching as far as southwestern British Columbia. It seems that ecological difference rather than the barrier formed by the higher elevations is responsible for the limited expansion of range. The population of _princeps_ has extended its range northward to the southern part of the Yukon Territory but does not occur in coastal southern British Columbia because that area already was occupied by _Zapus trinotatus_. The ranges of the two species meet and overlap in southwestern British Columbia. The species occur sympatrically in Manning Park where, according to Carl _et al._ (1952:77), they occupy the same range in the region of Allison Pass, Pinewoods, and Timberline Valley. These workers remark that no intergradation was apparent between individuals of the two species obtained in the same trap line.

I have examined material of both species from Allison Pass. There the species differ in color, in the shape of the skull, and in the size and shape of the baculum. Material from Timberline Valley, an area in which Carl _et al._ (_loc. cit._) reported both species, here is assigned to _Z. princeps_. Where bacula have been preserved the identity of the species is instantly possible.

In summary: First, a population of jumping mice, possibly a monotypic genus, occurred over most of North America; then this population partly divided into Pacific northwest, intermountain (from the east slopes of the present Rocky Mountains to the east slopes of the present Cascade Range and the Sierra Nevada), and transcontinental (eastern and northern) groups with the least progressive groups peripheral; a further reduction or possibly a complete isolation of these populations followed owing to Pleistocene glaciation (especially in the Wisconsin period); and, finally, the present day contacts were established between these populations which by now have differentiated into species. Conceivably, _Z. burti_ (Blancan age) and _Z. rinkeri_ (mid Pleistocene) may represent stages in the development of _Z. hudsonius_.

ANNOTATED LIST OF SPECIFIC AND SUBSPECIFIC NAMES

(Applied to the genus _Zapus_ since 1899)

Edward A. Preble's (1899) early revisionary account of the genus _Zapus_ provides an annotated list of the names which had been proposed for American jumping mice to that date. The present account supplies in chronological order the names proposed (including the new kinds described by Preble) in the 54 years since Preble's revision. Detailed synonymies are given for each kind under the accounts of the subspecies.

1899 _campestris_ (_Zapus hudsonius_) Preble, N. Amer. Fauna, 15:20, August 8, 1899, applies to the jumping mouse of southeastern Montana, and the Black Hills region of Wyoming and South Dakota.

1899 _minor_ (_Zapus princeps_) Preble, N. Amer. Fauna, 15:23, August 8, 1899, originally applied to the jumping mouse of the prairies of Saskatchewan, but now includes populations of this species from the plains of Canada (southern Manitoba to Canadian Rockies) and northern United States (Montana, North and South Dakota).

1899 _oregonus_ (_Zapus princeps_) Preble, N. Amer. Fauna, 15:24, August 8, 1899, originally applied to the jumping mouse of eastern Oregon, but now applies also to populations from southeastern Idaho, eastern and central Nevada, and extreme northeastern California.

1899 _major_ (_Zapus_) Preble [= _Zapus princeps oregonus_], N. Amer. Fauna, 15:25, August 8, 1899, arranged as a subspecies of _Zapus princeps_ by Hall, Univ. California Publ. Zool., 37:10, April 10, 1931; here considered a synonym of _Zapus princeps oregonus_.

1899 _nevadensis_ (_Zapus_) Preble [= _Zapus princeps oregonus_], N. Amer. Fauna, 15:25, August 8, 1899, arranged as a subspecies of _Zapus princeps_ by Hall, Univ. California Publ. Zool., 37:10, April 10, 1931; here considered a synonym of _Zapus princeps oregonus_.

1899 _orarius_ (_Zapus_) Preble [= _Zapus trinotatus orarius_], N. Amer. Fauna, 15:29, August 8, 1899, applies to the animals from southwestern Marin County, California.

1911 _luteus_ (_Zapus_) Miller [= _Zapus princeps luteus_], Proc. Biol. Soc. Washington, 24:253, December 23, 1911, applies to the jumping mouse in north-central and southern New Mexico and eastern Arizona.

1913 _australis_ (_Zapus luteus_) Bailey [= _Zapus princeps luteus_], Proc. Biol. Soc. Washington, 26:129, May 21, 1913, was applied to the jumping mouse of southern New Mexico, but is here regarded as a synonym of _luteus_.

1920 _eureka_ (_Zapus trinotatus_) Howell, Univ. California Publ. Zool., 21:229, May 20, 1920, applies to the jumping mouse of the humid coastal district of northern California.

1931 _cinereus_ (_Zapus princeps_) Hall, Univ. California Publ. Zool., 37:7, April 10, 1931, applies to the jumping mouse of extreme northwest Utah and south-central Idaho.

1931 _curtatus_ (_Zapus princeps_) Hall, Univ. California Publ. Zool., 37:7, April 10, 1931, applies to the jumping mouse of the Pine Forest Mountains, Humboldt County, Nevada.

1931 _palatinus_ (_Zapus princeps_) Hall [= _Zapus princeps oregonus_], Univ. California Publ. Zool., 37:8, April 10, 1931, was applied to the jumping mouse of Lander and Nye counties, Nevada, but is here regarded as a synonym of _oregonus_.

1932 _kootenayensis_ (_Zapus princeps_) Anderson, Ann. Rept. Nat. Mus. Canada for 1931:108, November 24, 1932, applies to the jumping mouse of southeastern and central British Columbia, northern Idaho, and eastern Washington.

1934 _idahoensis_ (_Zapus princeps_) Davis, Jour. Mamm., 15:221, August 10, 1931, applies to populations in parts of British Columbia, Alberta, Idaho, Montana, and Wyoming.

1939 _utahensis_ (_Zapus princeps_) Hall, Occas. papers Mus. Zool. Univ. Michigan, 296:3, November 2, 1934, applies to the jumping mouse of southeastern Idaho, western Wyoming, and eastern Utah.

1941 _burti_ (_Zapus_) Hibbard, Univ. Kansas Publ., Bull. State Geol. Surv. Kansas, 38:214, July 14, 1941, refers to two fragmentary right rami of Pleistocene age (Borchers fauna) from Loc. No. 9, Meade County, Kansas.

1942 _brevipes_ (_Zapus hudsonius_) Bole and Moulthrop [= Zapus hudsonius americanus], Sci. Publ. Cleveland Mus. Nat. Hist., 5:168, September 11, 1942, based on specimens from Bettsville, Seneca County, Ohio, which are inseparable from _americanus_ that has priority.

1942 _rafinesquei_ (_Zapus hudsonius_) Bole and Moulthrop [= _Zapus hudsonius americanus_], Sci. Publ. Cleveland Mus. Nat. Hist., 5:169, September 11, 1942, was applied to jumping mouse of southeastern Ohio but is here regarded as a synonym of _americanus_.

1943 _ontarioensis_ (_Zapus hudsonius_) Anderson [= _Zapus hudsonius canadensis_], Ann. Rept. Provancher Soc. Nat. Hist., Quebec, 1942:52, September 7, 1943, was applied to animals from eastern Ontario but is here regarded as a synonym of _canadensis_.

1950 _pallidus_ (_Zapus hudsonius_) Cockrum and Baker, Proc. Biol. Soc. Washington, 63:1, April 26, 1950, refers to the jumping mouse from Kansas, Missouri, Oklahoma, Nebraska, and south-central South Dakota.

1951 _rinkeri_ (_Zapus_) Hibbard, Jour. Mamm., 32:351, August, 1951, refers to single incomplete right ramus of upper Pliocene age, Rexroad formation and fauna, from Loc. UM-UK-47, Fox Canyon, sec. 25, T. 34S, R. 30W, XI Ranch, Meade County, Kansas.

1953 _intermedius_ (_Zapus hudsonius_) described as new on page 447 of this paper.

1953 _preblei_ (_Zapus hudsonius_) described as new on page 452 of this paper.

CHARACTERS OF TAXONOMIC WORTH

EXTERNAL PARTS.--The total length, the length of the tail, and the length of the hind foot are useful to some extent in distinguishing species and subspecies. Geographic variation in these measurements is clinal in some species. For example, _Zapus trinotatus_, which inhabits the western coast of North America, decreases in size from the northern to the southern part of its range. There is considerable overlap in external measurements, in specimens of the same age, between the species _Z. trinotatus_ and _Z. princeps_, but only slight overlap between _Z. princeps_ and _Z. hudsonius_ and between _Z. trinotatus_ and _Z. hudsonius_. If all collectors measured external parts in the same way the measurements would be more useful for differentiating one species from another.

PELAGE.--The pelage, both in its entirety and as individual hairs, provides taxonomic characters as has been pointed out by Moojen (1948:324) for the genus _Proechimys_, by Williams (1938:239) for the Insectivora, and by Hausman (1920:496) for several groups of mammals. In addition to the sensory hairs, facial vibrissae, nasal hairs, and carpal vibrissae, there are three kinds of hairs in the normal coat of _Zapus_: guard hairs, overhairs, and underfur. The guard hairs and underfur differ in different species (see figs. 35-37).

The guard hairs taper at both ends, are elliptical in cross section, and are wider and longer than the other two kinds of hair. The bases of the guard hairs are grayish, and the amount of pigment gradually increases distally to a dark brownish or blackish shade. The guard hairs vary in greatest diameter from 96 microns to 168 microns, depending upon the species, and variation in diameter provides characters of taxonomic worth. No clinal variation in diameter of the guard hairs was detected. In _Z. hudsonius_ the guard hairs average 115 microns (96-140) and are significantly narrower than those of _Z. princeps_ and _Z. trinotatus_, which average 142 microns (130-168) and 141 microns (133-154), respectively. Pigmentation of the guard hairs contributes little information useful in separating the species of _Zapus_. All of the species have a prominent compounded medulla in which the pigment cells anastomose to form a labyrinthine column.

The individual hair of the underfur is cylindrical and tapers abruptly at each end; it is short, thin, flexible, and usually is bicolored on the back and sides of the mouse. The apical zone is yellow-brown (for example, Ochraceous-Buff) and the proximal part is whitish or grayish, which gradually darkens to near black subapically.

The width of a hair in the underfur is of no taxonomic significance, in that individual variation exceeds that between species.

The pattern of the pigment in the medulla of the hair, however, does vary specifically. Comparable samples from _Z. trinotatus_, _Z. princeps_, and _Z. hudsonius_ of the same age, sex, and season reveal a pattern characteristic for each species (see figs. 35-37).

All species of _Zapus_ agree closely in color pattern. A broad longitudinal dorsal band of some shade of yellow-brown flecked with black hairs is bordered by a lateral band of a lighter color usually containing fewer black hairs than on the dorsum. The underparts are usually white but are sometimes suffused with color resembling that on the sides. Between the white underparts and the darker color of the sides there is often a narrow, clear ochraceous stripe. Dorsal and lateral hairs are uniformly grayish-white at their bases; only the distal parts of the hairs are responsible for the external color of the animal.

The pelage of juveniles is usually finer and softer than the pelage of adults. The lateral and dorsal bands are not so conspicuously marked in young animals, and individual hairs are not so long or so wide as in adult animals.

Preble (1899:7) and Howell (1920:226) remark as to the noticeable difference between pelages of spring and early fall. The pelage in spring is described as bright and fresh whereas that in fall is dull and worn. Actually both bright and worn pelages can occur in any one population at any one time. Some newly molted individuals are in fresh unworn pelage; some individuals, which are molting, are in ragged, worn pelage; and other individuals perhaps could be found to represent intermediate stages.

Variations from the normal color of the pelage are rare. Among more than 3,000 specimens of _Zapus_ examined there were only 12 individuals (five _Z. princeps_, 6 _Z. hudsonius_, and 1 _Z. trinotatus_) that were abnormally colored. A single white spot was noted on each of 10 (5 _Z. princeps_, 4 _Z. hudsonius_, and 1 _Z. trinotatus_) of these individuals; the spots were on the dorsal, anterior half of the body. The skin beneath the patch of white hair was in each animal like that beneath the neighboring normally-pigmented hair. One specimen of _Z. hudsonius_ (NMC No. 6669) is everywhere black, excepting the dorsal surface of the toes of the forefeet. Most of the individual hairs from various areas of the body are black for their entire length; some, however, have non-pigmented silvery tips. One specimen of _Z. hudsonius_ (KU No. 645) lacks any black; dorsally the pelage is nearest to Ochraceous-Buff and it is white on the venter. Individual hairs of the dorsal area are white for the basal two-thirds of their length (as compared to gray and brown in the animals with normal pigmentation) and near Ochraceous-Buff on the distal third (as compared to hairs which are dark brown tipped with Ochraceous-Buff). The feet and tail are white.

MOLT.--The sequence of molt for _Zapus_ has been ascertained from examination of the study skins. In all species of this genus there seems to be only one annual molt in adults. In the young of the year this molt occurs after August first and before hibernation. All individuals of a single population do not molt at any one time; females continue to molt later in the autumn than do the males; some individuals begin the molt as early as mid-June and others show molt as late as the end of October; approximately three weeks are required for an individual to complete its molt (Quimby, 1951:74); readiness for molt and early stages in molt can be detected (in museum specimens) by the greater thickness of the skin. Hairs lost accidentally are quickly replaced, regardless of the condition of the molt.

In _Zapus hudsonius_, new hair appears simultaneously on the anterior dorsal surface of the nose and on the mid-dorsal surface between the scapulae. The molt proceeds anteriorly from the shoulders and posteriorly from the nose. At the same time that the head is covered, new hair appears on the sides of the body from the forelegs to the cheeks. New pelage then appears posteriorly, and molt continues as a wave from these points over the sides and back with the rump receiving new hair last (see figs. 42 and 43).

In _Zapus princeps_ new hair appears first on the mid-dorsal surface between the scapulae. From this starting point molt progresses anteriorly, laterally, and posteriorly. Progress over the head is rapid; the head receives its new hair sooner than the caudal region. Molt moves progressively nearer to the base of the tail and progressively nearer to the mid-ventral surface. The rump is the last area to complete its molt (see figs. 40 and 41).

The progress of molt in _Z. princeps_ might be likened to the flow of a drop of paint on the curved surface of a ball where the paint flows in all directions but is speeded at one point and slowed at the opposite by a slight tilting of the ball from the horizontal.

In the species _Zapus trinotatus_ new hair appears simultaneously on the anterior, dorsal surface of the nose and on the mid-dorsal surface between the scapulae. In this respect the progress of molt of _Z. trinotatus_ resembles that of _Z. hudsonius_. From these starting points molt progresses rapidly over the head, the molt moving anteriorly from the shoulders and posteriorly from the nose with the result that it covers the dorsal surface of the head; hair then appears on the cheeks and sides of the neck. The progress of molt on the remaining areas of the body is comparable to that of _Z. princeps_; molt progresses toward the tail and toward the mid-ventral line. The rump, as in _Z. princeps_, is the last area to complete its molt (see figs. 38 and 39).

BACULUM.--The general shape and dimensions of the baculum (os penis) provide characters of taxonomic value for the species of _Zapus_ (see figs. 23-25 and figs. 28-30).

Three measurements--length, transverse diameter at the base, and transverse diameter at the tip--are easily obtained and are diagnostic. The bacula of all species are somewhat curved. The measurement of length used by me does not represent the actual length of the bone, but instead the chords of the arcs involved.

SKULL.--Some of the structures useful for separating taxonomic entities may have little or no biological significance to the animals in nature. Characters mentioned by me are chosen simply for their significance taxonomically. The zygomata vary in degree of lateral bowing, being widely bowed in _Z. princeps_ and _Z. trinotatus_, and less so in _Z. hudsonius_. Differences in zygomatic breadth owing to the degree of bowing are an aid in differentiating subspecies. The length of the skull from the occipital condyles to the tip of the longest nasal bone is useful in separating _Z. hudsonius_ from _Z. trinotatus_ and _Z. princeps_. The narrowness of the base of the zygomatic process of the squamosal is useful in distinguishing between _Z. hudsonius_ and _Z. princeps_, but shows no variation of subspecific worth. The shape and dimensions of the incisive foramina provide specific and subspecific characters. The position of the anterior margin of the postpalatal notch, in relation to the last molars, provides subspecific characters in _Z. princeps_. In the species _Z. princeps_ the median projection on the inferior ramus of the zygomatic process of the maxillary is absent in some subspecies, small in others, and large in some. Shape and inflation of the auditory bullae, shape of the pterygoid fossae, and shape of the nasals are useful in determining specific and subspecific relationships.

TEETH.--The alveolar length of the upper maxillary tooth-rows aids in distinguishing _Z. hudsonius_ from _Z. princeps_ and _Z. trinotatus_. Nearly parallel versus anteriorly divergent upper tooth-rows is a subspecific difference in _Z. princeps_. Variations in the dimensions of P4 and M1 aid in estimating the relationships of species. The occlusal pattern shows little variation and was of no use in separating species.

NONGEOGRAPHIC VARIATION

A knowledge of variation resulting from age, individual, or secondary sexual differences, as opposed to geographic variation between two or more populations of a single species is important in determining the reliability of taxonomic characters.

The largest population-sample of _Zapus_ available to me for the study of nongeographic variation was 63 individuals from various localities in Keweenaw and Menominee counties, Michigan. Thirty-nine were females and 24 were males. It is on these specimens that this discussion is based.

Age Variation

TEETH.--The teeth provide a valuable standard for age determination in that they wear at a measurable rate. The molars erupt in sequence from front to back, and wear shows first on M1 and last on M3. The peglike permanent P4, of which I have not seen the deciduous precursor, receives wear at the same time that the molars are being worn. Wear proceeds at approximately the same rate in the teeth of both the upper jaws and lower jaws.

In order to be more nearly certain that specimens used in making racial comparisons were comparable as to age, six age-groups were established, from youngest to oldest. These groups were based on the degree of wear on the occlusal surface of the upper cheek-teeth, and are as follows: group 1, in which M1 and M2 have not reached full and equal height and show no occlusal wear, and M3 has not erupted or is just breaking through the alveolus; group 2, in which M1 and M2 have reached full and equal height and show slight wear, and M3 may be almost or quite equal in height to M1 and M2 and, when equal, sometimes shows slight wear; group 3, in which M1 and M2 show wear on all cusps but cusps are visible, and M3 shows slight wear; group 4, in which P4 shows slight wear, M1 has cusps and re-entrant folds between cusps mostly gone, M2 shows considerable wear but re-entrant folds are visible, and M3 has most re-entrant folds and cusps gone; group 5, in which P4 shows considerable wear, M1 has cusps completely worn away, M2 has re-entrant folds and cusps worn away, and M3 lacks occlusal pattern except for one or two lakes; group 6, in which all upper cheek-teeth are without occlusal pattern.

These groupings are based on continuously variable features, and, therefore, when the teeth are at certain stages of wear a specimen is difficult to place in one of two groups.

Age group 1 and 2 include juvenal and subadult animals. Animals of age groups 3 through 6 are considered adult. Individuals of age groups 3 through 5, including as they do the great majority of the adult population, were the only age classes used in measuring geographic variation.

Quimby's (1951:69) data indicate that some mice produce litters at the age of approximately 2 months, when four-fifths grown. Therefore, sexual maturity is not always synonymous with morphological maturity.

MEASUREMENTS OF EXTERNAL PARTS.--Data presented here on _Z. hudsonius_ are those recorded by Quimby (1951) on specimens from Anoka County, Minnesota, and those obtained by me from museum specimens from Menominee and Keweenaw counties, Michigan.

According to Quimby (1951:65-66) the mean length [= body length] for three newly born _Z. hudsonius_ is 24.8 mm (24.0-25.5); at the end of the fourth week of growth the mean length averaged 64.4 mm and at the 13th week 77.6 mm. Rapid growth occurs during the first four weeks, with the mean length increasing approximately 2.6 times the size at birth. After the fourth week of development, growth proceeds at a slower rate; the mean length at 13 weeks is only 3.1 times greater than the mean length at birth.

In specimens assigned to age groups 1 and 2 the length of the body averaged 70 and 74.8 mm, respectively. The individuals of both groups are less than 13 weeks old if we assume that growth proceeds at the same rate in Michigan as it does in Minnesota.

In the specimens from Michigan of age groups 3, 4, 5, and 6 the average length of the body is 80.9, 83.7, 89.0, and 83.6, respectively.

According to Quimby (_loc. cit._), the average length of the tail for three _Z. hudsonius_ at birth was 9.2 mm. (8.5-10.0). During the first four weeks of development the tail grew rapidly and reached an average length of 92.0 mm, which was 10 times the length at birth. By the end of 13 weeks of development the average length of the tail for these three individuals was 119.6 mm or 12 times the average length at birth. The most rapid growth was early in development: 80 per cent of the growth of the tail occurred during the first month, after which growth proceeded at a much slower rate.

Quimby (_loc. cit._) records an average dimension of 4.7 mm (4.5-5.0) for the length of the hind foot in three newly born _Z. hudsonius_. The hind foot grew rapidly in length and by the fourth week had increased 5.6 times in its length and averaged 26.3 mm. Growth was much less rapid from the fourth to the thirteenth week when the hind foot averaged 27.7 mm, only five per cent more than in mice four weeks old. Assuming the average length of the hind foot of the adults to be 29.0 mm, the hind foot in individuals 13 weeks old is 96 per cent of the adult size.

According to Quimby (_loc. cit._), the pinna of the ear at birth is small and folded over the external auditory meatus. The length of the ear increases proportionately more (29 per cent) than any other external dimension after the first four weeks of growth.

If the average length of the ear (measured from the crown) of adults is 14.7 mm, the animals from Michigan in age groups 1 and 2 are 91.8 per cent and 96.5 per cent as large as adults.

TABLE 1.--Average Dimensions (in Millimeters) for Specimens of Z. h. hudsonius of Various Ages (Specimens from Michigan).

==============+=======+=======+=======+=======+=======+======= Age groups | 1 | 2 | 3 | 4 | 5 | 6 --------------+-------+-------+-------+-------+-------+------- No. examined | 4 | 13 | 33 | 12 | 3 | 3 --------------+-------+-------+-------+-------+-------+------- Body | 70.0 | 74.8 | 80.9 | 83.7 | 89.0 | 83.6 --------------+-------+-------+-------+-------+-------+------- Tail | 113.8 | 118.5 | 122.9 | 125.0 | 125.0 | 118.3 --------------+-------+-------+-------+-------+-------+------- Hind foot | 28.8 | 28.6 | 28.9 | 29.1 | 28.9 | 29.3 --------------+-------+-------+-------+-------+-------+------- Ear | 13.5 | 14.2 | 14.7 | 14.8 | 15.0 | 14.3 --------------+-------+-------+-------+-------+-------+-------

From these data, concerning growth of external parts, it seems that: growth is most rapid during the four weeks following parturition; specimens from Michigan, assigned to age groups 1 and 2 on the basis of tooth wear, are less fully developed and probably younger than mice from Minnesota, with a known age of 13 weeks; individuals with sufficient wear on the teeth to be placed in age group 3, if they were obtained in the late fall, may be young from the first litters of the year or, if they were obtained in early spring, may be at least one year old; individuals in age groups 4, 5, and 6 are at least one year old.

SKULL.--The post-embryonic development of the skull is rapid. Animals in age groups 1 and 2 have skulls which average more than 80 per cent of the size that is here considered adult (an average size obtained from age groups 3, 4, and 5). The actual increase in size of certain cranial elements for various age groups is given in table 2.

In age group 1 the rostrum is relatively short as it is in _Neotoma micropus_ (J. A. Allen, 1894:235) and juveniles of _Peromyscus truei_ (Hoffmeister, 1951:7). The rostrum lengthens rapidly and there is a general increase in actual and relative size of the entire preorbital region; the increase after age group 3 is slower and of lesser magnitude. Changes with age in the size of the braincase are slight. In age group 1 the average depth of the braincase is 99.6 per cent of the adult size; the average breadth of the braincase is 98 per cent of the adult size, and the average width across the mastoid region is 96.4 per cent of the adult size. These dimensions indicate that the braincase reaches full size early. The zygomatic arch, however, undergoes change with age; there is a gradual increase in breadth owing to lateral bowing and a gradual lengthening which is in keeping with a general elongation of the skull anterior to the braincase.

The incisive foramina in age group 1 are short (4.0 mm), broad (2.2 mm in the middle), and taper to a point at each end. In age group 2 the foramina have elongated (4.2 mm) and are less pointed posteriorly, but there is no change in breadth. In age groups 3, 4, 5, and 6 the foramina become progressively longer (4.5 mm in age group 6), have a relatively constant breadth (2.2 mm), and become more nearly truncate anteriorly.

TABLE 2.--Average and Extreme Measurements (in Millimeters) of Skulls of Six Age-groups in Specimens of Zapus hudsonius from Michigan.

===============+============+============+============ Age groups | 1 | 2 | 3 ---------------+------------+------------+------------ Number | | | examined | 4 | 13 | 33 | | | Occipitonasal | 20.5 | 21.2 | 22.0 length | 20.0 21.2 | 20.8 21.8 | 21.5 23.2 | | | Mastoid | 9.8 | 10.04 | 10.12 breadth | 9.7 10.0 | 9.6 10.4 | 9.5 10.5 | | | Length of | 8.07 | 9.02 | 9.07 zygomatic arch | 8.0 8.2 | 8.5 9.3 | 8.5 9.4 | | | Breadth of | 3.36 | 3.33 | 3.37 palate at P4 | 3.3 3.5 | 3.1 3.4 | 3.1 3.8 | | | Breadth of | 2.4 | 2.55 | 2.66 palate at M3 | 2.3 2.6 | 2.3 2.7 | 2.3 3.2 | | | Palatal | 8.67 | 8.98 | 9.38 length | 8.4 9.1 | 8.8 9.2 | 9.3 9.8 | | | Distance from | | | incisors to | 8.53 | 8.98 | 9.08 postpalatal | 8.4 8.7 | 8.5 9.5 | 9.0 9.8 notch | | | | | | Interorbital | 4.25 | 4.19 | 4.2 breadth | 4.2 4.3 | 4.0 4.4 | 4.0 4.4 | | | Average length | | | of upper | 3.2 | 3.2 | 3.21 molar series | 3.2 3.4 | 3.2 3.4 | 2.9 3.5 | | | Breadth of | 9.5 | 9.58 | 9.61 braincase | 9.3 9.7 | 9.2 9.7 | 9.1 10.0 | | | Zygomatic | 10.33 | 10.49 | 10.55 breadth | 10.0 10.7 | 10.4 10.9 | 10.1 11.2 | | | Condylobasal | 16.9 | 18.33 | 18.80 length | 16.6 17.1 | 17.4 19.2 | 18.2 19.5 ---------------+------------+------------+------------

===============+============+============+============ Age groups | 4 | 5 | 6 ---------------+------------+------------+------------ Number | | | examined | 14 | 3 | 3 | | | Occipitonasal | 22.7 | 22.9 | 23.0 length | 21.8 23.4 | 22.7 23.3 | 22.4 23.7 | | | Mastoid | 10.12 | 10.3 | 10.36 breadth | 9.6 10.7 | 10.0 10.8 | 10.1 10.8 | | | Length of | 9.25 | 9.5 | 9.35 zygomatic arch | 9.2 9.4 | 9.5 9.5 | 9.1 9.6 | | | Breadth of | 3.44 | 3.66 | 3.45 palate at P4 | 3.1 3.7 | 3.6 3.7 | 3.4 3.5 | | | Breadth of | 2.74 | 3.11 | 2.77 palate at M3 | 2.5 3.0 | 3.0 3.2 | 2.6 2.9 | | | Palatal | 9.59 | 9.73 | 9.8 length | 9.0 10.0 | 9.5 9.9 | 9.6 10.1 | | | Distance from | | | incisors to | 9.68 | 9.73 | 9.80 postpalatal | 9.2 10.0 | 9.5 9.9 | 9.6 10.1 notch | | | | | | Interorbital | 4.2 | 4.23 | 4.2 breadth | 4.0 4.4 | 4.1 4.4 | 4.2 4.2 | | | Average length | | | of upper | 3.22 | 3.2 | 3.16 molar series | 2.9 3.5 | 3.2 3.2 | 3.1 3.2 | | | Breadth of | 9.68 | 9.83 | 9.63 braincase | 9.3 10.0 | 9.5 10.2 | 9.3 9.9 | | | Zygomatic | 10.80 | 11.0 | 11.25 breadth | 10.7 11.2 | 10.5 11.5 | 11.2 11.3 | | | Condylobasal | 19.33 | 19.6 | 19.9 length | 18.5 19.9 | 19.4 19.8 | 19.5 20.3 ---------------+------------+------------+------------

Individual Variation

Measurements of external parts in _Zapus_ are more variable than are measurements of most parts of the skull. As Hoffmeister (1951:16) points out for _Peromyscus truei_, this variation in external features results in part from "the difficulties in accurately measuring soft parts of the anatomy" and also from inconsistencies on the part of collectors in making these measurements.

A comparison of coefficients of variation (see table 3) for cranial measurements between populations of like age and sex for the species _Z. hudsonius_, _Z. princeps_, and _Z. trinotatus_ shows that variation of approximately the same degree is recorded in corresponding elements in all species; that is to say, structures which are most variable individually in _Z. princeps_ are also most variable in _Z. trinotatus_ and _Z. hudsonius_.

Individual variation in the occlusal pattern of the molariform teeth is slight. In several specimens, however, the re-entrant fold is absent from the lingual surface of M1. Teeth in addition to the normal number were recorded for five specimens. In all instances they are in the upper dentition and usually at the posterior end of the maxillary tooth-row. In each of four specimens (KU No. 34852, KU No. 32852, MVZ No. 52105, all _Z. princeps_, and USBS No. 22921, _Z. hudsonius_), there is only a single additional tooth. One individual (USBS No. 264388, _Z. princeps_) possessed two extra molars, one in each maxillary tooth-row. The extra teeth vary in size from those which are only slightly smaller than the adjacent normal molars to those which are simple, peglike structures. In four of the five animals the extra teeth are posterior to the normal M3; in the fifth (MVZ No. 52105) the added tooth is anteriormedial to M3.

TABLE 3.--Coefficients of Variation for Dimensions of Corresponding Parts of the Skull of Three Species of Zapus. The Specimens of Zapus hudsonius are from Menominee and Keweenaw counties, Michigan, the Zapus princeps are from the Vicinity of Encampment, Wyoming, and the Zapus trinotatus from Huntingdon, British Columbia.

==============================+=============+============+============== | _Z. h._ | _Z. p._ | _Z. t._ Species | _hudsonius_ | _princeps_ | _trinotatus_ ------------------------------+-------------+------------+-------------- No. examined | 52 | 46 | 19 | | | Mastoid width | 2.85 | 1.98 | 2.21 | | | Occipitonasal length | 2.64 | 1.37 | 1.20 | | | Incisors to postpalatal notch | 3.02 | 2.56 | 2.56 | | | Interorbital constriction | 2.75 | 3.66 | 3.22 | | | Zygomatic breadth | 2.74 | 2.54 | 1.94 | | | Maxillary tooth-row | 4.50 | 4.44 | 3.82 ------------------------------+-------------+------------+--------------

The size and shape of certain cranial elements vary individually even between right and left sides of the same animal. The paired parietal bones in some animals are nearly square and identical. In other animals these bones are approximately equal and straight on three sides with the fourth side forming an anterolateral projection; this projection may be slightly or greatly produced, and opposite elements in a single individual differ in this respect.

The interparietal also is variable; the lateral arms may be blunted and not included in the fusion of the squamosal, parietal, and occipital elements, or the interparietals may be elongated and fused with these elements. Posterior and anterior borders of the interparietal may be straight, produced anteriorly, produced posteriorly, or produced anteriorly and posteriorly.

There is frequently variation in the degree of taper of the nasals. They may be parallel sided, narrowed distally, or narrowed proximally. There is some variation in the degree of inflation, in the size, and in the shape of the frontal bones. The anterior surface of the postpalatal notch varies individually and may be truncate, anteriorly convex, or anteriorly concave.

Individual variation in the color of the pelage of animals that are in the same stage of molt or non-molt is by my observation slight. The presence of oil in the hair results in a false impression of sleekness and seemingly darker pigmentation. Abnormal white-spotting dorsally occurs as does yellow and melanistic coat color. These mutations are considered in the discussion concerning pelage.

Secondary Sexual Variation

In specimens of the two sexes from similar age groups of _hudsonius_ from Michigan, the mean values for each measurement for the two sexes differ only slightly or are essentially the same (see table 4). In no species has secondary sexual variation been found to be greater than individual variation.

TABLE 4.--Mean Measurements for Adult Male and Female Z. hudsonius of Age Group 2 and Per Cent Difference of Females to Males (Specimens from Michigan).

==============================+=========+=========+===================== | | | Per cent difference, Sex | Male | Female | females to males ------------------------------+---------+---------+--------------------- No. examined | 18 | 15 | | | | Total length | 202.85 | 202.88 | 0.02% larger | | | Hind foot | 122.85 | 122.10 | 0.60% smaller | | | Mastoid width | 10.10 | 10.28 | 1.50% larger | | | Occipitonasal length | 22.15 | 22.03 | 0.55% smaller | | | Incisors to postpalatal notch | 9.39 | 9.33 | 0.64% smaller | | | Zygomatic breadth | 10.47 | 10.57 | 0.95% larger | | | Maxillary tooth-row length | 3.52 | 3.60 | 0.23% larger ------------------------------+---------+---------+---------------------

CHECK-LIST OF THE SPECIES AND SUBSPECIES OF THE GENUS _ZAPUS_

PAGE

_Zapus trinotatus_ 385 _Zapus trinotatus eureka_ A. B. Howell 389 _Zapus trinotatus montanus_ Merriam 390 _Zapus trinotatus orarius_ Preble 391 _Zapus trinotatus trinotatus_ Rhoads 392

_Zapus princeps_ 394 _Zapus princeps cinereus_ Hall 399 _Zapus princeps curtatus_ Hall 400 _Zapus princeps idahoensis_ Davis 401 _Zapus princeps kootenayensis_ Anderson 404 _Zapus princeps luteus_ Miller 406 _Zapus princeps minor_ Preble 407 _Zapus princeps oregonus_ Preble 409 _Zapus princeps pacificus_ Merriam 412 _Zapus princeps princeps_ Allen 414 _Zapus princeps saltator_ Allen 416 _Zapus princeps utahensis_ Hall 418

_Zapus hudsonius_ 420 _Zapus hudsonius acadicus_ (Dawson) 432 _Zapus hudsonius alascensis_ Merriam 435 _Zapus hudsonius americanus_ (Barton) 436 _Zapus hudsonius campestris_ Preble 441 _Zapus hudsonius canadensis_ (Davies) 442 _Zapus hudsonius hudsonius_ (Zimmerman) 443 _Zapus hudsonius intermedius_ Krutzsch 447 _Zapus hudsonius ladas_ Bangs 449 _Zapus hudsonius pallidus_ Cockrum and Baker 450 _Zapus hudsonius preblei_ Krutzsch 452 _Zapus hudsonius tenellus_ Merriam 453

Genus =Zapus= Coues

_Genotype._--_Dipus hudsonius_ Zimmerman.

EXTERNAL CHARACTERS.--Muriform in general appearance; forelimbs small, short; hind limbs greatly developed; hind feet long and narrow; tail tapering, attenuate, subcylindrical; head long and mouse-shaped; eyes small and situated midway between nose and ear; external ear somewhat longer than surrounding hair and provided with antitragal flap which can cover external auditory meatus, and in company with tragus completely close opening; upper lip without median groove; internal cheek-pouches well developed and opening at corners of mouth; mystacial vibrissae conspicuous; supercilliary vibrissae few; genal tuft absent; teats normally eight and arranged in pairs (one pectoral, two abdominal, and one inguinal); anterior and posterior pairs frequently undeveloped; general pelage coarse; color of pelage varies somewhat in different species but always follows single basic pattern of broad dorsal band of some shade of brown or brownish-yellow darkened with brownish-black, sides of a lighter tone and slightly streaked with brownish-black, underparts snow-white, sometimes suffused with color of the sides and usually separated from color of sides by sharp line of clear brownish-yellow; backs of forefeet and hind feet grayish-white; tail distinctly bicolor, dark brown above and yellowish-white below; ears dark and narrowly edged with light color.

CRANIAL CHARACTERS.--Skull short in relation to width, deep relative to other dimensions, somewhat convex; delicate, papery, without strong angularity; braincase relatively unexpanded; antorbital foramen obliquely oval and transmits masseter muscle of great size; foramen in inferior ramus of zygomatic process of maxillary for passage of superior maxillary branch of trigeminal nerve small; zygomata not wide-spreading; underside of zygoma nearly horizontal, upper edge anteriorly rises prominently owing to extension of jugal upward along maxillary; jugal and lachrymal in contact; one ramus of zygomatic process of maxilla arises directly above other; rostrum thick basally and relatively attenuate distally; ends of nasals project noticeably beyond incisors; premaxillaries develop strong alveolar plate separating superior incisors for half their length; palatal bones shortened posteriorly, free edge often concave; incisive foramina long, broad, and separated by bulbose (except at posterior end) bony septum; mastoid bullae absent; auditory bullae short and transversely placed; postorbital process never present; parietals nearly square, sometimes emarginate in front; angle of mandible flattened and bent inward; coronoid process weak, acute, and slopes strongly upward.

DENTAL CHARACTERS.--Dental formula

I 1, C O, P 1, M 3 -- -- -- -- -- -- -- -- = 18; i 1 c o p o m 3

upper incisors short, compressed, curved backward, and strongly grooved; lower incisors slender, curved backward, and ungrooved; both upper and lower incisors deep orange or yellow; four upper cheek-teeth present; premolar small, single rooted and, sometimes, non-functional; upper molars tri-rooted, sub-hypsodont, and with occlusal surface non-cuspidate (flat); enamel pattern, much complicated, consisting of one main re-entrant fold lingually and four re-entrant folds labially; three lower molars, bi-rooted, sub-hypsodont, flat crowned, with two outer and four inner re-entrant folds.

POSTCRANIAL CHARACTERS.--Neck short and weak; atlas large; axis separate from atlas; remaining (5) cervical vertebrae also free; thoracic (12) and lumbar (7) vertebrae strongly built; posterior lumbars with enlarged neural and anteriorly directed transverse processes; sacral vertebrae (7) as in murids; caudal vertebrae variable in number (average 36); clavicle long, slender, uniformly curved, convex outwardly; scapula with supraspinous and infraspinous fossae of equal size; forelimbs short, approximately half as long as hind limbs; hind limbs elongate, slender; femur with third trochanter; tibia and fibula fused slightly distal to middle of former; five elongate, separate metatarsals (first and fifth subequal, shorter than others).

ARTIFICIAL KEY TO THE SPECIES OF THE GENUS ZAPUS

A. Baculum with tip spade-shaped and tip wider than 0.43 mm; underfur with medullary pattern rectangular, cuticular scales small; coronoid process of mandible long and slender, angle of divergence from condyle broad; angle of mandible turned in and wide; pterygoid fossae wide; skull broad in relation to length; premolars with crescentine fold on occlusal surface. _Zapus trinotatus_ p. 385

A´. Baculum with tip lanceolate (not spade-shaped) and tip less than 0.43 mm wide; underfur with medullary pattern square or rectangular; but, if rectangular, cuticular scales large; coronoid process short and broad, angle of divergence from condyle narrow; angle of mandible turned inward and small to medium; pterygoid fossae usually narrow; skull not broad in relation to length; premolars without crescentine fold on occlusal surface.

B(A´). Baculum less than 5.1 mm in total length; guard hair averaging 115 micra in diameter; underfur with rectangular medullary pattern, cuticular scales large; skull small; incisive foramina shorter than 4.6 mm; condylobasal length averaging less than 20 mm; length of maxillary tooth-row averaging less than 3.7 mm; palatal breadth at M3 less than 4.2 mm. _Zapus hudsonius_ p. 420

B´. Baculum more than 5.1 mm in total length; guard hair averaging more than 140 micra in diameter; underfur with square medullary pattern, cuticular scales moderately large; skull large; incisive foramina longer than 4.7 mm; condylobasal length more than 21 mm; maxillary tooth-row averaging more than 3.8 mm; palatal breadth at M3 more than 4.4 mm. _Zapus princeps_ p. 394

SYSTEMATIC ACCOUNTS OF SPECIES AND SUBSPECIES

=Zapus trinotatus= Rhoads

(Synonymy under subspecies)

_Range._--From southwestern British Columbia southward through western Washington and Oregon and in the humid coastal district of California almost to the Golden Gate (see fig. 45).

_Characters of the species_: _External._--Size medium to large (total length 221 mm to 238 mm); tail longer than head and body (131 mm to 149 mm) and bicolored, brown above, white to yellowish-white below; hind feet long (31 mm to 34 mm), grayish-white above; back various hues and tones of ochraceous and tawny; sides paler than back; lateral line separating sides from ventral surface usually distinct and bright; ventral coloration white, usually with suffusion of ochraceous; ears usually dark, sometimes flecked, and usually narrowly edged with color of sides; guard hairs average 141 microns (133u to 155u) in diameter; underhair with medullary pigment in narrow, hollow rectangles; cuticular scales of underhair smaller and more numerous than in other species.

_Baculum._--Size large (total length 6.7 mm to 7.4 mm); base broad (0.7 mm to 0.9 mm); tip broad (0.44 mm to 0.57 mm); spade-shaped in dorsal aspect and tilted upward, gradually tapering to thin-edged tip; shaft rounded, straight.

_Skull._--Large, broad and deep in relation to length; pterygoid fossa broad; anterior ramus of zygomatic process of maxillary relatively narrow; nasofrontal juncture relatively broad; coronoid process of mandible elongate. Upper premolars relatively large (averaging .70 mm in length and .75 mm in width), usually functional, occlusal surface with labial re-entrant fold forming crescentine loop incompletely enclosing single central cusp; m3 relatively large, elongated; m1 elongated, broadly rounded anteriorly.

GEOGRAPHIC VARIATION

There are four subspecies currently recognized, all of which are confined to the Pacific coastal region of North America (See fig. 45). The features that vary geographically are external size, color of pelage (shade and tone of upper parts and tint of lower parts), and dimensions of certain cranial structures (zygomata, braincase, incisive foramina, palatal bridge, auditory bullae, and pterygoid fossae).

External size is smallest in the southernmost geographic race (_Z. t. orarius_) and largest in the northernmost geographic race (_Z. t. trinotatus_). This decrease in size from north to south is clinal and is in keeping with Bergman's Rule which postulates that within one species the smallest individuals occur in the warmer parts of its geographic range.

Coloration of pelage is geographically variable. There is a gradual change in the color of the pelage from north to south. Animals obtained in the northern part of the geographic range of _Z. trinotatus_ are generally darker dorsally (more tawny) with the ventral pelage usually pure white. Those individuals from the southern part of the geographic range of _Z. trinotatus_ have the dorsal pelage lighter (more reddish and yellow-brown) and ventrally the pelage is usually heavily suffused with reddish-brown. The crania also vary geographically; they are largest in the northernmost part of the range of the species and smallest in the southernmost part.

NATURAL HISTORY

_Habitat._--On the Olympic Peninsula, Washington, in 1931 Svihla and Svihla (1933:132) found this species equally abundant in alpine meadows near timberline, in open grassy areas, and in tall meadow grass and low blueberry bushes. All of the mice were in wet marshy places. Bailey (1936:232) reported that in Oregon, these mice live in meadows, marshes, under ferns and weeds in the woods, or near mountain brooks and streams. Taylor (1922:221) found _Zapus_ in moderately moist meadows in the Hudsonian Life-zone at Mt. Rainier, Washington, and Dice (1932:49) found them in deciduous forest and in open, grassy, or sphagnum bogs. Dice records it as common also among the alders and willows in high, open, grassy parks. Merriam (1897b:223) found _Z. trinotatus_ abundantly in moist places grown-over with grass or weeds. Grass cuttings two to three inches long were left in small heaps at feeding sites and indicate the presence of these mice.

_Behavior._--Svihla and Svihla (1933:131) write that the long tail of _Z. trinotatus_ is used as a balancing organ when the mouse is in motion. A tailless mouse, attempting to escape, turned somersaults in the air and invariably landed on its back; the loss of its tail seemed to leave the mouse without compensation for the vigorous push of the hind legs. Dalquest (1948:371) noted that the jumping mouse sometimes walks on all fours, but ordinarily moves by means of short hops on the hind feet alone. When startled, jumping mice travel in bounds of six feet or more at a jump.

_Zapus trinotatus_, according to Bailey (1936:232) and Elliot (1899:261), is mainly nocturnal but occasionally is active in daylight.

Svihla and Svihla (_op. cit._:132) heard captive animals make squeaking noises when fighting. On several occasions captive animals made a drumming noise by rapidly beating the tail against a resonant body such as the bottom of a tin can.

Concerning hibernation, Bailey (_loc. cit._) remarks that animals of this species in Oregon, become fat in early autumn and lay down excess adipose tissue under the skin, over the muscles, and in the abdominal cavity. Svihla and Svihla (_op. cit._:133) noted that captives from the Olympic Peninsula, Washington, gained weight in September and October and became extremely fat. With the additional weight they were more listless and drowsy, often spending days curled up in the hibernating position with the head between the hind legs and the long tail curled completely over the head and body. Warmth aroused the animals to activity, but when the temperature dropped they again hibernated. Flahaut (1939:17) reported the discovery on February 23, 1939, at Henderson Inlet, South Bay, Thurston County, Washington, of two nest cavities inhabited by jumping mice that were hibernating. The nests, four inches apart and 30 inches below the surface of the ground, were approximately five inches in diameter and made of shredded paper. Both mice were dormant, covered by nesting materials and curled up in the aforementioned hibernating posture. Dalquest (1948: 371) writes that in the lowlands of Washington this species disappears by late July but that in the mountains it remains active until the middle of September. Edson (1932:56) records an individual taken on April 20 from its place of hibernation beneath the roots of a decaying stump. This animal quickly roused in the warm mid-afternoon sun but became dormant again when the temperature dropped to 45° F. It seems that animals near the end of hibernation become active on warm days and return to the torpid state on cold ones.

_Enemies._--Little is recorded concerning enemies of _Z. trinotatus_, but Bailey (1936:233) lists owls and other nocturnal birds, weasels, skunks, and badgers as preying on this mouse. Smith and Hopkins (1937:191) found _Z. t. orarius_ in barn owl pellets obtained in Elk Valley, Marin County, California.

_Food._--Bailey (_loc. cit._) remarks that in Oregon, these mice feed mainly on small seeds of grasses, small grains (wheat, barley, oats, and rye), and other plants. These seeds are obtained by cutting the stems, drawing the stems down and biting off lower sections until the seed-laden heads are reached. Bailey (_op. cit._:234) found that _trinotatus_ utilized also the seeds of the western skunk cabbage.

Near Seattle, Washington, according to Dalquest (_loc. cit._), the principal food of _Z. trinotatus_ was velvet grass (_Holchus lanatus_), broad-leaved dock, and the seeds of other grasses. Dalquest reports also that the fruit of the blackberry (_Rubus macropelatus_) is eaten and that an occasional jumping mouse has its chin stained a deep purple by juice from these berries.

_Reproduction._--There is normally a single litter of from four to eight young per year according to Bailey (_loc. cit._). Newly born young have been described by Svihla and Svihla (1933:132) as follows: slightly smaller than newly born harvest mice (_Reithrodontomys m. megalotis_), average weight .8 grams, hairless (without even vibrissae visible), pink, eyes closed, ears folded, heads short and stubby, tails long (longer than those of newly born _Peromyscus_), and bodies surprisingly small (when compared with newly born _Peromyscus maniculatus_).

=Zapus trinotatus eureka= A. B. Howell

_Zapus trinotatus eureka_ A. B. Howell, Univ. California Publ., Zool. 21:229, May 20, 1920.

_Zapus trinotatus trinotatus_, Preble, N. Amer. Fauna, 15:26, August 8, 1899 (part--the part from Crescent City and Carsons Camp, Mad River, California).

_Zapus orarius_ Preble, N. Amer. Fauna, 15:29, August 8, 1899 (part--the part from Eureka and Carsons Camp, Mad River, California).

_Type._--Female, adult, skin and skull, No. 11703, Mus. Vert. Zool.; Fair Oaks, Humboldt County, California; obtained on August 27, 1910, by Joseph S. Dixon, original No. 1743.

_Range._--Northwestern coastal region of California, from Russian Gulch State Park, Mendocino County north to Trinidad, Humboldt County. Zonal range: humid Transition.

_Description._--Size medium; color dull; back near Ochraceous-Buff with heavy admixture of black hairs, forming broad dorsal band; sides from near Ochraceous-Buff to near Ochraceous-Salmon, sometimes with heavy admixture of black hairs; lateral line usually distinct, sometimes blending with color of belly and side; ventral surface usually suffused with color of sides; tail bicolored, dark brown above, white to yellowish-white below; feet grayish-white above; ears dark, edged with color of sides; auditory bullae large; pterygoid fossae broad; incisive foramina relatively short; palatal bridge short; maxillary tooth-rows relatively short; narrow across zygomata; braincase narrow; interorbital region narrow; zygomatic arch relatively short.

_Comparisons._--From _Zapus trinotatus trinotatus_, _Z. t. eureka_ differs in: Size smaller; ventral surface with much greater suffusion of ochraceous; auditory bullae larger; pterygoid fossae relatively broader; frontal region less inflated; palatal bridge shorter; braincase narrower; narrow across zygomata; upper tooth-rows shorter.

For comparison with _Zapus trinotatus orarius_ see account of that subspecies.

_Remarks._--Howell (1920:230), without having examined the material, provisionally referred specimens from Requa and Crescent City, Del Norte County, California, to _Z. t. eureka_. I have studied this material and find the specimens to be intermediate between _Z. t. trinotatus_ and _Z. t. eureka_ in cranial characters (zygomatic breadth, interorbital width, and breadth of braincase), but nearer _Z. t. trinotatus_ in coloration (absence of ochraceous suffusion ventrally). They are here referred to _Z. t. trinotatus_. The zone of intergradation between _Z. t. trinotatus_ and _Z. t. eureka_ seems to extend from Requa, California, north to Gold Beach, Oregon, where other specimens intermediate between these two subspecies, have been obtained. These individuals are also referred to _Z. t. trinotatus_ on the basis of cranial features and color.

_Specimens examined._--Total, 42, all from California, distributed as follows: _Humboldt Co._: Trinidad, 4 (SDM); Carsons Camp, Mad River, 3 (USBS); 3 mi. W Arcata, 5 (MVZ); _7-3/10 mi. E Bayside_, 1 (MVZ); _12 mi. S Korbel, on Maple Creek_, 2 (MVZ); _Falk_, 1 (MVZ); Carlotta, 1 (MVZ); _F. B. Summer Redwoods, S Eureka_, 1 (MVZ); _Maple Creek, 1 mi. W junction Mad River_, 12 (MVZ). _Mendocino County_: Mendocino City, 1 (MVZ); Albion River, 1/3 mi. E MacDonalds Ranch, 1 (MVZ); Russian Gulch State Park, 10 (MVZ).

_Marginal records._--California: Trinidad; Russian Gulch State Park; Albion River, 1/3 mi. E MacDonalds Ranch; Mendocino City; Carlotta.

=Zapus trinotatus montanus= Merriam

_Zapus trinotatus montanus_ Merriam, Proc. Biol. Soc. Washington, 11:104, April 26, 1897; Bailey, N. Amer. Fauna, 55:234, August 29, 1936.

_Zapus montanus_, Preble, N. Amer. Fauna, 15:28, August 8, 1899.

_Type._--Female, adult, skin and skull; No. 79863, U. S. Nat. Mus., Biol. Surv. Coll.; Crater Lake, Klamath County, Oregon; obtained on August 19, 1896, by Edward A. Preble, original No. 1388.

_Range._--From Crater Lake, Klamath County, Oregon, northward along the Cascade Range into Hood River County, Oregon. Zonal range: Transition and Canadian.

_Description._--Size medium; back near Ochraceous-Buff with admixture of black hair, resulting in a grizzled, broad, dorsal band; sides lighter than back, from near Ochraceous-Buff to near Pinkish-Cinnamon, and lined with black hair; lateral line distinct; underparts usually pure white, sometimes with slight suffusion of ochraceous on lower throat and upper chest; tail bicolored, brown above and yellowish-white below; ears dark, sometimes flecked with ochraceous, edged with yellowish-white; feet grayish-white above; braincase relatively narrow; zygomata relatively short; condylobasal length short; mastoid region relatively narrow; palatal bridge short; auditory bullae large; frontal region inflated; pterygoid fossae relatively narrow.

_Comparison._--From _Zapus trinotatus trinotatus_, _Z. t. montanus_ differs as follows: Size averaging smaller; sides more ochraceous, fewer black hairs; upper parts duller; skull smaller; zygomatic arch shorter, braincase relatively narrower; frontal region more inflated; pterygoid fossae relatively narrower; zygomata narrower.

_Remarks._--The systematic status of _Z. t. montanus_ has been in doubt. Several workers, for example, Howell (1920:227) and Preble (1899:28), considered it to be a species, and others (Merriam, 1897a:104, Bailey, 1936:234) considered it to be a subspecies of _Z. trinotatus_. _Z. montanus_ is here considered to be a subspecies of _Z. trinotatus_, because of the agreement of the two in size and shape of the baculum, diameter and pigment pattern of the hair, and the over-all proportions of the skull. In addition, animals from intermediate geographic areas are available and show actual intergradation.

Intergradation has been noted in specimens from North Santiam River, 3400 ft., Oregon. In color, in length of incisive foramina, in breadth of braincase, and in width of zygomata these specimens are intermediate between _Zapus trinotatus montanus_ and _Z. t. trinotatus_, but in the sum-total of characters they are referable to the former. Specimens from Lost Creek R. S., 10 mi. SE McKenzie Bridge, are intermediate in color between _Z. t. trinotatus_ and _Z. t. montanus_; they are referable to _Z. t. montanus_. The animals available from Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood and the one from Mt. Hood, in color, in length of incisive foramina, and in mastoid width, closely approach _Z. t. trinotatus_ from Skamania County, Washington, but in the sum-total of characters are nearest _Z. t. montanus_ and are here referred to _montanus_.

_Specimens examined._--Total, 35, all from Oregon, distributed as follows: _Deschutes County_: Tumalo Creek, 15 mi. W Bend, 6100 ft., 3 (MVZ). _Douglas Co._: Diamond Lake, 1 (USBS). _Hood River Co._: Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood, 10 (MVZ); _Mt. Hood_, 1 (USBS). _Klamath Co._: _Crater Lake_, 3 (MVZ); _1/2 mi. N Government Camp, 6700 ft., Munson Valley, Crater Lake Nat'l Park_, 2 (MVZ); east slope Cascade Divide, 6400 ft., Crater Lake Nat'l Park, 2; Anna Creek, Mt. Mazama, 6000 ft., 2 (USBS). _Lane Co._: Lost Creek R. S., 10 mi. SE McKenzie Bridge, 6 (USBS); _Three Sisters, Alder Springs, 4300 ft._, 2 (USBS). _Linn County_: North Santiam River, 3400 ft., 3 (MVZ).

_Marginal records._--Oregon: Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood; Tumalo Creek, 15 mi. W Bend, 6100 ft.; Anna Creek, Mt. Mazama, 6000 ft.; east slope Cascade Divide, 6400 ft., Crater Lake Nat'l Park; Diamond Lake; North Santiam River, 3400 ft.

=Zapus trinotatus orarius= Preble

_Zapus orarius_ Preble, N. Amer. Fauna, 15:29, August 8, 1899.

_Zapus pacificus_ Merriam, Proc. Biol. Soc. Washington, 11:104, April 26, 1897 (part--the part from Point Reyes, Marin County, California).

_Zapus trinotatus orarius_, Hooper, Miscl. Publ. Mus. Zool. Univ. Michigan, 59:67, January 12, 1944.

_Type._--Male, adult, skin and skull, No. 250, collection of E. A. and O. Bangs (now in Mus. Comp. Zool.); Point Reyes, Marin County, California; obtained on May 14, 1893, by C. A. Allen, original No. 618.

_Range._--Southern and western Marin County, California. Zonal range: Upper Sonoran areas that are moist yet safe from continuous inundation.

_Description._--Size small; back dark ochraceous, usually overlaid with black hairs forming broad dorsal band; side lighter than back with admixture of black hairs; lateral line distinct, usually bright, near Ochraceous-Buff; under parts strongly suffused with ochraceous; tail bicolored, white to yellowish-white below and dark brown above; feet grayish-white above; ears dark, edged with yellowish-white or tan; skull small; zygomata narrow; braincase narrow; maxillary tooth-rows short; interorbital region narrow; incisive foramina short; palatal bridge relatively long; mastoid region relatively broad; occipitonasal length short.

_Comparison._--From _Zapus trinotatus eureka_, _Z. t. orarius_ differs in: Size smaller; color, dorsally and laterally, brighter, more ochraceous; skull averaging smaller in all measurements taken except length of palatal bridge, where it averages longer; auditory bullae smaller, less inflated; pterygoid fossae narrower.

_Remarks._--Preble (1899:30) named this jumping mouse as a full species. Included in the specimens examined were animals from Eureka and Mad River, Humboldt County, California. Howell (1920:231) retained _Z. orarius_ as a full species but restricted its range to Marin County, California, and referred material from northern California, including the animals from Eureka and Mad River, to a new subspecies (_eureka_) of the species _Z. trinotatus_. Howell (_loc. cit._) suggested that _Z. orarius_ had its closest affinity with _Z. t. eureka_ but remarked that intergrading material was not available. Hooper (1944:68) arranged _Z. orarius_ as a subspecies of _Z. trinotatus_ and suggested that intergrades could be expected from geographically intermediate areas, for example, northern Sonoma County, California.

Although animals from intermediate geographic areas still are not available to show actual intergradation, I concur with Hooper (_loc. cit._) and arrange _Z. orarius_ as a subspecies of _Z. trinotatus_. The close relationship of _Z. orarius_ to _Z. trinotatus_ is evident; certain diagnostic characters, held in common, are the shape and size of the os penis, the diameter and pigment pattern of the hair, and the general configuration of the skull.

Interbreeding in the wild between _Z. t. orarius_ and _Z. t. eureka_ probably does not take place, because these subspecies are separated by terrain unsuited to jumping mice.

_Specimens examined._--Total, 29, all from California, distributed as follows: _Marin County_ (MVZ): 3 mi. W Inverness, 300 ft., 14; _5 mi. NNE Point Reyes Lighthouse_, 12; _W end Elk Valley, 10 ft._, 1; West Portal, Fort Barry, 2.

_Marginal records._--California: 3 mi. W Inverness, 300 ft.; West Portal, Fort Barry.

=Zapus trinotatus trinotatus= Rhoads

_Zapus trinotatus Rhoads_, Proc. Acad. Nat. Sci. Philadelphia, 1894:42, January 15, 1895.

_Jaculus hudsonius_, Baird, Repts. Expl. and Surv. 111, 8 (pt. 1): 433, July 14, 1858 (part--the part from Washington).

_Zapus hudsonius_, Coues, Bull. U. S. Geol. and Geog. Surv. of the Territories, 2nd ser., No. 5:260, 1877 (part--the part from Steilacoom [Pierce County], Washington).

_Zapus imperator_ Elliot, Field Columbian Mus., publ. 30, zool. ser., 1:228, February 1, 1899, type from Siegs Ranch, Elwah River, Clallam County, Washington.

_Zapus princeps trinotatus_, Dalquest, Univ. Kansas Publ. Mus. Nat. Hist., 2:371, April 9, 1948.

_Type._--Male, adult, skin and skull, No. 360, S. N. Rhoads Coll.; Lulu Island, mouth of Frazer River, British Columbia; obtained on May 31, 1892, by S. N. Rhoads (type in Philadelphia Acad. Nat. Sci.).

_Range._--Pacific coastal region from Requa, Del Norte County, California, north in Oregon west of the Cascades, and in Washington including the Cascades; to southwestern British Columbia.

_Description._--Size large; back from near Ochraceous-Buff to near Tawny with admixture of black hair forming broad dorsal band; sides lighter than back from near Ochraceous-Buff to near Tawny; lateral line usually distinct; belly white, sometimes with faint suffusion of ochraceous on lower throat and upper chest; tail bicolored, brown above, white to yellowish-white below; ears dark, sometimes flecked with color of sides, edged with ochraceous; feet grayish-white above; palatal bridge relatively short; incisive foramina relatively long; condylobasal region long; zygomatic width great; braincase relatively broad; distance from incisors to postpalatal notch relatively great.

_Comparisons._--For comparisons with _Zapus trinotatus montanus_ and _Zapus trinotatus eureka_ see accounts of those subspecies.

_Remarks._--This subspecies retains most of its diagnostic characters throughout nearly all parts of its geographic range. Intergradation occurs between _Z. t. eureka_ and _Z. t. trinotatus_ in extreme southwestern Oregon and northwestern California (see account of _Z. t. eureka_). Intergrades between _Z. t. montanus_ and _Z. t. trinotatus_ have been commented on in the account of _Z. t. montanus_. Specimens from Eugene, Oregon, according to Bailey (1936:232), show affinity to _Z. t. montanus_ but are considered by him to be _Z. t. trinotatus_.

_Specimens examined._--Total, 238, distributed as follows:

BRITISH COLUMBIA: Alta Lake, on Pac. Gt. Eastern Ry., 2600 ft., 5 (MVZ); Okanagan, 1 (FM); _Vedder Crossing_, 4 (1 MVZ, 3 PM); _Chilliwack Valley_, 2 (NMC); 18 mi. S Chilliwack, 1 (MVZ); Cultus Lake, 2 (NMC); _Lihumption Park, 4500-4800 ft._, 12 (NMC); _Seymour Mtn., 4000 ft._, 8 (1 MVZ, 7 PM); _Cariboo_, 2 (FM); _Sumas_, 8 (1 MVZ, 7 FM); Huntingdon, 40 (NMC); _Parnassus Creek, Black Tusk Meadow, 5200 ft._, 1 (PM); _Howe Sound, Brackendale_, 2 (NMC); Stanley Park, Vancouver, 1 (PM); _Allison Pass, Manning Park_, 1 (PM); Manning Park, 2 (PM).

CALIFORNIA: _Del Norte Co._: Crescent City, 11 (6 FM, 5 USBS); Requa, 4 (FM).

OREGON: _Benton County_: _3 mi. N Corvallis_, 2. _Clatsop County_: Old Fort Clatsop, 100 ft., 11 (MVZ); 7-1/2 mi. S Cannon Beach, 50 ft., 1 (MVZ). _Columbia County_: 7 mi. SE Rainier, 100 ft., 11 (MVZ). _Curry County_: Gold Beach, 3 (FM). _Douglas County_: Gardiner, 7 (5 MVZ, 2 FM). _Lane County_: Sutton Lake, 6 mi. N Florence, 1 (MVZ). _Lincoln County_: _Delake_, 3 (2 MVZ); Newport, 2 (MVZ). _Multnomah County_: Portland, Council Crest, 950 ft., 1 (MVZ). _Tillamook Co._: _Tillamook_, 1 (MVZ); _9 mi. S Tillamook_, 1 (MVZ); Netarts, 3 (SDM); Blaine, 3 (MVZ). _Washington County_: 18-1/2 mi. NW Portland, 1300 ft., 5 (MVZ).

WASHINGTON: _Clallam County_: Deer Lake, 3800 ft., 3. _Clarke County_: _3-1/2 mi. E and 1-1/2 N Amboy, 3500 ft._, 3 (MVZ); _1-1/2 mi. ENE Amboy, 3500 ft._, 13 (MVZ); 3-1/2 mi. E and 5 mi. N Yacolt, 500 ft., 1 (MVZ); _1-1/2 mi. W Yacolt, 800 ft._, 11 (MVZ). _Cowlitz County_: _6 mi. NE Kelso_, 4 (MVZ); _4 mi. E mouth Kalama River_, 5 (MVZ). _King County_: Lakeridge Tract, S end Forest Ave., Lake Washington, 2 (MVZ); Seattle 2 (MVZ); Snoqualmie Pass, 5 (MVZ). _Mason County_: Potlatch, 2 (MVZ). _Pacific County_: _1-1/2 mi. N Chinook, 10 ft._, 1 (MVZ); 3-1/2 mi. SE Chinook, 10 ft., 5 (MVZ). _Pierce Co._: 5 mi. E Tacoma, 4 (MVZ); Puyallup, 3 (1 MVZ, 2 FM); Mt. Rainier, 1 (MVZ); 3 mi. E Ashford, 1 (LMH). _Skamania County_: Ice Caves, 2800 ft., 5 mi. WSW Guler, 1 (MVZ). _Thurston County_: Boston Harbor, 5 (CAS). _Wahkiakum County_: 4 mi. E Skamokawa, 5 (MVZ). _Whatcom County_: Baker Lake, 2 (MVZ).

_Marginal records._--British Columbia: Okanagan; Manning Park. Washington: Baker Lake; Snoqualmie Pass; Mt. Rainier; Ice Caves, 2800 ft., 5 mi. WSW Gulch. Oregon: Portland, Council Crest, 950 ft. California: Requa; Crescent City. Oregon: Gold Beach; Gardiner; Sutton Lake, 6 mi. N Florence; Newport; Netarts; Old Fort Clatsop, 100 ft. Washington: 3-1/2 mi. SE Chinook, 10 ft.; Deer Lake, 3800 ft. British Columbia: Stanley Park, Vancouver; Alta Lake, 2600 ft.

=Zapus princeps= Allen

(Synonymy under subspecies)

_Range._--The Rocky Mountains region from Yukon south into Arizona and New Mexico; westward through eastern Oregon and through the Cascades and Sierra Nevada of California; eastward in the northern Great Plains to extreme eastern parts of the Dakotas (see fig. 46).

_Characters of the species_: _External._--Size medium to large (total length 216 mm to 247 mm); tail longer than head and body (129 mm to 148 mm) and bicolored, pale brown to grayish-brown above, white to yellowish-white below; hind feet long (31 mm to 34 mm), grayish-white above; back variable from yellowish-gray to salmon-brown and ochraceous; sides paler than back; lateral line usually present but sometimes indistinct or entirely absent (when present usually clear Ochraceous-Buff); ventral coloration white, usually suffused with ochraceous; ears usually dark, sometimes flecked and usually narrowly edged with light color; guard hairs average 142 microns (130u to 168u) in diameter; underhair with medullary pigment in form of hollow squares; cuticular scales of underhair larger and fewer than in other species.

_Baculum._--Size medium (total length 5.6 mm to 6.6 mm); base moderately broad (0.7 mm to 0.8 mm); tip narrow (0.26 mm to 0.31 mm) rounded and dished out in dorsal aspect, blunted; shaft rounded, slightly sinusoidal, recurved at tip.

_Skull._--Large, not exceptionally broad and deep in relation to length; rostrum broad but tapering; pterygoid fossa moderately narrow; anterior ramus of zygomatic process usually broad; incisive foramina usually broadly rounded and elongate; auditory bullae usually moderately inflated; coronoid process of mandible relatively short. Upper premolars of medium size (averaging .55 mm in length and .50 mm in breadth), sometimes functional, with occlusal surface normally divided by single shallow re-entrant fold; m1 relatively short, narrow anteriorly.

GEOGRAPHIC VARIATION

There are 11 subspecies recognized, most of which are in the mountains of the western United States and southwestern Canada. There is geographic variation in color, relative proportions of external parts (tail, hind feet, head, and body), and shape and size of the skull.

Three basic types of coloration occur in _Z. princeps_, as pointed out by Hall (1931:9). Yellow-sided dark-backed jumping mice exemplified by _kootenayensis_, _idahoensis_, and _utahensis_ are found to the eastward in the Rocky Mountains. Reddishbrown-sided, brown-backed jumping mice typified by _luteus_ and _pacificus_ are found to the westward in the Sierra Nevada and in New Mexico and Arizona; mice with yellowish-buff or pinkish-buff-sides and light backs are the subspecies, _cinereus_, _curtatus_, and _oregonus_, that occur in the intervening Great Basin.

External dimension as a whole decreases from north to south, although not uniformly. For example, the smallest individuals are of the southernmost geographic subspecies (_Z. p. luteus_), but the largest are of the subspecies (_Z. p. utahensis_) that is near the geographic center of the range for the species. In the skull there is geographic variation in the length and shape of the zygomata, size and shape of the incisive foramina, alignment of maxillary tooth-rows, size and shape of auditory bullae, position of the postpalatal notch in relation to M3, and the presence or absence and size of the medial projection on the inferior ramus of the zygomatic process of the maxillary.

NATURAL HISTORY

_Habitat._--_Zapus princeps_ occurs most commonly adjacent to streams where grasses and herbs are in lush growth. It frequents mountain meadows neighboring small streams and is often taken from alder, aspen, or stands of willow, where the moist ground supports a heavy undergrowth of herbs. Davis (1939:330) found these mice in heavy herbage along a small stream bordered by quaking aspen near Victor, Teton County, Idaho. They were found along streams bordered by willow, rose, alder, huckleberry, sedges, and herbs of various kinds at Alturas Lake, Mill Creek, and at the head of the Pahsimeroi River. Linsdale (1938:195) found jumping mice in the Toyabe Mountains, Nevada, near the streamsides or in seepy areas close to the streams where associated vegetation included rose, willow, wild peach, sage, grasses, and herbs. In the Uinta Mountains, Utah, R. D. Svihla (1931:264) obtained them from willows along streams in mountain parks. Borell and Ellis (1934:37) in the Ruby Mountains, Nevada, found jumping mice to be common in heavy vegetation along streams. Louise Kellogg (1916:369) obtained jumping mice in northern California; all were near water, in grassy meadows, or under alders where vegetation was dense.

_Zapus princeps_ is locally abundant, but its numbers seem to vary considerably from year to year as well as seasonally. Early autumn, when young of the year are abroad, seems to be the period of greatest abundance. Moore (1928:154) remarks that runways were plainly marked and well strewn with four-inch pieces of brome-grass. Davis (1939:334) notes that _Z. princeps_ has runways, and found that sections, four inches long, of cut grass piled in runways was good evidence of the presence of the mouse.

_Behavior._--In reference to locomotion of _Z. princeps_, Davis (_loc. cit._) writes, "In rapid progression jumping mice move by a series of zigzag hops. One young of the year found in tall grass near Victor made horizontal leaps of approximately three feet. The zigzag course was difficult for me to follow, and I was led to wonder if this mode of locomotion were not advantageous to the mice in eluding animals that would do them harm." Hollister (1912:26) remarked that _princeps_, when startled, sometimes jumps five to six feet at a bound. Concerning the swimming ability of _Z. princeps_, Bailey (1936:233) quotes from Hollister's notes, "While I was walking around the grassy border of a small pond one jumped out at my feet and struck in the water like a frog, which at first it was thought to be, until it was seen swimming across the pond on the surface of the water ... he certainly handled himself as if perfectly at home and swam with little effort and great speed over the still surface of the pond." Davis (1939:334) obtained two individuals at Mill Creek, Idaho, in traps placed on artificial islands of stones in the middle of the creek where the water was about six inches deep. He speculated that the only way the mice could have reached the traps was by swimming. Grinnell, Dixon, and Linsdale (1930:531) record an individual which was seen hopping in the inch-deep water of a small stream at Lake Helen, California.

According to Hollister (1912:26) and Davis (1939:335), jumping mice are for the most part nocturnal, but occasionally they are seen by day in tall grass.

Little is recorded concerning the hibernation of _Z. princeps_. What data are available suggest that, starting in July, these animals accumulate a heavy layer of fat on the inside of the skin with especially large amounts in the inguinal region. By August or early September, animals are excessively fat, and the start of hibernation is dependent then upon the arrival of a heavy cold snap. Grinnell, Dixon, and Linsdale (1930:531), in their study of the vertebrates of the Lassen Peak region of California noted that the latest activity by these mice was September 13. As regards the time of onset of hibernation in Idaho, Davis (1939:336) states that, "I know of no records of capture later than September and infer that hibernation begins in that month or the next." Bailey (1932:227) writes that in New Mexico, animals obtained on September 20 were very fat, probably were ready to hibernate at the first cold wave, and had winter nests in burrows well underground.

_Enemies._--Bailey (_loc. cit._) lists hawks, owls, and weasels as natural predators on _Z. princeps_. Stanford (1931:362) records the garter snake (_Thamnophis_) as a predator of jumping mice. A large snake of this genus obtained by him regurgitated two jumping mice a few hours after its capture. Grinnell, Dixon, and Linsdale (1937:232) report that on Parker Creek, in California, H. C. Bryant frightened a weasel that dropped a freshly killed jumping mouse. Crowe (1943:407) reported _Cuterebra_ fly larvae in the inguinal region of a _Z. princeps_ obtained at Invermere, British Columbia. Several mice of this species taken at Moccasin Lake, 19 mi. W and 4 mi. N of Lander, 10,000 ft., Fremont County, Wyoming, were heavily infested with mites of the family Laelaptidae.

_Food._--In early September in central Utah, Moore (1928:154) found only a white, starchy, glutinous paste in stomachs of six _Z. princeps_ and only traces of a brown seed coat in a seventh. The main seeds eaten seemed to be from an introduced brome-grass which was abundant in the vicinity of capture. Bailey (1932:226) wrote of _Z. princeps_ in New Mexico, that "In feeding they cut down the tall grass, beginning at the bottom and cutting the stem at intervals as high as they can reach until the seed part of the grass is brought down." He (_op. cit._:227) remarked that the food was almost entirely seeds of grass and grasslike plants and that the stomach contents almost always were perfectly clean white dough from the shelled kernels of small seeds.

_Reproduction._--Females with embryos have been collected from late May to mid-July and lactating individuals until late August. Possibly there is only one litter per season as Davis (1939:336) suggests is the case in Idaho.

Embryos in 25 pregnant females averaged 5 (2-7). The mammae of the female are arranged in four pairs (two abdominal, one pectoral, and one inguinal).

_Z. princeps_ builds a grass nest on the ground which is placed under cover of vegetation or surface litter. Bailey (1932:227) writes that in New Mexico jumping mice of this species use fibers of grass to construct a ball-shaped nest. The nest usually has one opening but sometimes there are two. In the Ruby Mountains, of Nevada, Borell and Ellis (1934:37) found the globular nests of this mouse on the ground in tall grass.

=Zapus princeps cinereus= Hall

_Zapus princeps cinereus_ Hall, Univ. California Publ. Zool., 37:7, April 10, 1931.

_Type._--Female, adult, skin and skull; No. 45422, Mus. Vert. Zool.; Pine Canyon, 6600 feet altitude, Raft River Mountains, 17 mi. northwest Kelton, Boxelder County, Utah; obtained on July 14, 1930, by Annie M. Alexander; original No. 689.

_Range._--Raft River Mt's in northwestern Utah and in isolated mountains in southern Idaho. See fig. 46. Zonal range: Transition and Canadian.

_Description._--Size, medium; back with broad mid-dorsal band, varying from pale brown mixed with Pinkish-Buff to dark brown mixed with Warm Buff or Ochraceous-Buff; sides varying from near Pinkish-Buff to near Ochraceous-Buff; ventral surface white to base of hairs, not suffused with other color; tail bicolored, pale brown above and white to yellowish-white below; ears dark, edged with white or yellowish-white; upper teeth divergent anteriorly; auditory bullae small; skull relatively long; zygomata relatively weak and not widely bowed; nasals wide posteriorly; pterygoid fossae relatively narrow.

_Comparisons._--From _Zapus princeps nevadensis_, _Z. p. cinereus_ differs as follows: Size averaging smaller; entire coloration lighter; zygomata not so widely bowed; incisive foramina not so wide posteriorly; auditory bullae smaller; nasals wider posteriorly; pterygoid fossae narrower.

From _Zapus princeps idahoensis_, _Z. p. cinereus_ can be distinguished by: generally paler color; smaller auditory bullae; broader interorbital region; anteriorly diverging tooth-rows; narrower pterygoid fossae.

For comparison with _Zapus princeps utahensis_ see account of that subspecies.

_Remarks._--Davis (1939:343) writes that "since _cinereus_ was described from nine specimens, only two of which are near adult, one cannot place much value on the coloration ascribed to it by Hall (1931:7)." I examined the type series and found, as did Davis (_loc. cit._), that the type is much lighter and grayer than is a near adult paratype, which was obtained the same day; however, I do not concur with Davis (_loc. cit._) that specimens from Mt. Harrison, 10 mi. S Albion, Idaho, which are darker and much more ochraceous than the paratype, necessarily are more nearly typically colored. These individuals, judged by cranial characters, are more nearly typical of _cinereus_ but show intergradation with _Z. p. idahoensis_ in their darker and more ochraceous pelage.

Durrant (1952:387) found that the gray color of _Z. p. cinereus_ was not diagnostic in separating _Z. p. cinereus_ from _Z. p. utahensis_, because gray animals are also found in _Z. p. utahensis_. Specimens from Camp Tendoy, Pocatello, Idaho, are intermediate in color and in cranial characters as between _Z. p. idahoensis_ and _Z. p. cinereus_, but here are referred to _Z. p. cinereus_. Whitlow and Hall (1933:268) compared these individuals with specimens of _Z. p. princeps_ and _Z. p. cinereus_, finding them intermediate but in the aggregate of several differential characters better referred to the latter.

_Specimens examined._--Total, 35, distributed as follows:

IDAHO: _Bannock County_: Camp Tendoy, Pocatello, 2 (MVZ). _Cassia County_: Mt. Harrison, 10 mi. S Albion, 16 (MVZ).

UTAH: _Boxelder Co._: _south fork of George Creek, 5 mi. SE Yost, Raft River Mts., 6700 ft._, 1 (UU); _George Creek, 7 mi. SE Yost, Raft River Mts., 6500 ft._, 6 (UU); _Pine Canyon, 6600 ft., 17 mi. NW Kelton, Raft River Mts._, 8 (MVZ); Pine Creek, 3 mi. N Rosette, Raft River Mts., 6100 ft., 2 (UU).

_Marginal records._--Idaho: Camp Tendoy, Pocatello. Utah: Pine Creek, 3 mi. N Rosette, Raft River Mts., 6100 ft. Idaho: Mt. Harrison, 10 mi. S Albion.

=Zapus princeps curtatus= Hall

_Zapus princeps curtatus_ Hall, Univ. California Publ. Zool., 37:7, April 10, 1931.

_Zapus princeps oregonus_, Taylor, Univ. California Publ. Zool., 7:281, June 24, 1911.

_Type._--Female, adult, skin and skull, No. 7991, Mus. Vert. Zool.; head of Big Creek, 8000 feet altitude, Pine Forest Mountains, Humboldt County, Nevada; obtained on June 30, 1909, by Walter P. Taylor and C. H. Richardson, original No. 777 of W. P. T.

_Range._--Pine Forest Mt's, Humboldt County, Nevada. See fig. 46. Zonal range: Transition and Canadian.

_Description._--Size medium; back pale near Light Ochraceous-Buff with admixture of black hair forming dark dorsal band; sides lighter than back; lateral line faintly indicated; ventral surface white; tail bicolored, grayish-white to yellowish-white below and pale brown above; ears dark, edged with yellowish-white; feet grayish-white above; palatal bridge short; tooth-rows almost parallel; mastoid region of skull relatively narrow; incisive foramina wide posteriorly; narrow across zygomata; nasals relatively narrow posteriorly.

_Comparisons._--For comparison with _Zapus princeps oregonus_ see account of that subspecies.

_Remarks._--This jumping mouse, which was described from the Pine Forest Mountains, closely resembles _Zapus princeps oregonus_ but differs in lighter color, slightly smaller body, less divergent tooth-rows, shorter palate, and narrower skull across the mastoid region.

The Pine Forest Mountains are isolated from neighboring boreal regions by a belt of the Upper Sonoran Life-zone, which is inhospitable to _Zapus_; therefore, intergrades between _Z. p. oregonus_ and _Z. p. curtatus_ are not known and probably do not exist. Nevertheless, _Z. p. curtatus_ shows close affinity with _Z. p. oregonus_, as indicated by Taylor (1911:281), and I agree with Hall (1931:7) that the relationships of _Z. p. curtatus_ are best expressed by arranging it as a subspecies of _Zapus princeps_.

_Specimens examined._--Total, 18, all from Nevada, distributed as follows: _Humboldt County_: Pine Forest Mts.; Alder Creek, 6000 ft., 2 (MVZ); head of Big Creek, 8000 ft., 14 (MVZ); _Leonard Creek, 6500 ft._, 2 (MVZ); Meadow, 1 (MVZ).

_Marginal records._--Nevada: Pine Forest Mts., Alder Creek; Meadow.

=Zapus princeps idahoensis= Davis

_Zapus princeps idahoensis_ Davis, Jour. Mamm., 15:221, August 10, 1931.

_Jaculus hudsonius_, Allen, Bull. Essex Inst., 6:61, April, 1874 (part--the part in Carbon County, Wyoming).

_Zapus hudsonius_, Merriam, N. Amer. Fauna, 5:72-73, July 30, 1891.

_Zapus princeps princeps_, Preble, N. Amer. Fauna, 15:22-23, August 8, 1899 (part).

_Type._--Male, adult, skin and skull; No. 54845, Mus. Vert. Zool.; 5 mi. E Warm Lake, 7000 ft., Valley County, Idaho; obtained on July 9, 1932, by Robert T. Orr; original No. 660.

_Range._--From Banff, Alberta, southward through extreme southwestern Alberta and extreme southwestern British Columbia, most of the panhandle of Idaho, Kamiak Butte in eastern Washington, western Montana, and western Wyoming (Green, Wind River and Absoroka ranges of the Rocky Mt's). See fig. 46.

_Description._--Size, medium; back from near Clay Color to near Warm Buff, usually overlaid with black hairs forming broad dorsal band; sides lighter than back; lateral line indistinct or wanting; belly pure white, occasionally faintly tinged with Ochraceous-Buff; tail indistinctly bicolored, tan to grayish-white below and pale brown above; hind feet grayish-white above; ears dark, edged with white or yellowish-white; postpalatal notch anterior to posterior border of last molars; proximal part of inferior ramus of zygomatic process of maxillary relatively narrow and usually without enlarged median projection; auditory bullae well inflated; incisive foramina relatively narrow.

_Comparisons._--From _Zapus princeps kootenayensis_, _Z. p. idahoensis_ differs as follows: Size averaging larger; upper parts with greater suffusion of ochraceous, not grayish or dusty; skull larger; incisive foramina longer and relatively wider; zygomatic breadth averaging greater; nasals broader at tips; auditory bullae more inflated.

From _Zapus princeps oregonus_, _Z. p. idahoensis_ differs in: Size averaging smaller; upper parts generally more suffused with black hairs, on the average more yellowish with less ochraceous; skull smaller; incisive foramina narrower (breadth less, instead of more, than 52 per cent of length); palatal bridge shorter; zygomatic arch shorter; pterygoid fossae narrower.

From _Zapus princeps utahensis_, _Z. p. idahoensis_ can be distinguished by: Size less; color slightly darker; skull averaging smaller in zygomatic breadth, least interorbital constriction, and occipitonasal length; palate narrower; upper tooth-rows nearly parallel as opposed to diverging anteriorly.

From _Zapus princeps minor_, _Z. p. idahoensis_ differs in: Size larger; color of underparts less ochraceous; lateral line indistinct or wanting; skull averaging larger in all measurements taken except that the two subspecies are approximately same in least interorbital constriction, length of zygomatic arch, and distance from anterior face of incisors to postpalatal notch; nasals, in profile, straight instead of with proximal third depressed; postpalatal notch anterior to posterior face of last molar, instead of even with, or usually posterior to, same.

From _Zapus princeps saltator_, _Z. p. idahoensis_ differs as follows: Size averaging slightly larger; color darker, being less ochraceous and more yellow dorsally and laterally; auditory bullae more inflated; zygomatic arches less bowed laterally; incisive foramina narrower.

For comparison with _Zapus princeps princeps_ and _Zapus princeps cinereus_ see accounts of those subspecies.

_Remarks._--Intergradation occurs at almost all of the places where the range of _Z. p. idahoensis_ is known to touch that of any other geographic race. Nevertheless, each of the populations studied has characters which make this subspecies recognizable as a taxonomic unit, although its characters are not yet stabilized even in the central part of its range.

Among named subspecies of _Zapus princeps_, _Zapus p. idahoensis_ most closely resembles _Zapus princeps kootenayensis_, its nearest geographic neighbor to the north. Three specimens from 2 mi. NE Weippe, 3000 ft., Idaho, are best referred to _Z. p. idahoensis_ but show relationship to _Z. p. kootenayensis_ in size and shape of the tympanic bullae. The relationship of individuals from Idaho, here referred to _Z. p. idahoensis_, from Glidden Lakes, Enaville, Cascade Creek, and 13 mi. E and 5 mi. N Coeur d'Alene, is discussed in the account of _Z. p. kootenayensis_. British Columbian specimens from Newgate and Crows Nest Pass, 4450 ft., as well as Albertan specimens from Crows Nest Pass and various places in Waterton Lake Park, resemble _Z. p. kootenayensis_ in color but cranially are more nearly like _Z. p. idahoensis_.

Intergradation with _Zapus princeps oregonus_ was noted by Davis (1939:340) in a specimen from Cedar Mountain in Idaho. I have not seen this individual which he referred to _Z. p. idahoensis_ but have seen a specimen from the N Fork of Potlatch River (15 mi. SE Cedar Mt.), which, in color, closely resembles _Z. p. oregonus_ but cranially (shape of incisive foramina, size, and inflation of auditory bullae) is more nearly like _Z. p. idahoensis_ to which it is referred. Davis (_loc. cit._) indicates that specimens from summit of Smith Mt., from 1 mi. N Bear Creek R. S., from 1/2 mi. E Black Lake, and from 3 mi. W Payette Lake, Idaho, are in an area of intergradation between _Z. p. oregonus_ and _Z. p. idahoensis_, but he referred them to _Z. p. idahoensis_ on the basis of cranial characters and length of hind foot. Seven specimens from Alturas Lake, 7000 ft., Idaho, were likewise so allocated by Davis (_loc. cit._). I concur with him and in addition refer the following intermediate individuals from Idaho to _Z. p. idahoensis_: New Meadow, 1; Warren, 1; Perkins Lake, 7000 ft., Sawtooth Nat'l Forest, 1; Prairie Creek, 12 mi. W Ketchum, 2400 ft., 3. All are more nearly like _Z. p. oregonus_ in color but cranially they show more resemblance to _Z. p. idahoensis_.

In the eastern part of the range of _Z. p. idahoensis_, intergradation occurs with _Zapus princeps minor_, as at 15 mi. S Heath, N Fork Flat Willow Creek, Big Snowy Mt's, Montana. Specimens from there have the lateral line enlarged and the maximum seen in this species of Ochraceous color ventrally. The pterygoid fossae are large and the bullae are reduced as in _Z. p. minor_, but in the sum total of the characters the mice more closely resemble _Z. p. idahoensis_. At Lewistown, 7 mi. NE Judith Mt's, Lime Kiln Gulch, Montana, the animals are colored as are _Z. p. minor_ but cranially are like _Z. p. idahoensis_ to which they are referred. Specimens from the Highwood Mt's, Montana, also are intergrades; they have a relatively distinct lateral line as in _Z. p. minor_ but show no ventral suffusion of Ochraceous; they have large bullae, nasals that are straight in lateral profile and other cranial characters of _Z. p. idahoensis_ to which they are here referred.

A single specimen from Kamiak Butte, Whitman County, Washington, has been referred to _Z. p. idahoensis_ by Dalquest (1948:373). I have not seen this individual, but, on geographic grounds, it is likely to be of this subspecies.

_Specimens examined._--Total, 342, distributed as follows:

ALBERTA: Boom Creek, 5600 ft., 27 mi. W Banff, 2 (NMC); _Banff, Cascade Basin_, 2 (NMC); _Bryant Creek, Banff Park_, 1 (NMC); _Spray River, 7 mi. Cabin, Banff Park_, 3 (NMC); Crows Nest Pass, 2 (NMC); Waterton Lakes Park, 16 (NMC); _Linnets Pond, Waterton Lakes Park_, 4 (NMC); _Bertha Creek, Waterton Lakes Park_, 8 (NMC).

BRITISH COLUMBIA: Vermilion Crossing, Kootenay, 1 (ROM); Paradise Mine, 3 (PM); Crows Nest Pass, 4450 ft., 3 (NMC); Newgate, 10 (NMC).

IDAHO: _Adam Co._: 1/2 mi. E Black Lake, 6800 ft., 8; _summit of Smith Mtn., 7500 ft._, 9 (3 MVZ); 1 mi. N Bear Creek R. S., SW Slope Smith Mtn., 5400 ft., 13; New Meadows, 1 (USBS); _3 mi. W Payette, 5400 ft._, 4 (MVZ). _Blaine County_: _Perkins Lake, 7000 ft., Sawtooth Nat'l Forest_, 1; _Alturas Lake, 7000 ft._, 3 (MVZ); Prairie Creek, 12 mi. NW Ketchum, 2400 ft., 3. _Clearwater County_: 2 mi. NE Weippe, 3000 ft., 3 (MVZ). _Custer County_: Loon Creek R. S., 6000 ft., Challis Nat'l Forest, 2; _Head Pahsimeroi River_, 2 (MVZ); Mill Creek, 14 mi. WSW Challis, 8370 ft., 1 (MVZ). _Fremont County_: 7 mi. W West Yellowstone, 7000 ft., 3; _17 mi. E and 4 mi. N of Ashton, 6275 ft._, 9 (MVZ). _Idaho Co._: Packers Meadow, near state line, South Lobo Hot Springs, 5150 ft., 7 (USBS); _Warren_, 1 (USBS). _Kootenai Co._: 13 mi. E and 5 mi. N Coeur d'Alene, 5; _Cascade Creek, 36 mi. E Coeur d'Alene, Coeur d'Alene Nat'l Forest_, 1 (USBS). _Latah Co._: N Fork Potlatch River, 1 (USBS). _Lemhi County_: Salmon River Mts., 3 (USBS). _Shoshone Co._: Enaville 1 (USBS); _Glidden Lakes, 5700 ft._, 4 (MVZ). _Valley County_: 5 mi. E Warm Lake, 7000 ft., 6 (MVZ); _5 mi. W Cape Horn, 7000 ft., Sawtooth Range_, 1 (MVZ).

MONTANA: _Beaverhead County_: Birch Creek, 18 mi. NE Dillon, 7100 ft., 14 (MVZ). _Carbon Co._: _Pryor Mts._, 1 (USBS); 2 mi. E Shriver, 6500 ft., 6 (MVZ). _Cascade Co._: Neihart, 1 (USBS). _Chouteau Co._: _Upper Muddy_, 1 (USBS); Highwood Mts., 2 (USBS). _Fergus Co._: Lime Kiln Gulch, 7 mi. NE Judith Mts., 3 (USBS); 15 mi. S Heath, N Fork Flat Willow Creek, 8 (USBS); _10 mi. W Tyler, N Fork Flat Willow Creek_, 1 (USBS); _Crystal Lake, 6000 ft., Big Snowy Mts._, 3 (UM). _Flathead Co._: Waterton Lake, 1 (USBS); _Crosley Lake, Glacier Nat'l Park_, 1 (USBS); Paola, 1 (USBS); _Summit_, 2 (USBS); _1 mi. W and 2 mi. S Summit, 5000 ft._, 12. _Gallatin Co._: 4 mi S Logan, Camas Creek, Big Belt Mts., 5 (USBS); Gallatin Gateway, 5 (SDM); west fork West Gallatin River, 6500 ft., 6 (USBS). _Glacier Co._: Babb, 1 (LMH); _2-1/2 mi. W and 1-1/2 mi. S Babb, 4700 ft._, 1; _Many Glaciers, 4900 ft., Glacier Nat'l Park_, 5 (MVZ); _6 mi. S St. Marys, 6500 ft._, 1; _St. Marys Lake_, 7 (USBS); _McDermit Lake_, 1 (USBS); Blackfoot Agency, 1 (USBS). _Golden Valley County_: _Swimming Woman Canyon, 3/4 mi. S Fergus County line, Big Snowy Mts._, 4 (UM). _Judith Basin Co._: _Little Belt Mts., Dry Wolf Creek, 20 mi. SW Stanford_, 4 (USBS); 13 mi. W Buffalo, 1 (USBS). _Madison Co._: 12 mi. SW Alder, Hinch Creek, Ruby Mts., 2 (USBS). _Meagher Co._: _16 mi. N White Sulphur Springs, Little Belt Mts._, 7 (USBS). _Park County_: _West Boulder Creek, 18 mi. SE Livingston_, 1 (USBS); Emigrant Gulch, 3 mi. SE Chico, 6500 ft., 4 (USBS); 2 mi. NE Cooke, 8000 ft., 22 (MVZ). _Ravalli County_: 3 mi. SW Florence, 3700 ft., 1; 6 mi. E Hamilton, 3700 ft., 1. _Sanders Co._: Prospect Creek, near Thompson, 1 (USBS). _Sweet Grass Co._: _near head of Big Timber Creek, 5200 ft., Crazy Mts._, 11 (USBS); Brannin Ranch, Sweet Grass Creek Canyon, 6 (UM); _Big Timber_, 1 (USBS). _Teton County_: 17-1/2 mi. W and 6-1/2 mi. N Agusta, 5100 ft., 2.

WYOMING: _Fremont County_: Moccasin Lake, 19 mi. W and 4 mi. N of Lander, 10,000 ft., 1; 23-1/2 mi. S and 5 mi. W Lander, 8600 ft., 4. _Park County_: 31-1/2 mi. N and 36 mi. W Cody, 6900 ft., 7; _28 mi. N and 30 mi. W Cody, 7200 ft._, 1; _16-1/4 mi. N and 17 mi. W Cody, 5625 ft._, 14; 2 mi. S and 42 mi. W Cody, 6400 ft., 5; 12 mi. W Wapiti, 6 (LMH); _25 mi. S and 28 mi. W Cody, 6350 ft._, 5. _Sublette County_: E end Island Lake, 10,600 ft., 3 mi. S Fremont Park, 1; _N side Halfmoon Lake, 7900 ft._, 3; _W end Halfmoon Lake, 7900 ft._, 2; _10 mi. NE Pinedale, 8000 ft._, 1; _5 mi. E and 8 mi. N Pinedale, 7500 ft._, 1; 3 mi. E and 5 mi. N Pinedale, 7500 ft., 4; 19 mi. W and 2 mi. S Big Piney, 7700 ft., 3.

_Marginal records._--Alberta: Boom Creek, 5600 ft., 27 mi. W Banff; Crows Nest Pass; Waterton Lakes Park. Montana: Highwood Mts.; 15 mi. S Heath, N Fork Flat Willow Creek; 2 mi. E Shriver, 6500 ft. Wyoming: 23-1/2 mi. S and 5-1/2 mi. W Lander, 8600 ft.; 10 mi. W and 2 mi. S Big Piney, 7700 ft. Idaho: 7 mi. W West Yellowstone, 7000 ft.; Prairie Creek, 12 mi. NW Ketchum, 2400 ft.; 5 mi. W Warm Lake, 7000 ft.; 1 mi. N Bear Creek R. S., SW slope Smith Mtn., 5400 ft.; N Fork Potlatch River; 13 mi. E and 5 mi. N Coeur d'Alene. British Columbia: Newgate; Vermilion Crossing, Kootenay.

=Zapus princeps kootenayensis= Anderson

_Zapus princeps kootenayensis_ Anderson, Ann. Rept. Nat. Mus. Canada for 1931:108, November 24, 1932.

_Zapus princeps princeps_, Preble, N. Amer. Fauna, 15:23, August 8, 1899 (part).

_Type._--Adult female, skin and skull, No. 10,020, Nat. Mus. Canada; near summit of Green Mountain, head of Murphy Creek, about 10 miles north of Rossland, West Kootenay district, British Columbia, at about, 6000 ft.; latitude 49° 13' north, longitude 117° 52' west; obtained on July 18, 1929, by R. M. Anderson, original No. 24.

_Range._--From Glacier in the Selkirk Range, British Columbia, south to 5 mi. W Cocolalla, Bonner County, Idaho, west and north to Sullivan Lake, Pend Oreille County, Washington; and northwestward to Manning Park on the eastern summit of the Cascade Range in British Columbia. See fig. 46.

_Description._--Size, medium; color moderately dark; upper parts noticeably dull and dusty; broad dorsal band of dull Ochraceous-Buff to near Warm Buff sprinkled with black hair to a varying degree, resulting in two color phases (dark has more black hair; Ochraceous phase or Warm Buff phase has more brown hair); sides paler than back owing to fewer black hairs; lateral line, when present, narrow and dull; ventral surface pure white; tail bicolored, pale brown above, yellowish-white to dull white below; ears dark with narrow white or yellowish-white edgings; feet white above; skull narrow across zygomata; incisive foramina narrow; bullae moderately inflated; nasals narrow at tips; postpalatal notch anterior to posterior face of last molars; braincase moderately narrow; zygomatic arch short.

_Comparisons._--From _Zapus princeps saltator_, _Z. p. kootenayensis_ differs as follows: Upper parts generally dull with less ochraceous; sides with more yellow, less ochraceous; lateral line wanting or not bright; skull averaging slightly smaller; incisive foramina smaller and narrower posteriorly; small medium projection on inferior ramus of the zygomatic process of maxillary frequently present instead of absent; pterygoid fossae shorter and narrower.

For comparison with _Zapus princeps idahoensis_ see account of that subspecies.

_Remarks._--This subspecies is paler and averages smaller than either of the subspecies with adjoining geographic ranges. There is intergradation with _Zapus princeps idahoensis_ in color, shape and size of incisive foramina, and in the shape of the nasals in Idaho-taken specimens from Glidden Lakes and Enaville. These individuals are thought to be _Z. p. idahoensis_. Specimens from the same state taken at Cascade Creek and 13 mi. E and 5 mi. N Coeur d'Alene show intergradation in color, size and inflation of bullae, configuration of nasals, and shape of the vomer between _Zapus princeps idahoensis_ and _Z. p. kootenayensis_. The majority of characters studied show these animals to be referable to _Z. p. idahoensis_.

Specimens from Monashee Pass, 4000 ft., British Columbia, show relationship to _Zapus princeps saltator_ in the posteriorly wide incisive foramina, in the narrow vomer, and, in some individuals, in the increased amount of ochraceous, dorsally and laterally. The majority of characters studied show these animals to be referable to _Z. p. kootenayensis_.

The animals available from Glacier, British Columbia, are in color more nearly like _Z. p. saltator_ and cranially combine the characters of _Z. p. idahoensis_, _Z. p. saltator_, and _Z. p. kootenayensis_. The sum total of their characters places them with _Z. p. saltator_. Anderson (1932:108) remarks on the disparity of size between the two sexes of _Z. p. kootenayensis_, stating that females are considerably larger than males. I have examined most of the material used in the original description and find that animals of like age in the two sexes show no significant size difference. Anderson (_loc. cit._) seems to have compared young males with adult females.

_Specimens examined._--Total, 68, distributed as follows:

BRITISH COLUMBIA: Manning Park, 3 (PM); _Good Fellow Creek, Manning Park_, 1 (PM); _Mt. Beaver Valley, 6300 ft., Manning Park_, 1 (PM); _Timberline Valley, 6500 ft._, 3 (PM); _Allison Pass, 1 mi. E Manning Park_, 1 (PM); Monashee Pass, 4000 ft., 13 (PM); Hope-Princeton Summit, 5500 ft., 1 (NMC); _Hedley, Stirling Creek_, 1 (NMC); Anarchist Mts., 1 (PM); Fairview-Keremeos Summit, 5 (NMC); _Westbridge_, 2 (NMC); _Midway_, 2 (NMC); Green Mtn., near Rossland, 6000 ft., 12 (11 NMC, 1 MVZ); _Mt. Old Glory, 7000 ft., Rossland_, 5 (4 NMC, 1 MVZ); _Rossland, 5800 ft._, 12 (11 NMC, 1 MVZ); Camp 6, Meadow Creek, 7 mi. SE of Yahk, 1 (NMC).

IDAHO: _Bonner County_: 5 mi. W Cocolalla, 3500 ft., 2 (MVZ). _Boundary County_: 4 mi. W Meadow Creek, 3000 ft., 2 (MVZ).

_Marginal records._--British Columbia: Monashee Pass, 4000 ft.; Camp 6, Meadow Creek, 7 mi. SE Yahk. Idaho: 4 mi. W Meadow Creek, 3000 ft.; 5 mi. W Cocolalla, 3500 ft. British Columbia: Hope-Princeton Summit, 5500 ft.; Manning Park.

=Zapus princeps luteus= Miller

_Zapus luteus_, Miller, Proc. Biol. Soc. Washington, 24:253, December 23, 1911.

_Zapus luteus australis_, Bailey, Proc. Biol. Soc. Washington, 26:132, May 21, 1913. Type from Socorro, Socorro County, New Mexico.

_Type._--Female, adult, skin and skull, No. 133601, U. S. Nat. Mus. Biol. Surv. Coll., Espanola, 5000 ft., Rio Arriba Co., New Mexico; obtained on June 24, 1904, by McClure Surber, original No. 162.

_Range._--White Mt's of southern Apache County and northern Greenlee County, Arizona; in New Mexico, from the Sacramento Mt's, Otero County, northward to the San Juan Mt's, Rio Arriba County. See fig. 46. Zonal range: Lower Sonoran (1 individual), Upper Sonoran, Transition, and Canadian.

_Description._--Size, small; back near Ochraceous-Buff, having black hair interspersed; mid-dorsal band not always well marked; sides Ochraceous-Buff with fine admixture of black hair; lateral line blending with Ochraceous-Buff of sides, not distinct; ventral surface white to base of hairs, in some cases lightly suffused with color of sides; tail indistinctly bicolored, tan to grayish-white below and brown above; hind feet grayish-white above; ears brownish, narrowly edged with Ochraceous-Buff; skull small; antorbital foramina relatively large; interorbital region broad; inferior ramus of the zygomatic process of the maxillary broad, often with medial projection; incisive foramina narrow posteriorly becoming broadly rounded anteriorly; palatal bridge relatively long; pterygoid fossae narrow; zygomatic arches relatively robust; nasals tapering at each end.

_Comparisons._--From _Zapus princeps princeps_, _Z, p. luteus_ differs as follows: Size, smaller; color lighter, more Ochraceous-Buff; ears lighter, edged with Ochraceous-Buff as compared with white or yellowish-white; lateral line indistinct or wanting as opposed to distinct; dorsal stripe not well defined; interorbital region broader; antorbital foramina relatively larger; zygomatic arches more robust; nasals tapering at each end as opposed to parallel sided; auditory bullae smaller, less inflated.

_Remarks._--The characters of this subspecies are relatively stable throughout most of its geographic range. Hall and Davis (1934:56) remarked that their material from the White Mountains of Arizona answered precisely to Miller's original description (1911:253) of the species, and my examination of these and other specimens from that area indicates the same thing except that the specimens average slightly darker mid-dorsally than those from New Mexico.

_Zapus luteus australis_, based on a single individual taken in a riparian thicket along the Rio Grande at Socorro, New Mexico, is referable to _Z. p. luteus_. The diagnostic characters, referred to in the original description, are as follows: Small, slender, and very narrow skull; especially narrow braincase; slender rostrum; and light dentition. These are expressions of age, rather than of geographic variation, in that the individual is a subadult (young of the year). The color, which is paler than in adults of _Z. p. luteus_, is almost identical with that of a subadult (No. 205585 USBS) from Alpine, Arizona. I can see no basis for recognition of _Z. p. australis_ and the name, therefore, is placed as a synonym of _Z. p. luteus_.

Four specimens from 4 mi. NE El Rito, 7000 ft., New Mexico, show intergradation, in the shape of the nasals and incisive foramina, in the robustness of the zygomatic arch, and in the breadth of the braincase with a specimen of _Zapus princeps princeps_ from Tierra Amarilla, New Mexico. In color and in external measurements as well as in other cranial characters they closely agree with typical _Z. p. luteus_ and are here referred to the latter.

_Specimens examined._--Total, 49, distributed as follows:

ARIZONA: _Apache Co._: North Fork White River, White Mts., 24 (SDM); Alpine, 8500 ft., 6 (USBS); West Fork Black River, 7700 ft., 8 (MVZ); _Greenlee County_: Hannagan Creek, 8200 ft., 2 (MVZ).

NEW MEXICO: _Otero Co._: 12 mi. E Cloudcroft, 7500 ft., 2 (USBS). _Rio Arriba Co._: 4 mi. NE of El Rito, 7000 ft., 4; Espanola, 5000 ft., 2 (USBS). _Socorro Co._: Socorro, 1 (USBS).

_Marginal records._--New Mexico: 4 mi. N El Rito, 7000 ft.; Espanola, 5000 ft.; 12 mi. E Cloudcroft, 7500 ft. Arizona: Hannagan Creek, 8200 ft.; W. Fork Black River, 7700 ft.; N. Fork White River, White Mts. New Mexico: Socorro.

=Zapus princeps minor= Preble

_Zapus princeps minor_ Preble, N. Amer. Fauna, 15:23, August 8, 1899.

_Zapus hudsonius campestris_, Bailey, N. Amer. Fauna, 49:117, January 8, 1927 (part).

_Type._--Adult female, skin and skull, No. 73673, U. S. Nat. Mus. Biol. Surv. Coll., Wingard, near Carlton House, Saskatchewan; obtained on July 23, 1895, by J. Alden Loring, original No. 3123.

_Range._--Most of southern half of Saskatchewan and Alberta, northeastern Montana southeastward to Aweme, Manitoba, and Webster, South Dakota. See fig. 46. Zonal range: Transition, Hudsonian, and Canadian.

_Description._--Size, small; back dark, usually with a distinct mid-dorsal band of black mixed with Warm Buff; sides lighter, more yellowish, but always with an admixture of black hairs; lateral line distinct, near Ochraceous-Buff, ventral surface characteristically suffused with Ochraceous-Buff; tail bicolored, grayish-white to yellowish-white below and pale brown above; hind feet grayish-white above; ears dark, edged with white or yellowish-white; skull small; postpalatal notch often anterior to posterior part of molars; inferior ramus of zygomatic process of maxillary often with well developed medial projection; auditory bullae flattened; nasals narrower anteriorly and proximal third depressed; base of zygomatic process of squamosal broad.

_Comparisons._--From _Zapus princeps princeps_, _Z. p. minor_ differs as follows: Size averaging smaller in all measurements taken, except least interorbital constriction which is approximately the same; color dorsally and laterally more yellowish, less Ochraceous-Buff; ventrally greater suffusion of Ochraceous-Buff.

For comparison with _Zapus princeps idahoensis_ see account of that subspecies.

_Remarks._--This geographic race is notably stable and retains most of its diagnostic characters throughout nearly all parts of its range. Intergradation occurs with _Zapus princeps idahoensis_ at various localities in Montana, as is described in more detail in the account of _idahoensis_. Crowe (1943:406) gives evidence of intergradation between _Zapus princeps idahoensis_ and _Z. p. minor_ in specimens from Entrance in western Alberta. Crowe (_loc. cit._) described these individuals as intermediate in color (lateral line present, under parts washed with buff, sides and dorsal stripe rich in ochraceous), and in cranial characters (smaller skulls, anteriorly narrower nasals, shorter more deflected rostrum, and higher cranium); but he considered them closer to _Z. p. minor_.

A skin without skull from Kananaskis Valley, Alberta, shows intergradation between _Z. p. idahoensis_ and _Z. p. minor_. This individual is like _Z. p. idahoensis_ in dorsal and lateral coloring, but is nearer _Z. p. minor_ in ventral coloring and in the presence of a distinct lateral line. External measurements provide basis for tentatively assigning the skin to _Z. p. minor_.

_Specimens examined._--Total, 118, distributed as follows:

ALBERTA: 4 mi. N Marinville, 2; Blindman River, 1 (USBS); Camrose, 1 (ROM); Red Deer River, 1 (USBS); Didsbury, Little Red Deer River, 1 (ROM); Kananaskis Valley, 7000 ft., 1 (ROM); High River, 2 (ROM); Lodge Creek, 2 (NMC).

MANITOBA: Shoal Lake, 6 (NMC); Oak Lake, 4 (NMC); Aweme, 7 (6 ROM; 1 USBS).

MONTANA: _Chouteau County_: Eagle Creek, 25 mi. SE Big Sandy, 3 (UM). _Hill Co._: Fort Assiniboine, 1 (USBS); _Bear Paw Mt's, 20 mi. SE Fort Assiniboine_, 4 (USBS); _head Eagle Creek, Bear Paw Mt's_, 7 (UM). _Valley Co._: Glasgow, 1 (USBS).

NORTH DAKOTA: _Benson Co._: 4 mi. W Leeds, 1400 ft., 2; _2 mi. W Fort Totten, 1400 ft._, 13; Fort Totten, 4 (USBS). _Bottineau Co._: 4-8/10 mi. N Bottineau, 2100 ft., 2; _3-1/2 mi. N Bottineau, 1920 ft._, 2; _2-1/10 mi. N Bottineau, 1800 ft._, 3; _Bottineau_, 1 (USBS). _Dickey Co._: Oakes, 3 (USBS). _Grand Forks Co._: Larimore, 3 (USBS). _Montrail Co._: 6 mi. N Lostwood, 2 (USBS). _Nelson Co._: Stump Lake, 1 (USBS). _Richland Co._: _Lidgerwood_, 1 (USBS); 4 mi. S Blackner, (USBS). _Rolette Co._: St. John, 1 (USBS). _Sargent County_: _7-1/5 mi. E and 1-1/5 mi. S Oakes, 1200 ft._, 6; _3 mi. W Cayuga, 1000 ft._, 2. _Walsh Co._: Grafton, 2. _Ward Co._: _Minot_, 3 (CMNH). _Williams Co._: Grinnell, 2 (USBS); Buford, 2 (USBS).

SASKATCHEWAN: Wingard, near Carlton House, 2 (USBS); Fort Carlton, 1 (MVZ); Indian Head, 2 (USBS); Cypress Hills, N Maple Creek, 18 (NMC); _Battle Creek_, 1 (NMC).

SOUTH DAKOTA: _Day Co._: Webster, 1 (Chic. AS).

_Marginal records._--Saskatchewan: Wingard, near Carlton House; Fort Carlton. Manitoba: Shoal Lake; Aweme. North Dakota: Larimore; 4 mi. S Blackner. South Dakota: Webster. North Dakota: Oakes; Grinnell. Montana: Eagle Creek, 25 mi. SE Big Sandy. Alberta: High River; Kananaskis Valley, 2000 ft.; Red Deer River; Blindman River; 4 mi. N Marinville.

=Zapus princeps oregonus= Preble

_Zapus princeps oregonus_ Preble, N. Amer. Fauna, 15:24, August 8, 1899.

_Zapus major_ Preble, N. Amer. Fauna, 15:24, August 8, 1899, type from Warner Mt's, Lake County, Oregon.

_Zapus princeps major_, Hall, Univ. California Publ. Zool., 37:10, April 10, 1931.

_Zapus nevadensis_ Preble, N. Amer. Fauna, 15:25, August 8, 1899, type from Ruby Mt's, Elko County, Nevada.

_Zapus princeps nevadensis_, Hall, Univ. California Publ. Zool., 37:10, April 10, 1931.

_Zapus princeps palatinus_ Hall, Univ. California Publ. Zool., 37:8, April 10, 1931, type from Wisconsin Creek, 7800 ft., Toyabe Mt's, Nye County, Nevada.

_Zapus princeps princeps_, Anthony, Bull. Amer. Mus. Nat. Hist., 33:17, March 17, 1913.

_Type._--Male, adult, skin and skull; No. 78156, U. S. Nat. Mus. Biol. Surv. Coll.; Elgin, Blue Mountains, Union Co., Oregon; obtained on May 29, 1896, by Edward A. Preble, original No. 959.

_Range._--Southeastern Washington, eastern Oregon east of Cascades, northeastern California, central and northeastern Nevada, and southwestern Idaho. See fig. 46. Zonal range: Transition and Canadian.

_Description._--Size large; back from near Light Ochraceous-Buff to near Cinnamon-Buff, usually overlaid with black hairs forming broad dorsal band, which in some individuals is almost black; sides lighter than back, from near Light Pinkish-Cinnamon to near Cinnamon-Buff and Ochraceous-Buff, often with black hairs interspersed; lateral line faintly marked or wanting; belly pure white; tail bicolored, grayish-brown above and grayish-white to yellowish-white below; ears dark, edged with color of sides; palatal bridge long; interorbital region broad; inferior ramus of zygomatic process of maxillary usually with median projection; auditory bullae relatively small; incisive foramina greatly enlarged posteriorly; tooth-rows divergent anteriorly; nasals narrow posteriorly.

_Comparisons._--From _Zapus princeps curtatus_, _Z. p. oregonus_ differs as follows: Size averaging larger; upper parts darker; tooth-rows more divergent anteriorly; palatal bridge longer; mastoid region broader; incisive foramina relatively wider posteriorly.

For comparisons with _Zapus princeps cinereus_, _Zapus princeps pacificus_ and _Zapus princeps idahoensis_ see accounts of those subspecies.

_Remarks._--The coloration in _Z. p. oregonus_ varies somewhat from north to south. In the northern part of the range the average coloration of the upper parts is darker with more ochraceous on the sides. To the southward the upper parts are progressively paler and the sides are near Light Pinkish-Cinnamon. Because of this variation of color, and because of the small samples available to workers in the past, three populations of this subspecies have been named as distinct. However, with the large amount of additional material now available, the supposed diagnostic characters of these "forms" prove to be within the range of individual variations of each of several populations of which large samples are available.

_Zapus major_ Preble (1899:24) was described as having zygomata short, palate broad and long, incisive foramina large and elliptical, and color dark. Some specimens of _Z. p. oregonus_, from nearly all parts of its geographic range, show these same characters. Resemblances in anteriorly divergent tooth-rows, broad interorbital region, small auditory bullae, and posteriorly narrow nasals, are additional reasons for placing _Z. major_ as a synonym of _Z. p. oregonus_.

_Zapus nevadensis_ Preble (1899:25), here considered a synonym of _Z. p. oregonus_, was described as having: auditory bullae small, posterior border of the palate usually convex anteriorly, palatal bridge long, and color pale. These characters, however, are within the range of individual variation of _Zapus p. oregonus_. Similarities such as tooth-rows diverging anteriorly, nasals narrow posteriorly, interorbital region broad, and incisive foramina enlarged posteriorly are added reasons for placing _Z. nevadensis_ as a synonym of _Z. p. oregonus_.

_Zapus princeps palatinus_ Hall (1931:8) was described as having: palatal bridge long, incisive foramina wide posteriorly, posterior border of palate straight or convex posteriorly, and color pale. These characteristics are to be found in some individuals in most populations of _Z. p. oregonus_. Additional well marked cranial similarities, such as small auditory bullae, broad interorbital region, and nasals narrow posteriorly offer additional evidence as to the close relationship of _Z. p. palatinus_ and _Z. p. oregonus_. Hall (_loc. cit._), with a small sample available to him for comparative purposes (14 specimens of _Z. p. palatinus_ and 12 specimens of _Z. p. nevadensis_), was impressed by the condition of the palate in _Z. p. palatinus_ and wrote: "the generally straight, or even posteriorly convex, posterior border of the palate seems to be unique among described forms of _Zapus_. The name _palatinus_ is given in allusion to this structural feature." With more than 300 specimens of _Z. p. oregonus_ available for study I find that a straight or posteriorly convex posterior border of the palate occurs in more than 50 per cent of the individuals examined. Specimens displaying this described palatal condition are known from all parts of the range of _Z. p. oregonus_, but do occur in a higher percentage of specimens in the area ascribed by Hall (_loc. cit._) to the range of _Z. p. palatinus_.

Intergradation with _Zapus princeps idahoensis_ and _Zapus princeps cinereus_ is discussed in the accounts of those subspecies.

_Specimens examined._--Total, 340, distributed as follows:

CALIFORNIA: _Modoc Co._: Buck Creek R. S., 1 (CAS); _Willow Ranch_, 4 (CAS); _Sugar Hill, 5000 ft._, 1 (MVZ); _Goose Lake Meadows, near Sugar Hill_, 4 (MVZ); _Parker Creek, Warner Mts., 5500 ft._, 18 (MVZ); _Dry Creek, Warner Mts., 4800 ft._, 3 (MVZ) _east face Warner Peak, Warner Mts., 8700 ft._, 1 (MVZ); _5 mi. NW Eagle Peak, 7000 ft._, 5 (MVZ); Lassen Creek, 1 (SDM); _Happy Camp_, 1 (CAS).

IDAHO: _Boise Co._: Bald Mtn. R. S., Boise Nat'l Forest, 10 mi. S. Idaho City, 7400 ft., 2 (USBS). _Elmore Co._: Trail Creek, Boise Nat'l Forest, 2 (USBS). _Washington County_: 1 mi. NE Heath, SW Slope Cuddy Mtn., 4000 ft., 20 (5 MVZ).

NEVADA: _Elko County_: _6 mi. SW Mountain City, Cobb Creek, 6500-6550 ft._, 44 (MVZ); _summit between heads of Copper and Coon creeks, Jarbidge Mts._, 18 (9 MVZ); _head of Ackler Creek, 6800 ft._, 2: Steel Creek, 7000 ft., 11 (4 MVZ); _summit of Secret Pass, 6200 ft._, 8; _south fork Long Creek, 7830 ft._, 4; Harrison Pass R. S., Green Mtn., Canyon, 6050 ft., 12. _Eureka County_: 4 mi. S Tonkin, Denay Creek, Roberts Mt's, 1 (MVZ). _Humboldt County_: _Martin Creek R. S._, 1 (MVZ); 13 mi. N Paradise Valley, 6700 ft., 19 (MVZ). _Lander County_: Kingston R. S., 7500 ft., 4 (MVZ). _Nye County_: Wisconsin Creek, 7000 ft., 12 (MVZ). _White Pine County_: Willow Creek, 2 mi. S Elko County line, Ruby Mts., 6500 ft., 24 (2 MVZ).

OREGON: _Baker Co._: East Pine Creek, 2-1/2 mi. NE Cornucopia, 6 (USBS); McEwen, 2 (USBS); _Bourne_, 7 (USBS). _Clackamas County_: _Marks Creek, 12 mi. N of Howard_, 2 (USBS); Howard, 2 (USBS). _Crook County_: _Ochoco R. S., 4000 ft._, 4 (MVZ). _Grant Co._: _Austin_, 2 (USBS); _Cold Spring, 4900 ft., 8 mi. E Austin_, 4 (MVZ); Beech Creek, 1 (USBS); _Strawberry Mts._, 6 (USBS); _north fork Malheur River, 21 mi. SE Prairie City, 5000 ft._, 21 (MVZ). _Harney Co._: 10 mi. N. Harney, 1 (USBS); _Steen Mts., Keiger Gorge, 6900 ft._, 6 (USBS); Diamond, 4300 ft., 2 (USBS). _Jefferson Co._: Foley Creek, 12 mi. E Hay Creek, 1 (USBS). _Klamath Co._: Fort Klamath, 1 (USBS). _Lake Co._: Silver Creek, 7000 ft., Yamsey Mts., 1 (USBS); _2 mi. E Lakeview, 5200 ft._, 3 (MVZ). _Malheur Co._: Jordan Valley, 4200 ft., 1 (USBS). _Umatilla Co._: Meacham, 1 (USBS). _Union County_: Elgin, 2 (USBS). _Wallowa Co._: Paradise, 10 mi. N Horse Creek, 7000 ft., 1 (USBS); _Minam Lake_, 1 (USBS); _16 mi. S and 3 mi. E Lostine, 5500 ft._, 9 (MVZ); _west fork Wallowa River, 5000 ft., 2-1/2 mi. above Wallowa Lake_, 1 (FM); _near Wallowa Lake, 4500 ft._, 3 (FM). _Wheeler County_: 11 mi. W and 7 mi. S Mitchell, 4850 ft., 20 (MVZ).

WASHINGTON: _Asotin Co._: Anatone, 3300 ft., 1 (USBS). _Columbia County_: Twin Buttes, 25 mi. SE Dayton, Blue Mts., 2 (MVZ); _Stayawhile Spring, 5150 ft._, 4 (MVZ).

_Marginal records._--Washington: Anatone, 3300 ft. Oregon: East Pine Creek, 2-1/2 mi. NE Cornucopia. Idaho: 1 mi. NE Heath, SW slope Cuddy Mtn., 4000 ft.; Bald Mtn., R. S., Boise Nat'l Forest, 10 mi. S. Idaho City, 7400 ft.; Trail Creek, Boise Nat'l Forest. Nevada: Harrison Pass R. S., Ruby Mts.; Steel Creek, 7000 ft.; Wisconsin Creek, 7000 ft.; 13 mi. N Paradise Valley, 6700 ft. California: Lassen Creek; Buck Creek R. S. Oregon: Fort Klamath; Howard; Meacham. Washington: Twin Buttes, 25 mi. SE Dayton, Blue Mts.

=Zapus princeps pacificus= Merriam

_Zapus pacificus_ Merriam, Proc. Biol. Soc. Washington, 11:104, April 26, 1897; Preble, N. Amer. Fauna, 15:30, August 8, 1899.

_Jaculus hudsonius_, Baird, Repts. Expl. and Surv. 111 8 (pt. 1):433, July 14, 1858 (part--the part from Canoe Creek, California).

_Zapus alleni_ Elliot, Field Columbian Mus., publ. 27, zool. ser., 1:212, April 19, 1898, type from Pyramid Peak, Lake Tahoe, El Dorado County, California.

_Zapus trinotatus alleni_, Elliot, Field Columbian Mus. Publ. 91, zool. ser., 3:315, July 5, 1904; Preble, N. Amer. Fauna, 15:27, August 8, 1899.

_Zapus pacificus alleni_, Howell, Univ. California Publ. Zool., 21:232, May 20, 1920.

_Zapus trinotatus pacificus_, Bailey, N. Amer. Fauna, 55:233, August 29, 1936.

_Zapus princeps alleni_, Hall, Mammals of Nevada; Univ. California Press, Berkeley, California, 579, July 1, 1946.

_Type._--Male, subadult, skin and skull, No. 80445, U. S. Nat. Mus. Biol. Surv. Coll.; Prospect, Rogue River Valley, Jackson Co., Oregon; obtained on August 29, 1896, by Edward A. Preble, original No. 1454.

_Range._--Sierra Nevada Mt's, from Kern Peak, Tulare County, California, northeastward to Mt. Rose, Washoe County, Nevada, then northwestward through the Trinity and Salmon mountains, California, to the upper Rogue River Valley, Oregon, thence southwestward to South Yolla Bolly Mt'n, Tehama County, California. See fig. 46. Zonal range: Transition, Canadian, and Hudsonian.

_Description._--Size medium; color bright; back near Ochraceous-Buff with admixture of black hair forming dark dorsal band; sides bright Ochraceous-Buff with fine admixture of black hair; lateral line blending with color of sides or wanting or indistinct; ventral surface white; tail bicolored, grayish-brown above, yellowish-white below, in some specimens with white tip; feet grayish-white above; ears dark, edged with Ochraceous Buff; braincase relatively narrow; incisive foramina relatively short; pterygoid fossae usually broad; proximal part of inferior ramus of zygomatic process of maxillary broad; postpalatal notch usually broadly rounded; auditory bullae relatively small and flattened; nasals parallel sided; maxillary tooth-row short; interorbital region moderately broad.

_Comparison._--From _Zapus princeps oregonus_, _Z. p. pacificus_ differs in being brighter in all pigmented areas; more ochraceous and less yellow laterally; dorsally more ochraceous and less black; size averaging smaller; maxillary tooth-rows shorter; auditory bullae less inflated and smaller; interorbital region averaging narrower; palatal bridge averaging shorter; incisive foramina shorter and posteriorly narrower; nasals parallel rather than narrowed posteriorly.

_Remarks._--Original describers considered both _Z. pacificus_ and _Z. alleni_ as specifically distinct from _Z. trinotatus_. Merriam (1897a:104) named _Z. pacificus_ and gave the following diagnostic characters: short rostrum and nasals; small auditory bullae; basioccipital broad between bullae. Elliot (1898:212) named _Z. alleni_ and ascribed to it the following diagnostic characters: cranium long and narrow; nasals same breadth for entire length; palate wide; pterygoid fossae wide posteriorly; auditory bullae small; basisphenoid and basioccipital wide; upper tooth-rows short. Preble (1899:27) considered _Z. alleni_ to be a subspecies of the species _Z. trinotatus_, remarking that the skulls are similar to those of _Z. trinotatus_ but smaller with much smaller bullae; in coloration the animals are lighter above and without fulvous below. Preble remarked that the skull of _Z. alleni_ differs so greatly from that of _Z. montanus_ that comparison was not required. Preble (_op. cit._:30) treated _Z. pacificus_ as a full species. Howell (1920:233) considered _Z. pacificus_ and _Z. alleni_ to be subspecies of _Z. pacificus_. Howell (_loc. cit._) pointed out size, cranial, and color similarities between the two, and remarked that _pacificus_ is clearly distinct from _Z. montanus_, its nearest geographic neighbor. Hall (1946:578) arranged _Z. alleni_ as a subspecies of _Z. princeps_, although not on grounds wholly satisfactory to him because actual intergrades between _alleni_ and neighboring races of _princeps_ were not available.

I here consider _Z. alleni_ to be synonymous with _Z. pacificus_; the latter is a subspecies of _Z. princeps_. Certain diagnostic characters, such as the shape and size of the os penis, the diameter and pigment pattern of the hair, the over-all proportions of the skull, and the size and shape of the teeth indicate that _alleni_ and _princeps_ belong to the same species, even though animals from intermediate geographic areas are not available to show actual intergradation.

The diagnostic characters referred to in the original description of _Z. alleni_, as given earlier in this account, agree with characters of specimens of _Z. p. pacificus_. Howell (1920:233) remarks that, in coloration and length of foot, typical _alleni_ differs but slightly from _pacificus_. Howell (_loc. cit._) noted, as I also have, that there are slight cranial differences in specimens from various parts of the range of _Z. p. pacificus_; these variations are somewhat clinal in nature, cranial dimensions showing a slight increase from south to north. The largest animals occur in western Tehama, Trinity, and Siskiyou counties, California. Samples from various localities in Jackson County, Oregon, are slightly smaller than these, but are larger than specimens from the southern Sierra Nevada.

_Specimens examined._--Total, 264, distributed as follows:

CALIFORNIA: _Alpine County_: _Carson River, 1/4 mi. SW Woodfords, 5700 ft._, 3 (MVZ); _Diamond Valley, 5500 ft., 1 mi. SE Woodfords_, 6 (MVZ); _Faith Valley_, 1 (MVZ). _El Dorado County_: _Glen Alpine Creek, near Fallen Leaf Lake, 6600 ft._, 8 (MVZ); _1 mi. W Fyffe_, 1 (MVZ); _Fresno County_: _Hume_, 1 (MVZ). _Mariposa County_: _Chinquapin, 6700 ft., Yosemite Nat'l Park_, 12 (MVZ); _E fork Indian Canyon, 7300 ft._, 8 (MVZ); _Merced Grove, Big Trees_, 7 (MVZ); _1 mi. E Merced Lake_, 5 (MVZ); _near Mono Meadow, Yosemite Nat'l Park_, 4 (MVZ); _near Mt. Hoffman, 8100 ft., Yosemite Nat'l Park_, 5 (MVZ); _Porcupine Flat, 8100 ft., Yosemite Nat'l Park_, 9 (MVZ); _Yosemite Creek, Yosemite Valley_, 7 (MVZ); foot Yosemite Falls, Yosemite Nat'l Park, 8 (MVZ). _Mono County_: _Walker Lake, 8000 ft._, 5 (MVZ); _Swager Canyon, 7800 ft._, 3; Mono Lake P. O. 6500 ft., 4 (MVZ). _Placer Co._: Truckee River, Squaw Creek, 1 (SDM); _W bank Truckee River_, 1 (MVZ). _Plumas County_: Rich Gulch, 3850 ft., 11 mi. W and 8 mi. N Quincy, 2 (MVZ). _Shasta County_: Warner Creek, 8000 ft., Lassen Peak, 6 (MVZ). _Siskiyou Co._: _Donomore Meadow, 5800 ft., 15 mi. W Hilt_, 7 (MVZ); Poker Flat, 5000 ft., 12 mi. NW Happy Camp, 7 (MVZ); Little Shasta, 1 (USBS); Siskiyou Mts., 6000 ft., 2 (USBS); _Sisson_, 1 (SDM); _Mt. Shasta, 6500 ft._, 6 (MVZ). _Salmon River Divide_, 2 (MVZ); _S fork Salmon River, 5000 ft._, 7 (MVZ). _Tehama County_: _2 mi. W Black Butte, on Lassen Rd., 6800 ft._, 5 (MVZ); _2 mi. E Mineral, 5200 ft._, 2 (MVZ); 2 mi. S Yolla Bolly Mtn., 11 (MVZ). _Trinity Co._: _N fork Coffee Creek, 4500 ft._, 34 (MVZ); Canyon Creek, 4 (USBS); 8 mi. NE Hyampon, 2900 ft., 1 (MVZ); _3 mi. NNW Mad River Bridge, 2900 ft., South Fork Mtn._, 5 (MVZ); _1-1/2 mi. N Mad River Bridge, 3000 ft., South Fork Mtn._, 6 (MVZ); _1 mi. SW North Yolla Bolly Mtn._, 14 (11 MVZ); _1/2 mi. S South Yolla Bolly Mtn._, 3 (MVZ). _Tulare County_: _Jordan Hot Springs, Sierra Nevada Mts., 6700 ft._, 9 (MVZ); _Sherman Creek, Sequoia Nat'l Park_, 1 (MVZ); _Tokopah Valley, 7000 ft., Sequoia Nat'l Park_, 1 (MVZ); 2 mi. E Kern Peak, 9300 ft., Sierra Nevada Mts., 1 (MVZ). _Tuolumne County_: _head Lyle Canyon, Yosemite Nat'l Park, 10,000 ft._, 9 (MVZ); _Tuolumne Meadows, 8600 ft., Yosemite Nat'l Park_, 1 (MVZ).

NEVADA: _Douglas County_: 1/2 mi. E Zephyr Cove, Lake Tahoe, 6400 ft., 1 (MVZ). _Ormsby County_: _S end Marlette Lake, 8000 ft._, 2 (MVZ); _1/2 mi. S Marlette Lake, 8150 ft._, 3 (MVZ). _Washoe County_: _1/2 mi. S Mt Rose, 9500 ft._, 3 (2 MVZ); 3 mi. S Mt. Rose, 8500 ft., 3 (MVZ).

OREGON: _Jackson Co._: Prospect, 3 (2 USBS, 1 MVZ); _W slope Grizzly Peak, 4600 ft._, 1 (USBS); _Siskiyou_, 1 (USBS); Longs Camp, N base Ashland Peak, 3300 ft., 1 (USBS).

_Marginal records._--Oregon: Prospect. Nevada: 3 mi. S Mt. Rose, 8500 ft.; 1/2 mi. E Zephyr Cove, Lake Tahoe, 6400 ft. California: Mono Lake P. O., 6500 ft.; 2 mi. E Kern Peak, 9300 ft., Sierra Nevada Mts.; Rich Gulch, 3850 ft., 11 mi. W and 8 mi. N Quincy; Warner Creek, 8000 ft., Lassen Peak; 2 mi. S Yolla Bolly Mtn.; 8 mi. NE Hyampon, 2900 ft.; Siskiyou Mts., 6000 ft.; Poker Flat, 5000 ft., 12 mi. NW Happy Camp.

=Zapus princeps princeps= J. A. Allen

_Zapus princeps_ J. A. Allen, Bull. Amer. Mus. Nat. Hist., 5:71-72, April 28, 1893; Preble, N. Amer. Fauna, 15:23, August 8, 1899.

_Type._--Female, adult, skin and skull; No. 5260/4140, Amer. Mus. Nat. Hist.; Florida, La Plata County, Colorado; obtained on June 27, 1892, by Charles P. Rowley.

_Range._--Sierra Madre, Medicine Bow, Laramie, and Big Horn mountains of Wyoming southward through Colorado into the Taos and San Juan mountains in northern New Mexico. See fig. 46. Zonal range: Transition, Canadian and Hudsonian.

_Description._--Size, medium; back dark usually with broad mid-dorsal band of black mixed with Warm Buff or Ochraceous-Buff; sides light (Warm Buff) but varying to Ochraceous-Buff, always with admixture of black hair; lateral line distinct and broad, varying from Light Ochraceous-Buff to Ochraceous-Buff; ventral surface white to base of hairs, frequently suffused with Ochraceous-Buff; tail indistinctly bicolored, tan to grayish-white below and pale brown above; hind feet grayish-white above; ears edged with white or yellowish-white; skull medium; large medial projection on inferior ramus of zygomatic process of maxillary; palate moderately long; postpalatal notch usually broadly rounded and posterior to posterior part of last molar; proximal part of inferior ramus of zygomatic process of maxillary broad; pterygoid fossae broad; auditory bullae moderately inflated.

_Comparisons._--From _Zapus princeps luteus_, _Z. p. princeps_ differs as follows: Total length, tail and hind foot longer; color darker, being less ochraceous; ears darker, edged with white or yellowish-white instead of Ochraceous-Buff; lateral line more distinct; skull larger, except least interorbital breadth which is smaller; auditory bullae larger, more inflated; pterygoid fossae larger; incisive foramina broader, longer, and posteriorly more truncate; nasals broader, tapering less distally.

From _Zapus princeps idahoensis_, _Z. p. princeps_ differs in: Size larger; darker with more Ochraceous-Buff; lateral line much more distinct; underparts frequently suffused with Ochraceous-Buff rather than seldom so; skull larger as regards length of palatal bridge, length of zygomatic arch, and width of proximal part of inferior ramus of zygomatic process of maxillary; pterygoid fossae broader; medial projection on inferior ramus of zygomatic process of maxillary large instead of reduced or absent; postpalatal notch usually anterior to, or on a plane with, posterior face of last molars rather than posterior to same.

_Remarks._--This subspecies retains most of its diagnostic characters in all parts of its geographic range. An individual from the type locality, Florida, Colorado, resembles _Zapus princeps luteus_ in color, but cranially is most nearly like _Z. p. princeps_. A specimen from Tierra Amarilla, New Mexico, a locality 25 miles north of, and in homogeneous habitat with, El Rito, New Mexico, from which specimens of _Z. p. luteus_ are known, shows resemblance to the latter in some cranial characters (see account of _Zapus princeps luteus_) but is most nearly like _Z. p. princeps_ to which it is referred.

Animals from Medicine Wheel Ranch, 9000 ft., 28 mi. E Lovell, Wyoming, which are here referred to _Z. p. princeps_, show intergradation with _Zapus princeps idahoensis_, being similar in size of pterygoid fossae, breadth of postpalatal notch, and in size and degree of inflation of the auditory bullae, but differ in color and in other cranial characters. Specimens from 2 mi. E Shriver, 6500 ft., Montana, which lack the distinct lateral line and ventral suffusion of Ochraceous-Buff, are here referred to _Z. p. idahoensis_.

_Specimens examined._--Total, 344, distributed as follows:

COLORADO: _Archuleta County_: _upper Navajo River_, 5 (CMNH); Navajo River, 6 (CMNH). _Boulder Co._: _12-1/2 mi. S Estes Park_, 2; _3 mi. S Ward_, 3; Gold Hill, 1 (USBS); _7 mi. NW Nederland's_, 2 (UM); _3 mi. E Pine Cliff_, 3 (CMNH). _Chaffee County_: _1-1/2 mi. S Monarch, 10,500 ft._, 2 (OKLA). _Conejos Co._: Antonito, 1 (USBS); _5 mi. S and 24 mi. W Antonito, 9600 ft._, 2. _Costilla Co._: _7 mi. SE Russell, 9200 ft._, 1 (MVZ); Fort Garland, 6 (USBS). _El Paso County_: Minnehaha, Half Way, 5 (UM). _Grand Co._: _Rocky Mtn. Nat'l Park_, 5 (UM). _Gunnison County_: Gothic, 10 (8 OKLA; 2 USBS); _Major Creek, foot of Monarch Pass_, 1 (OKLA). _Jackson Co._: Arapahoe Pass, Rabbit Ear Mts., 1 (USBS). _La Plata Co._: _7 mi. N Florida, Florida River, 7146 ft._, 8 (MVZ); Florida, 6500 ft., 11 (1 FM; 9 AMNH). _Larimer Co._: Elkhorn, 7000 ft., 1 (USBS); _19-1/2 mi. W and 2-1/2 mi. S Loveland, 7300 ft._, 3. _Mineral Co._: _Wasson Ranch, Creede_, 1; _3 mi. E Creede_, 1; _23 mi. S and 11 mi. E Creede, 9300 ft._, 5. _Rio Blanco Co._: _9-1/2 mi. SW Pagoda Peak, 7700 ft._, 5; Meeker, 1 (USBS). _Rio Grande County_: _Rock Creek Camping Area_, 1 (OKLA). _Saguache Co._: Saguache Park, Cochetopa Forest, 1 (USBS); _22 mi. W Saguache_, 1 (MVZ); _20 mi. S Saguache, Cochetopa Pass_, 1 (USBS). _San Juan County_: 6-1/2 mi. SW Silverton, 4.

NEW MEXICO: _Rio Arriba Co._: Tierra Amarilla, 1 (USBS). _Taos Co._: _Hondo Canyon, 8200 ft., west slope Taos Mts._, 1 (USBS); east slope Taos Mts., 8800 ft., 1 (USBS).

WYOMING: _Albany County_: 32 mi. N and 12-1/2 mi. E Laramie, 6080 ft., 1; _30 mi. N and 10 mi. E Laramie, 6760 ft._, 1; _29 mi. N and 8-3/4 mi. E Laramie, 6420 ft._, 6; _2 mi. S Browns Peak, 10,600 ft._, 2; _3 mi. ESE Browns Peak, 10,000 ft._, 8; _8 mi. E and 4 mi. S Laramie, 8600 ft._, 2; _8 mi. E and 6 mi. S Laramie, 8500 ft._, 1; _1 mi. ESE Pole Mtn., 8350 ft._, 2; _1-1/2 mi. ESE Pole Mtn., 8200 ft._, 1; _2 mi. SE Pole Mtn., 8300 ft._, 3; Centennial, 8120 ft., 1. _Big Horn County_: Medicine Wheel Ranch, 9000 ft., 28 mi. E Lovell, 36; _12 mi. E and 2 mi. N Shell, 7500 ft._, 13; _17 mi. E and 3 mi. S Shell, 9000 ft._, 1; _17-1/2 mi. E and 4-1/2 mi. S Shell, 9100 ft._, 6. _Carbon County_: Bridgers Pass, 18 mi. SW Rawlins, 7500 ft., 6; _Lake Marie, Medicine Bow Nat'l Forest, 10,400 ft._, 6; _14 mi. E and 6 mi. S Saratoga_, 5; _10 mi. N and 10 mi. E Encampment, 8000 ft._, 1; _10 mi. N and 12 mi. E Encampment, 7200 ft._, 2; _10 mi. N and 14 mi. E Encampment, 8000 ft._, 28; _9 mi. N and 3 mi. E Encampment_, 2; _8 mi. N and 8 mi. E Encampment, 8900 ft._, 1; _8 mi. N and 14 mi. E Encampment, 8400 ft._, 5; _8 mi. N and 14-1/2 mi. E Encampment, 8100 ft._, 12; _8 mi. N and 16 mi. E Encampment, 8400 ft._, 6; _8 mi. N and 22 mi. E Encampment, 10,000 ft._, 1; _8 mi. N and 19-1/2 mi. E Savery, 8800 ft._, 12; _8 mi. N and 20 mi. E Savery, 8800 ft._, 1; _7-1/2 mi. N and 18 mi. E Savery, 8400 ft._, 2; _7-1/2 mi. N and 18-1/2 mi. E Savery, 8400 ft._, 1; _7 mi. N and 18 mi. E Savery, 8400 ft._, 2; _6 mi. N and 13-1/2 mi. E Savery, 8400 ft._, 6; _6 mi. N and 14 mi. E Savery, 8350 ft._, 6; 4 mi. N and 8 mi. E Savery, 7300 ft., 1. _Converse County_: 21 mi. S and 24 mi. W Douglas, 7400 ft., 6; _21 mi. S and 24-1/2 mi. W Douglas, 7400 ft._, 3; _21-1/2 mi. S and 24-1/2 mi. W Douglas, 7600 ft._, 15; _22-1/2 mi. S and 24-1/2 mi. W Douglas, 7600 ft._, 1; _23 mi. S and 25 mi. W Douglas, 7800 ft._, 7. _Johnson County_: _6-1/2 mi. W and 2 mi. S Buffalo, 5700 ft._, 4; _5-1/2 mi. W and 1-1/2 mi. S Buffalo, 5520 ft._, 3; _5-1/2 mi. W and 1 mi. S Buffalo, 4800 ft._, 1; 1 mi. W and 4/5 mi. S Buffalo, 4800 ft., 1. _Laramie County_: 5 mi. W and 1 mi. N Horse Creek P. O., 3. _Natrona County_: _2 mi. W and 7 mi. S Casper, 6370 ft._, 2. _Washakie County_: 9 mi. E and 5 mi. N Tensleep, 7400 ft., 2; 9 mi. E and 4 mi. N Tensleep, 7000 ft., 5.

_Marginal records._--Wyoming: Medicine Wheel Ranch, 9000 ft., 28 mi. E Lovell; 21 mi. S and 24 mi. W Douglas, 7400 ft.; 5 mi. W and 1 mi. N Horse Creek P. O. Colorado: Gold Hill; Minnehaha. New Mexico: E slope Taos Mts.; Tierra Amarilla. Colorado: Florida; 6-1/2 mi. SW Silverton; Meeker. Wyoming: Bridgers Pass, 18 mi. W Rawlins, 7500 ft.

=Zapus princeps saltator= J. A. Allen

_Zapus saltator_ J. A. Allen, Bull. Amer. Mus. Nat. Hist., 12:3-4, March 4, 1899; Preble, N. Amer. Fauna, 15:31, August 8, 1899.

_Zapus princeps_, Preble, N. Amer. Fauna, 15:23, August 8, 1899 (part--the part from Glacier, British Columbia).

_Zapus hudsonius_, Kermode and Anderson, Rep. Prov. Mus. Nat. Hist. for 1913:21, 1914.

_Zapus princeps saltator_, Hall, Univ. California Publ. Zool., 37:10, April 10, 1931.

_Type._--Female, subadult, skin and skull, No. 14408, Amer. Mus. Nat. Hist.; Telegraph Creek, British Columbia; obtained on August 23, 1897, by A. J. Stone.

_Range._--Southern Yukon and southeastern Alaska south in British Columbia, to Bella Coola Inlet and Glacier. See fig. 46. Zonal range: Canadian and Hudsonian.

_Description._--Size medium; back near Ochraceous-Buff, overlaid with black hairs forming dark dorsal band thickly flecked with ochraceous; sides lighter than back; lateral line usually distinct; belly pure white, sometimes faintly suffused with Ochraceous-Buff; tail bicolored, dark above and grayish-white below; hind feet grayish-white above; ears dark, edged with yellowish-white or Ochraceous-Buff; incisive foramina long, broad posteriorly; palatal bridge relatively short; postpalatal notch anterior to posterior border of last molars; proximal part of inferior ramus of zygomatic process of maxillary without enlarged median projection; zygomatic arch short.

_Comparisons._--For comparison with _Zapus princeps kootenayensis_ and _Zapus princeps idahoensis_ see accounts of those subspecies.

_Remarks._--The geographic range of _Z. p. saltator_, as here understood, includes several localities heretofore considered to be within the geographic ranges of neighboring subspecies. Specimens from Indianpoint Lake, 15 mi. N of Barkerville, British Columbia, for example, which Hall (1934:379) considered nearer _Z. p. princeps_, are here referred to _Z. p. saltator_, with which they closely agree in cranial measurements and color of pelage. One individual from Glacier, British Columbia, thought to be _Z. p. princeps_ by Preble (1899:32), is here considered to show intergradation between _Z. p. kootenayensis_ and _Z. p. saltator_ but is more nearly like _Z. p. saltator_ to which it is here referred. Intergradation between _Zapus princeps idahoensis_ and _Z. p. saltator_ is noted, in color and in shape and size of the incisive foramina, in a specimen from Vermilion Crossing, Kootenay, British Columbia. The majority of cranial characters show these animals to be referable to _Z. p. idahoensis_. Specimens from Mt. Revelstoke, 3400 ft., British Columbia, show intergradation in shape of auditory bullae, in breadth of pterygoid fossae, and in shape and size of antorbital foramina between _Z. p. idahoensis_ and _Z. p. saltator_. Resemblance in pelage and in the majority of cranial characters indicates that these specimens are best referred to _Z. p. saltator_.

_Specimens examined._--Total, 187, distributed as follows:

ALASKA: Taku River, 1 (MVZ).

BRITISH COLUMBIA: Atlin, 7 (6 CAS; 1 PM); _Deep Creek, 60 mi. above Telegraph Creek_, 1 (USBS); _Sawmill Lake, near Telegraph Creek_, 6 (MVZ); junction 4 mi. N Telegraph Creek, 1 (ROM); McDame Post, Dease River, 1 (USBS); _Stikine River, at Glenora_, 28 (MVZ); _Kispiox Valley, 23 mi. N Hazelton_, 3 (MVZ); _9-mi. Mtn., 4500 ft., NE Hazelton_, 1 (MVZ); Hazelton, 959 ft., 20 (MVZ); Bear River, 7 mi. N Bear Lake, 1 (USBS); Charlie Lake, Fort St. John, 1 (PM); _Moose River_, 2 (PM); Tupper Creek, 7 (PM); _Babine_, 2 (USBS); _Port Simpson_, 3 (USBS); 12 mi. N Summit Lake, Alaska Highway, 3300 ft., 3 (NMC); _Giscome_, 1 (USBS); _Ootsa Lake_, 3 (PM); Inverness, mouth Skeena River, 1 (USBS); W end Eutsuk Lake, 1 (PM); Wapiti, head of Middle Branches River, 1 (USBS); Hagensborg, 15 (NMC); _Stuie, Cariboo Mtn., 4700 ft._, 2 (NMC); Rainbow Mts., Mt. Brilliant, 5000 ft., 10 (NMC); N 7 Wistaria P. O., 13 (NMC); _Mt. McLean, Lillooet_, 1 (PM); Mt. Robson P. O., Mt. Robson Park, 1 (MVZ); _Indianpoint Lake, 15 mi. NE Barkerville_, 42 (29 MVZ; 18 PM); Cottonwood P. O., 2 (MVZ); Mt. Revelstoke, 3400 ft., 6 (PM); Glacier, 1 (ROM).

YUKON: Rose River, mile 95 on Canol Road, 1 (NMC).

_Marginal records._--Yukon: Rose River, mile 95 on Canol Road, British Columbia; McDame Post, Dease River; Charlie Lake, Fort St. John; Tupper Creek; Wapiti, head of Middle Branches River; Mt. Robson P. O., Mt. Robson Park; Mt. Revelstoke, 3400 ft.; Cottonwood P. O.; Rainbow Mts., Mt. Brilliant, 5000 ft.; Inverness, mouth Skeena River. Alaska: Taku River. British Columbia: Atlin.

=Zapus princeps utahensis= Hall

_Zapus princeps utahensis_ Hall, Occ. papers, Mus. Zool., Univ. Michigan, 296:3, November 2, 1934.

_Jaculus Hudsonius_, J. A. Allen, Bull. Essex Inst., 6:65, April, 1874 (part--the part concerning Great Salt Lake Valley, Utah).

_Zapus princeps princeps_, Wolfe, Jour. Mamm., 91:154, May 9, 1928.

_Zapus princeps idahoensis_, Davis, Recent Mammals of Idaho, Caxton Printers, Caldwell, Idaho, p. 341, April 5, 1939 (part--the part from southeast Idaho).

_Type._--Female, adult, skin and skull; No. 59153, Museum of Zoology, University of Michigan; Beaver Creek, 19 mi. S Manila, Daggett County, Utah; obtained on July 16, 1928, by A. and R. D. Svihla, original No. 176.

_Range._--Southeastern Idaho and extreme western Wyoming (Teton, Snake, and Uinta Mt's) southward through Uinta, Wasatch, Oquirrh, and Beaver Mt's of Utah. See fig. 46. Zonal range: Transition, Canadian, and Hudsonian.

_Description._--Size, large; back from Cinnamon-Buff to Warm Buff overlaid with black hairs; sides lighter with less admixture of black hairs; lateral line indistinct, sometimes wanting; tail bicolored, brownish-black above, white to yellowish-white beneath; feet grayish-white above; ventral surface white to base of hairs; ears dark, edged with white to yellowish-white; skull large; palatal bridge relatively short; upper tooth-rows diverging anteriorly; occipitonasal length great; interorbital region broad; zygomata widely bowed; postpalatal notch anterior to posterior face of last molars; mastoid width great.

_Comparisons._--From _Zapus princeps princeps_, _Z. p. utahensis_ differs in: color dorsally and laterally less ochraceous, lacking broad lateral line; skull larger in every part measured, excepting length of palatal bridge and breadth of palate at M3; zygomata more bowed; upper tooth-rows more divergent anteriorly; postpalatal notch anterior to posterior border of last molars.

Compared with _Zapus princeps cinereus_, _Z. p. utahensis_ differs as follows: Size averaging larger; upper parts darker, Cinnamon-Buff not Pinkish-Buff; incisive foramina wider posteriorly; palate wider; zygomata more robust.

For comparison with _Zapus princeps idahoensis_ see account of that subspecies.

_Remarks._--_Zapus princeps utahensis_ most closely resembles the several subspecies in the Great Basin in its large size, widely bowed zygomata, and posteriorly broadened incisive foramina. Intergradation between _Z. p. utahensis_ and _Zapus princeps cinereus_, geographically the nearest of the Great Basin subspecies, is not known. Intergradation in color and cranial characters occurs between _Zapus princeps idahoensis_ and _Z. p. utahensis_ in specimens from 17 mi. E and 4 mi. N of Ashton, Idaho. All these specimens are, however, referable to _Z. p. idahoensis_. Animals from 9 mi. SE Irwin and from 3 mi. SW Victor, Idaho, resemble _Z. p. utahensis_ in most differential characters (dorsally ochraceous, lateral line more distinct, incisive foramina large, palate broad anteriorly, auditory bullae less inflated), and are here referred to _Z. p. utahensis_. A series of specimens from the head of Crow Creek, Idaho, were considered by Davis (1939:340) to be intergrades between _Z. p. idahoensis_ and _Z. p. utahensis_; he thought that the specimens were more nearly like _Z. p. utahensis_ in color, but cranially (80 per cent in average ratio of anterior width of palate to posterior width of palate), more nearly like _Z. p. idahoensis_, to which subspecies he referred them. I have examined these specimens and find them to be more nearly like _Z. p. utahensis_ not only in color but in cranial characters as well. For example, the average ratio obtained by me for anterior width of palate to posterior width of palate is 72 per cent, rather than 80 per cent as given by Davis (_loc. cit._). Other cranial characters, size of the incisive foramina, shape of the foramen magnum, and shape of the auditory bullae, indicate relationship with _Z. p. utahensis_ to which they are here referred. Two immature individuals from Strawberry Creek, 20 mi. E Preston, Idaho, considered to be _Z. p. idahoensis_ by Davis (_op. cit._:341), also are here referred to _Z. p. utahensis_.

_Specimens examined._--Total, 178, distributed as follows:

IDAHO: _Bonnerville County_: _9 mi. SE Irwin, 6400 ft._, 3. _Caribou Co._: Head Crow Creek, Preuss Mts., 7500 ft., 6 (USBS). _Franklin County_: Strawberry Creek, 20 mi. NE Preston, 6700 ft., 2 (MVZ). _Teton County_: 3 mi. SE Victor, 6 (MVZ).

UTAH: _Beaver County_: Puffer Lake, 1 (UU). _Daggett County_: junction Deep Creek and Carter Creek, 7900 ft., 2 (UU). _Duchesne Co._: _Currant Creek, Uinta Forest_, 2 (USBS). _Morgan Co._: _exact locality not given_, 1 (UU). _Rich County_: 12 mi. SW Woodruff, 1 (MVZ). _Salt Lake County_: _Lambs Canyon, 2 mi. above Parleys Canyon, 7000 ft._, 1 (UU); _head Lambs Canyon, 9000 ft._, 3 (UU); _Salamander Lake and Lambs Canyon, 9000 ft._, 11 (UU); _"The Firs," Mill Creek Canyon_, 2 (UU); _Brighton, Silver Lake P. O., 8700 ft., Cottonwood Canyon_, 1 (UU); _Brighton, Big Cottonwood Canyon, 8000 ft._, 1 (UU); _1 mi. above Alta_, 4 (UU); Butterfield Canyon, approximately 5 mi. above Butterfield Tunnel, 3 (UU). _Sanpete Co._: _8 mi. E Fairview and 5 mi. S Mammoth R. S., Manti Nat'l Forest, 9000 ft._, 1 (USBS); _Baldy R. S., Manti Nat'l Forest_, 1 (UU); Ephraim, 8850 ft., 1 (USBS). _Summit County_: _Henrys Fork, Uinta Mts., 8000 ft._, 4 (UU); 14 mi. S and 2 mi. E Robertson, 9300 ft., 3. _Uintah County_: 21 mi. W and 15 mi. N Vernal, 10,050 ft., 1. _Utah County_: Payson Lake, 8300 ft., 12 mi. SE Payson, Mt. Nebo, 12 (UU); _1 mi. E Payson Lake, 8300 ft., Mt. Nebo_, 3 (UU). _Wasatch County_: Provo River, 3 mi. N Soapstone R. S., Wasatch Nat'l Forest, 1 (UU).

WYOMING: _Lincoln County_: 3 mi. N and 11 mi. E Alpine, 5650 ft., 37. _Teton County_: 1/4 mi. E Moran, 6700 ft., 4; _Bar B. G. Ranch, 6500 ft., 2-1/2 mi. NE Moose_, 11; _Moose, 6225 ft._, 1. _Uinta County_: 2 mi. E Robertson, 7200 ft., 1; _9 mi. S Robertson, 8000 ft._, 21; _9 mi. S and 2-1/2 mi. E Robertson, 8000 ft._, 1; _9-1/2 mi. S and 1 mi. W Robertson, 8600 ft._, 2; _10 mi. S and 1 mi. W Robertson, 8700 ft._, 18; _10-1/2 mi. S and 2 mi. E Robertson, 8900 ft._, 1; _13 mi. S and 1 mi. E Robertson, 9000 ft._, 4; _5 mi. E Lonetree_, 1 (ROM).

_Marginal records._--Wyoming: 1/4 mi. E Moran, 6700 ft.; 2 mi. E Robertson, 7200 ft. Utah: junction Deep Creek and Carter Creek, 7900 ft.; Paradise Park, 21 mi. W and 15 mi. N Vernal, 10,500 ft.; Ephraim, 8500 ft.; Puffer Lake; Payson Lake, 8300 ft., 12 mi. SE Payson, Mt. Nebo; Butterfield Canyon, approximately 5 mi. above Butterfield Tunnel. Idaho: Strawberry Creek, 20 mi. NE Preston, 6700 ft.; 3 mi. SW Victor.

=Zapus hudsonius= (Zimmerman)

(Synonymy under subspecies)

_Range._--From Pacific Coast of Alaska eastward to Atlantic Coast; from northern limit of tree-growth south into central Colorado and northeastern parts of Oklahoma and Georgia. See fig. 47.

_Externals._--Size small to medium (total length 188 mm to 216 mm); tail longer than head and body (112 mm to 134 mm) and bicolored, pale brown to brownish-black above, white to yellowish-white below; hind feet long (28 mm to 31 mm), grayish-white above; back ochraceous to dark brown; sides paler than back with dark hair interspersed; lateral line usually present but sometimes indistinct or entirely absent (when present usually clear Ochraceous-Buff); ventral coloration white, sometimes with suffusion of ochraceous; guard hairs average 115 microns (96u to 140u) in diameter; underhair with pigment pattern in form of hollow, narrow rectangles; cuticular scales of underhair large and fewer than those of the underfur of _Z. trinotatus_, but underhair of _Z. hudsonius_ otherwise resembles that of _Z. trinotatus_.

_Baculum._--Size small (total length 4.5 mm to 4.9 mm); base medium in width (0.64 mm to 0.72 mm); tip narrow (0.24 mm to 0.26 mm) and dished out in dorsal aspect, blunted; shaft rounded, curving gently upward at tip.

_Skull._--Small to medium and relatively narrow in relation to length; rostrum pointed and short; mastoid region relatively narrow; incisive foramina short; base of zygomatic process of squamosal narrow; coronoid process of mandible short, relatively weak. Upper premolar usually small (averaging .30 mm in length and .35 mm in breadth) sometimes functional (most often so in old adults), occlusal surface divided by single shallow re-entrant fold, which in worn teeth forms centrally located lake; tooth-row short as compared to that of other species; individual cheek-teeth usually smaller than those of other species; lower cheek-teeth shorter and narrower than those of other species; angle of mandible strongly inflected.

GEOGRAPHIC VARIATION

The species _Z. hudsonius_ is divisible into 11 subspecies based on differences in color, relative proportions of the tail, hind feet, body, and size and shape of parts of the skull (zygomata, braincase, incisive foramina, auditory bullae, pterygoid fossae, rostrum, and interorbital breadth).

Color of the pelage varies, as a general rule, from dark-backed, dull-sided individuals in the northern parts of the geographic range of the species to light-backed, bright-sided individuals in the southern parts of the range.

Individuals from the southernmost geographic races (_Z. h. americanus_ and _Z. h. pallidus_) are the smallest for the species and those from the northernmost subspecies (_Z. h. alascensis_) are the largest. One subspecies, _Z. h. campestris_, from the central part of the range of the species, however, seems to be out of the cline. This form inhabits the eastern foothills of the Rocky Mountains and is a robust animal approaching _Z. princeps_ in size.

Seemingly there is no clinal variation in the several qualitative features of the cranium, for instance in the shape of the auditory bullae, shape of the incisive foramina, and shape of the postpalatal notch. On the other hand, the dimensions of the entire skull show that the larger crania are of the northernmost subspecies and the smaller of the southernmost subspecies.

NATURAL HISTORY

_Habitat._--_Zapus hudsonius_ occurs in low undergrowth usually of grasses or forbs or both, in open coniferous forests, deciduous hardwood groves, or in stands of tall shrubs and low trees, but most frequently in open, moist areas.

Quimby (1951:75) notes that jumping mice were more common in the moist lowlands than in the drier uplands. More were in the open type lowlands than in the forested type, and these mice favored habitats normally bordered by small streams affording moist to semi-aquatic living conditions. The reports of Goodwin (1924:255), Christian (1936:416), G. S. Miller (1899:329), Cory (1912:249), Lyon (1936:277), Stoner (1918:123), and others, although concerning widely different parts of North America, indicate that _Z. hudsonius_ selects habitats in vegetation of like form, even though different assemblages of plant species may be involved.

An average of 11.91 mice per acre was recorded by Quimby (1951:91) from a study plot at Itasca Park, Clearwater County, Minnesota. He gives the monthly population densities per acre for _Z. hudsonius_ at Centerville, Anoka County, Minnesota, as follows: June 2.78, July 3.57, August 3.10, and September 1.81. Blair's (1940:248) data on bi-monthly population density per acre for _Z. hudsonius_ on the Edwin S. George Reserve, Livingston County, Michigan, are remarkably similar, when adjusted on a monthly basis, to those obtained by Quimby (_loc. cit._). Blair's (_loc. cit._) monthly population densities per acre are as follows: June 3.90, July 3.85, August 3.10, and September 2.00. Townsend (1935:90) estimated population densities per acre for _Z. hudsonius_ in central New York state, at 11 to 72 individuals. As Quimby (1951:92) points out, Townsend's figures are probably too high, as commonly is the case when the moving quadrat technique is used because animals from neighboring areas enter the trapped area to take over the niches made available by their predecessors' removal.

The population of _Z. hudsonius_ may vary considerably from year to year as well as seasonally. Blair (1940:249) found notably fewer jumping mice on the George Reserve in 1938 than in 1939. Quimby (1951:94) found the numbers of _Zapus_ to be highly variable and thought that there was a rapid turnover. Young animals were not caught until July when 25 per cent were either juveniles, young, or subadults; from this time on these age classes increased to a high of sixty-one per cent in September. Quimby (_loc. cit._) found that separating the individuals into their proper age classes was more difficult in September, since the young from early litters are adultlike in appearance. His data indicate as he remarked, "That the over-wintering adults are, for the most part, gradually replaced by the young of the year as the summer progresses."

The sexes in _Z. hudsonius_ vary only slightly from a one to one ratio. Quimby (1951:63) found a sex ratio of 110 females to 100 males and Blair (1940:245) records a sex ratio of 113 males to 100 females. Townsend (1935:42) records a sex ratio in central New York of 155 males to 100 females. Such a wide variation from a one to one ratio suggest that the moving quadrat technique, which Townsend (1935:90) employed in obtaining his data, may be, in some way unknown to me, more selective for the males.

_Behavior._--The saltatorial powers of _Z. hudsonius_ are well developed and often have been described in the literature. Stoner (1918:123) remarks that, "When disturbed _hudsonius_ moves away by a series of leaps ... the distance traversed in one of these leaps is from six to eight feet."; Cory (1912:249) observed these mice to make surprisingly long leaps, and, according to him, a distance of 10 feet is by no means unusual; Handley and Patton (1947:49) credit these animals with jumping eight to ten feet at a single bound; Hamilton (1935:190) remarked that he noted an average of not more than four to six feet per jump; Townsend (1935:91) observed one individual make jumps of about two feet; and Harper (1932:29) records a jumping mouse leaping for distances of two to three feet. Quimby (1951:72) notes that he had never seen one jump farther than three feet. He found that the greatest jumps occurred initially and normally covered a distance of two to three feet; subsequent leaps were shorter but more rapid. A jumping mouse in full retreat progressed by jumps of about one foot.

Statements concerning the gait of _Z. hudsonius_ are not in agreement but the consensus of opinion is that these animals when unfrightened progress by a series of hops of one to six inches, or, occasionally, with a slow creeping motion while the animal is on all fours. When frightened, however, their progress is by long bounds; the mice make a series of two or three such leaps to the nearest protective cover, and then sit motionless until pursued.

Concerning the use of the tail as a balancing organ, G. S. Miller (1899:330) describes the behavior of a jumping mouse from which the tail had been severed by the sickle of a mowing machine. "When I approached, it made violent efforts to escape, but the moment it was launched in the air, its body, deprived of its balancing power, turned end over end so that it was as likely as not to strike the ground facing the direction from which it had come."

Riparian animals such as _Z. hudsonius_ need enter the water to escape from enemies or perhaps in search of food. _Zapus hudsonius_ can and does swim. Hamilton (1935:190) found it to be a strong swimmer capable of remaining in the water for from four to five minutes. According to Hamilton (_loc. cit._), when the mouse is swimming the head is held high, the tail is arched near its middle, and only the hind limbs are employed in propulsion. According to Sheldon (1938:327), Philip Allan, in northern Minnesota, saw many _Z. hudsonius_ swimming three or four inches under the surface of the water. The mice swam upstream and only the hind legs were employed in the swimming movements. N. A. Preble (1944:200), at Archer's Pond, 3 miles southeast of Center, Ossipee County, New Hampshire, observed a jumping mouse swimming rapidly under water toward another portion of the shore 30 or 40 feet away. The mouse, swimming less than a foot beneath the surface, was vigorously using both forefeet and hind feet, but the long tail trailing limply behind, contributed in no way to the animal's movements. Quimby (1951:72) released five of the mice, one at a time, in the open water of a lake. He followed alongside in a boat and observed that, "In all instances the animals proved to be excellent swimmers both on and underneath the surface. The methods of progression were similar to land movements; i. e., the limbs were employed differently at various times depending upon the speed. When first placed in water they moved rapidly by lunges produced by sweeping strokes of the hind limbs employed simultaneously. This movement was accomplished similarly to the long jumps made on land ... Following the first excited lunges, they settled down to a steadier and slower gait using all four limbs one at a time. The anterior part of the body was held high in the water ... When approached too closely, they attempted to escape by diving. The maximum distance noted was about four feet ... One was able to swim vigorously for approximately three minutes after which it tired greatly and was in danger of drowning."

As concerns digging ability, Goodwin (1935:148) reports that _Z. hudsonius_ makes its own burrows; these are short and close to the surface in the summer but longer, deeper, and below the frost-line in winter. Two captives used their forefeet and nails in digging a tunnel in the foot of soil that Goodwin (_loc. cit._) had placed in their cage. Quimby (1951:72) remarks that captives excavate soil by means of the front feet and throw the soil out behind; as the burrow deepened the hind feet were also utilized to throw the loose soil out of the burrow.

_Zapus hudsonius_ climbs; Sheldon (1934:293) observed captive animals to climb over small evergreen trees in their cages. They moved with surprising sureness and agility, chasing each other among the branches or sitting for several minutes at a time on one of the limbs. Hamilton (1935:190) found that the mice ran over limbs and brush which were placed in their outdoor enclosure.

Ordinarily _Z. hudsonius_ is nocturnal, appearing in the early dusk and remaining active until pre-dawn. Occasional individuals are abroad in daylight hours. Sheldon (1934:293) found in Nova Scotia that _Z. hudsonius_ is most active from early dusk through the night, but that it may be abroad in daylight as well. Her statements are based on trapping results, field observations, and observations made on captive individuals. Quimby (1951:73) found that _Z. hudsonius_ in Michigan is mostly nocturnal; however, he saw mice on a few occasions in the daytime. Diurnal activity seems to be increased in cloudy or damp weather; Quimby (_loc. cit._) almost invariably trapped more of these mice on cloudy, damp days than on other days.

This jumping mouse usually is silent but does utter various sounds. Sheldon (1934:295) records squeaking and clucking noises. Quimby (1951:73) records the clucking noise described by Sheldon (_loc. cit._) and mentions also the squeaking and suckling sounds produced by the small young. This mouse is most vociferous when young or when about to go into hibernation. Sheldon (1938:327) writes that _Z. hudsonius_ makes a drumming noise by vibrating the tail against dry leaves.

Many data are available concerning the hibernation of _Z. hudsonius_. In general it seems necessary for the mice to put on a certain amount of fat preparatory to hibernation. This fat is deposited in a thin layer over the inside of the skin, over the back, and in the body cavities. The thickest deposits are in and about the inguinal region.

Quimby (1951:83) noted that gain in weight was accelerated in a brief period prior to entrance into hibernation. This relationship of rapid gain in weight to hibernation allows a person to estimate the date of hibernation. Cold weather seems to hasten hibernation, but less so than the correct physiologic condition which is foreshadowed by a rapid gain in weight. For example, Quimby's (1951:84) data reveal that mice that were moved to a heated room gained weight and hibernated in a fashion similar to those in unheated surroundings. Hamilton (1935:193) states that, "It seems necessary for the mouse to lay on a certain amount of fat before it is capable of hibernation." Hamilton (_loc. cit._) reported that 18 specimens of _Z. hudsonius_ taken [presumably in an active state] near Ithaca, New York, on November 13, were without a trace of fat.

Data that are available concerning the hibernation sites of _Z. hudsonius_ show that almost invariably these mice seek shelter in burrows beneath the surface of the ground and there construct nests of grass, leaves, or some other vegetation. Nicholson (1937:103) found a hibernating _Z. hudsonius_ on the George Reserve, Livingston County, Michigan, on October 20. The mouse was in a nest, composed of 10 to 12 damp elm leaves, in a sand bank two feet three inches vertically and three feet nine inches horizontally from the surface. On April 11, 1948, Schwartz (1951:228) found five nests (three with occupants) of _Z. hudsonius_ at Jefferson City, Cole County, Missouri. All nests were one foot beneath the surface of a pile of coal-ash, which was about three and one-half feet high and five feet in diameter. The nests were spherical, approximately four inches in diameter and consisted of dried oak leaves and bits of dried grass. Grizzell (1949:74) found two hibernating jumping mice at the Patuxent Research Refuge, Laurel, Maryland, in January, 1948. The mice were in separate woodchuck dens; one mouse was 40 inches below the surface and the other was 26 inches below the surface. The mice were curled up in the center of masses of dead leaves, and thus, were well insulated against the cold. On April 29, 1944, at Ithaca, New York, Eadie (1949:307) uncovered a hibernating jumping mouse. The nest, about the size of a baseball, was compactly made of fine grasses and was 10 inches below the surface of the ground in a mound of earth that was approximately six by four feet at the base and three feet high.

From the foregoing reports on hibernation sites it is evident that well drained areas are utilized. Sheldon (1934:300) remarks that the burrows used for hibernating are dug in a bank or some place from which the rain water and melted snow probably drains off.

Eadie (1949:307), Grizzell (1949:75), Sheldon (1934:299), Schwartz (1951:228), and Sheldon (1938:331) all agree that the hibernating mouse rolls up into a ball-like shape (resting on its head and pelvis) with the head between the hind legs, the nose against the lower belly, the forefeet curled on the chest, and the tail curled around the head and body.

A marked loss of weight occurs immediately after hibernation begins, and then reduction in weight is slow and regular. (See Hamilton, 1935:194 and Quimby, 1951:84.)

Sheldon (1934:297) cites a letter from Vernon Bailey in which he remarks on the necessity of abundant moisture and saturate air for hibernating jumping mice. Bailey writes "... they will awaken at times famished for water and will drink and drink before going back to sleep."

Hamilton (1935:195) thinks that in the Ithaca area of New York these mice probably leave their winter quarters in the second half of April and that in southern New York and Long Island they emerge considerably earlier. Quimby (1951:82) and Bernard Bailey (1929:163) report that males appear earlier in the spring than do the females. Quimby (_loc. cit._), by recording the sequence and dates of phenological events and appearance of _Zapus_ in several years, was able to predict fairly accurately the time of emergence of _Zapus_ in a succeeding year. In Minnesota, jumping mice emerged late compared to other hibernating rodents.

_Enemies._--V. Bailey (1927:119) reports that A. K. Fisher found 50 skulls of _Zapus_ in barn owl pellets taken from the towers of the Smithsonian Institution, Washington, D. C. Dearborn (1932:32) reported mink as having fed on jumping mice. Surface (1906:197) records taking a _Zapus_ from the stomach of a rattlesnake. Pearson and Pearson (1947:138) found remains of _Z. hudsonius_ in pellets of barn owls. Quimby (1951:74) reports two cases of predation on _Z. hudsonius_; one was by a northern pike, _Esox lucius_ Linnaeus and the other was by a weasel, _Mustela_ sp. Vergeer (1948:91) collected a green frog, _Rana clamitans_ Latreille, which had eaten a jumping mouse.

Quimby (1951:74) frequently found the fleas, _Megabothris quirini_ Rothschild, and _Megabothris wagneri_ (Baker), and occasionally a larval tick, _Dermocenter variabilis_ (Say), on _Z. hudsonius_. Sheldon (1934:296) remarks that captive animals are burdened with numerous fleas. Hamilton (1935:191) removed a louse from a jumping mouse. One mouse had a hole in the throat and three others had holes in the inguinal region; presumably bot-flies had emerged from these holes. Test (1943:507) found a single _Cuterebra_ larva in the inguinal region of a _Z. hudsonius_, and Sheldon (1938:328) found _Z. hudsonius_ infested by larvae of _Cuterebra fontinella_ Clark. Here, as in other cases, these larvae were found immediately below the skin. Erickson (1938:252) examined 18 _Z. hudsonius_ obtained in Minnesota, and found that three were parasitized. He found a bot-fly larva, _Cuterebra_ sp., nematodes of the genera _Subulura_ and _Spirocerca_, and a fluke of the genus _Notocotylus_.

_Food._--Quimby (1951:85-86) studied the food preferences, by presenting to caged _Z. hudsonius_ the plants and invertebrate animals normally available to these mice in nature, and indicates that in general, the starchy fruits of the Gramineae and the less fleshy fruits of various groups of plants are more heavily utilized than other plant materials. His observations indicate that these rodents are highly insectivorous and that they consume many insects under natural conditions. Goodwin (1935:148) reports that the stomach contents of several individuals obtained at South Woodstock, Connecticut, consisted exclusively of blackberries, and that others had subsisted principally on cranberries. Hamilton (1935:197) remarks that seeds are the favored food but that berries, nuts, fruits of various kinds, roots, and insects are also utilized. Stoner (1918:123) writes that the food in cultivated areas of Iowa is various grains as well as grass and weed seeds; in wooded places the mice feed on seeds and nuts of trees. Vernon Bailey (1927:118) states that the examination of a great many stomachs of these jumping mice [in North Dakota] revealed nothing "but the fine white pulp of carefully shelled, well-masticated seeds. Generally these are from grasses, although grain and a variety of other plant seeds are eaten." Schmidt (1931:116) examined the stomach contents of several _Z. hudsonius_ taken in Clark County, Wisconsin, and in most stomachs found the remains of finely chewed roots; however, two from Hewett had eaten several geometrid caterpillars.

Lyon (1938:279), Stoner (1918:123), and J. W. Bailey (1946:263) present information which indicates that _Z. hudsonius_ stores food in its nests or burrows. Possibly these mice awaken at intervals from hibernation and eat.

"These rodents characteristically seize the material to be eaten with the front feet and devour it while reclining on their haunches. The following observation of a caged animal is typical of their feeding habits. The mouse selected a head of yellow foxtail, _Setaria glauca_ (Weig.) Stuntz, from several in the cage, separated it by gnawing through the supporting stem, seized it with the front feet, held it up to the mouth and began to gnaw at one end, stripping all parts from the rachis. The grass head was slowly rotated and shifted sideways until nothing remained but the rachis which was discarded. Actually the seeds were the only parts eaten ..." (Quimby, 1951:73). Sheldon (1934:294) remarks that _Z. hudsonius_ eats from a squatting position and holds the piece of food in the forepaws. The mouse seems to bite off a seed, and then, holding it in the forepaws, transfers it to the mouth.

According to Sheldon (_op. cit._:295) and Quimby (_loc. cit._), caged jumping mice drink water. When drinking, the mouths of the mice are in contact with the water, but neither observer determined whether the mice lapped or sucked the water. Sheldon (_loc. cit._) observed these mice passing stems of long grass through their mouths as though to squeeze out moisture, and thought that the mice obtain most of their required moisture from green plants.

_Reproduction._--The breeding season begins shortly after the jumping mice emerge from hibernation in the spring, and reproduction continues until a few weeks before they hibernate in the autumn. The extent of the breeding period probably varies geographically and possibly seasonally. For example, Quimby's (_op. cit._:70) information suggests that the 1947 period of parturition occurred between June 15 and August 30 in the area of Centerville, Minnesota. In Michigan, Blair (1940:246) found a peak of breeding activity in spring and another in late summer with little activity in the intervening midsummer. Brimley (1923:263) records a female in North Carolina, with eight embryos on June 13, 1895, and another with seven embryos on September 17, 1891, indicating a strong possibility of two litters per year there. Vernon Bailey (1927:118) records young born in May or June in North Dakota and thinks that there is time for only one litter per year. Petrides (1948:76) captured a female on September 22, 1944, at Athens, Georgia, that gave birth to six young on September 29. This late parturition date indicates a longer breeding season in the southeastern part of the range of _Z. hudsonius_.

The gestation period of nonlactating, caged _Z. hudsonius_, Quimby (1951:63) thinks, "is approximately 18 days ... [but] gestation is prolonged in lactating females."

Data from museum labels indicate that embryos in 62 pregnant females averaged 5.4 (2-8) per female. Quimby (1951:67) found the average number of embryos per female for 14 females taken in Minnesota, to be 5.3 and that litters of young found in nests averaged 5.8. Sheldon (1938:330) reports two litters of seven young each and one of four young for _Z. hudsonius_ in Vermont. Petrides (1948:76) records a litter of six young for _Z. hudsonius_ in Georgia. Brimley (1923:263) records one lot of seven and one lot of eight embryos for _Z. hudsonius_ in North Carolina. Vernon Bailey (1923:120) reports six embryos for a female of _Z. hudsonius_ taken in Washington, D. C. Ivor (1934:8) obtained a litter of five young _Z. hudsonius_ from Erindale, Peel County, Ontario. Hamilton (1935:195) records litters of two, four, and five young and embryo counts of four, two, four, and four for _Z. hudsonius_ in New York.

There seems to be two litters per year. According to Quimby (1951:69), "most adult females breed soon after emergence from hibernation and produce the first litters within a month. The remaining females do not breed immediately but produce the first litter," he says, "in the second month after emergence." Both early-breeding females and late-breeding females produce at least 2 litters per year. Those that breed early may have 3 litters.

The appearance and development of growing young of _Z. hudsonius_ in successive weeks is described by Quimby (1951:65). Newborn young are pink and hairless except for microscopic vibrissae. The eyes and external auditory meatus are closed, and the pinnae are folded. The toes are fleshy and clawless; the tail is short in relation to the length of the body. The average weight was .78 grams. The average measurements of three from different litters are: total length, 34 mm; tail, 9.2 mm; hind foot, 4.7 mm. The young are helpless but capable of emitting a high pitched squeaking sound which is audible for several feet.

In the first week of growth the vibrissae become visible to the naked eye, the body changes to flesh color, the dorsal parts become dark gray, the pinna unfolds and is black tipped, and the claws appear. The young now are able to crawl and make a suckling noise, but they are not yet able to support themselves on their legs.

In the second week of development, tawny yellow hair appears on the back and spreads onto the sides. Sparse hair of a lighter color appears on the belly, backs of the feet, and outer surfaces of the legs. Vibrissae are now prominent. The eyes are still closed, but a crack down the center of each is visible by the 13th day. Claws have grown, the longest measuring 1.5 mm. The incisors erupt on approximately the 13th day, those in the lower jaw appearing slightly before those in the upper jaw, and all are white. Activity is increased; nevertheless the young still crawl, make suckling notes, and squeak.

In the third week of development the mice are covered with hair; darker hair appears dorsally; and vibrissae continue rapid growth. The external auditory meatus begins to open on about the 19th day and young react to sound on the 20th. The incisors now are 1 mm long and the claws 1.5 mm long. Young are able to support themselves on their legs, walk, and make one inch hops.

In the fourth week the juvenal pelage is replaced by adult pelage. The eyes open between the 22nd and 25th days. The color of the incisors changes from white to yellowish-orange as in the adults. P^4, M^1, M^2, m1 and m2 have emerged from the maxillary and dentary bones; M^3 and m3 have not yet erupted. A mouse 33 days old had all teeth well developed. By the end of the 4th week the young, except for size, are adultlike and capable of independent existence.

The greatest increase in dimensions of the body is in the first four weeks. A slowing down of growth is simultaneous with weaning.

Other workers, Sheldon (1938:330), Petrides (1948:76), and Ivor (1934:8) also describe the appearance of the young.

Summer nesting sites are usually on the surface of the ground. Jumping mice characteristically construct a globular nest of grass but will utilize other vegetation if grasses are not available. Nests are usually concealed under rocks, logs, bushes, or grass and can be entered by a hole at one side.

Sheldon (1938:328) described a nest of _Z. hudsonius_ found on the ground near the edge of a small hay field. The nest was globular, not more than four inches in outside diameter and two inches in inside diameter; it was closely woven of fine, dry grass and bits of moss. Another nest found in the same field measured 11.5 inches in circumference at the base and six inches in circumference over the top. The inside width and length each was three inches, and the inside height was 3.5 inches. Vernon Bailey (1927:118) remarks that summer nests are placed on the surface of the ground well concealed under grass or other vegetation. He describes the nest as "neat little balls of fine grass with a tiny opening at one side and a soft lining in the central chamber." Cory (1912:249) reports that summer nests are concealed behind rocks or under bushes and thick grass. The nests are round and four or five inches in diameter with an entrance hole at one side. Goodwin (1935:148) examined a nest made entirely of straight, narrow leaves of grass. Ivor (1934:8) found one made of finely shredded jute sacking. Quimby (1951:80) describes several nests: one in the center of a rotten willow log was lined with small pieces of pulpy wood; another was in the rotted wood and debris, at ground level, inside a large, red oak (this globular nest composed of grasses, plant fibers, and rootlets measured six inches in diameter). Another nest was composed of a pile of wood pulp, leaves of oaks, and grasses; this nest was in a hollow root detached from a willow tree.

The mean home range of males, of _Z. hudsonius_ in Minnesota, according to Quimby (1951:86), was 2.70 plus or minus .50 acres; this was significantly larger than the mean home range of females, 1.57 plus or minus .27 acres. According to Quimby (_loc. cit._), the size and shape of the home range is influenced by the general features of the terrain, density and type of cover, and land use in the immediate area. Quimby (1951:94) remarked that the home range of the jumping mouse is relatively unstable and Blair (1940:247) stated that the home ranges of both sexes generally overlapped the ranges of other members of the same species and sex. The average size of the home range for _Z. hudsonius_ in Michigan was .89 plus or minus .11 acres for males and .92 plus or minus .11 acres for females.

=Zapus hudsonius acadicus= (Dawson)

_Meriones acadicus_ Dawson, Edinburgh New Philos. Jour., new ser., 3:2, 1856.

_Meriones labradorius_, Dawson, Edinburgh New Philos. Jour., new ser., 3:2, 1856.

_Jaculus hudsonius_, Baird, Rept. Expl. and Surv...., 8 (pt. 1):433, July 14, 1858 (part--the part from Nova Scotia, Vermont, and New York).

_Zapus hudsonius_, Coues, Bull. U. S. Geol. and Geog. surv. of the territories, 2nd ser., No. 5:260, 1877 (part--the part from Nova Scotia, Vermont, and New York); Preble, N. Amer. Fauna, 15:17, August 8, 1899 (part--the part from New Brunswick, Nova Scotia, Maine, New Hampshire, Vermont, Massachusetts, and northeastern New York).

_Zapus hudsonius canadensis_, Batchelder, Proc. New England Zool. Club, 1:5, February 8, 1899 (part--the part from Keene Valley in Essex County of New York, and Orivell in Vermont); Anderson, Ann. Rept. Provancher Soc. Nat. Hist., Quebec, 1941:35-37, July 14, 1942 (part--the part from the tip of the Gaspé Peninsula in Quebec, New Brunswick, Maine, New Hampshire, Vermont, and New York).

_Zapus hudsonius hardyi_, Batchelder, Proc. New England Zool. Club, 1:6, February 8, 1899, type from Mt. Desert Island, Hancock County, Maine; Bole and Moulthrop, Sci. Publ. Cleveland Mus. Nat. Hist., 5:165, September 11, 1947 (part--but excluding Pennsylvania and Ohio).

_Zapus hudsonius acadicus_, Anderson, Ann. Rept. Provancher Soc. Nat. Hist., Quebec, 1941:38, July 14, 1942.

_Type._--No type specimen designated. Subspecies characterized from specimens obtained in Nova Scotia.

_Range._--Gaspé Peninsula of Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Maine, New Hampshire, Vermont, Massachusetts, northern Connecticut and northeastern New York. See fig. 47. Zonal range: Transition and Canadian.

_Description._--Size medium; back from near Ochraceous-Tawny to near Yellow-Ocher with heavy admixture of black-tipped hair, the dorsal band distinct against color of sides; sides lighter than back and from near Cinnamon-Buff to near Ochraceous-Buff lined with black-tipped hair; lateral line usually faintly marked but sometimes distinct and clear Warm-Buff; underparts white, sometimes suffused with color of sides; tail distinctly bicolored, brownish-black above and yellowish-white to grayish-white below; ears dark, edged with color of sides; feet grayish-white above; pterygoid fossae relatively narrow; zygomata relatively long and broad; auditory bullae relatively narrow, usually with depression on anterior surface; mastoid region relatively narrow; inferior arm of zygomatic process of maxillary relatively narrow.

_Comparisons._--From _Zapus hudsonius canadensis_, _Z. h. acadicus_ differs in: Size averaging larger; upper parts usually less brownish and more ochraceous, sides and flanks being more ochraceous and less yellowish; zygomata relatively longer; pterygoid fossae relatively narrower; auditory bullae relatively narrower and usually with depression on anterior surface.

From _Zapus hudsonius americanus_, _Z. h. acadicus_ differs as follows: Size larger; color darker on upper parts, flanks duller (less ochraceous); underparts white, much less frequently suffused with color of sides; ears dark, usually without flecks of ochraceous; general appearance of pelage not so brightly colored; zygomata longer; condylobasal length greater; mastoid region relatively broader; bullae larger, more inflated and usually with depression on anterior surface; maxillary tooth-row relatively longer.

For comparison with _Zapus hudsonius ladas_ see account of that subspecies.

_Remarks._--Specimens from various localities in Nova Scotia, Prince Edward Island and New Brunswick are essentially similar. Anderson (1942:38) revived the name _Z. h. acadicus_ for jumping mice from these areas, correctly considering them to be distinct from _Z. h. canadensis_, the geographic race immediately to the west.

In the size and shape of the auditory bullae, length of the zygomata, breadth of the pterygoid fossae, and general color of the pelage the populations from Nova Scotia and New Brunswick are essentially indistinguishable from material of _Zapus hudsonius hardyi_ from Maine. Thus, _Z. h. hardyi_ must fall as a synonym of the earlier proposed name _Z. h. acadicus_.

Bole and Moulthrop (1942:165) applied the name _Z. h. hardyi_ (= _acadicus_) to the mice inhabiting a large area from coastal Maine and central New Hampshire through southern New England, New York, northwestern Pennsylvania, and northeastern Ohio. I agree with Bole and Moulthrop (_loc. cit._) that the population of _Zapus hudsonius_ from Maine, New Hampshire, west-central and northern New England are different from neighboring subspecies and are referable to _Z. h. acadicus_, but find that material from extreme southern Massachusetts, Connecticut, southern New York, northwestern Pennsylvania, and northeastern Ohio is best referred to _Zapus hudsonius americanus_ (see account of that subspecies).

Intergradation between _Z. h. americanus_ and _Z. h. acadicus_ is indicated by specimens from Berlin, Rensselaer County, New York. In color of ears, length of zygomata, and size and shape of the incisive foramina these specimens are more nearly like _Z. h. americanus_ but in size and shape of the auditory bullae, breadth of the mastoid region, and general appearance of the pelage they are more nearly like _Z. h. acadicus_ and are here referred to _acadicus_. Specimens from Glenville, Schenectady County, New York, are intermediate in cranial characters between _Z. h. americanus_ and _Z. h. acadicus_ but in color are best referred to the latter. Specimens from 1 mi. S Ayer, Worchester County, Massachusetts, are like _Z. h. americanus_ in their short zygomata, narrow mastoid region and suffusion of the underparts; nevertheless, in the shape of the auditory bullae, breadth of the pterygoid fossae, and greater condylobasal length the specimens are more nearly like _Z. h. acadicus_ which they are here considered to be. Animals from Essex and Wilmington, Essex County, Massachusetts, are like _Z. h. americanus_ in external size and in the size and shape of the auditory bullae; but they are more nearly like _Z. h. acadicus_ in most cranial characters and in the general color of the pelage and are here assigned to _Z. h. acadicus_.

Specimens from Keene Valley, Essex County, New York, considered by Batchelder (1899:4) to be _Z. h. canadensis_, are in color, length of the zygomata, and size and shape of the auditory bullae more nearly like _Z. h. acadicus_ to which subspecies they are here assigned. A specimen from Orwell, Addison County, Vermont, that Batchelder (_op. cit._:5) referred to _Z. h. canadensis_ is more nearly like _Z. h. acadicus_ in the shape of the auditory bullae, length of the zygomata, and color of the pelage, and is here referred to _Z. h. acadicus_. Specimens from western New Brunswick, referred to _Z. h. canadensis_ by Anderson (1942:37), are more nearly like _Z. h. acadicus_. Specimens from Ste. Anne des Monts, Gaspé Peninsula, Quebec, are intermediate between _Z. h. canadensis_ and _Z. h. acadicus_ in color and size and also in the shape of the auditory bullae but are best referred to _Z. h. acadicus_.

_Zapus hudsonius acadicus_ as here understood is a relatively wide-ranging subspecies. Populations at the southern periphery of its range are difficult to separate from populations at the northern periphery of the range of _Z. h. americanus_. These two geographic races represent opposite extremes of a clinal gradient and, as would be expected, geographic intermediates are morphologically similar.

_Specimens examined._--Total, 156, distributed as follows:

MAINE: _Aroostock County_: _Madawaska_, 6 (MCZ). _Hancock County_: _Mount Desert Island_, 9 (6 MCZ, 3 UM). _Piscataquis County_: _Mount Katahdin_, 1 (USNM); Sebec Lake, 4 (USBS); _Katahdin Lake_, 1 (USBS). _Sagadahoc Co._: Small Point Beach, 1 (Clev. MNH). _Somerset County_: east branch Penobscot River, 2 (USBS). _Washington County_: Columbia Falls, 1 (USBS).

MASSACHUSETTS: _Essex County_: _Essex_, 4 (Clev. MNH); Wilmington, 4 (3 USBS, 1 USNM). _Worchester County_: _Lunenberg_, 2 (USBS); _1 mi. S Ayer_, 2 (MVZ); 2 mi. N Gilbertville, 1.

NEW BRUNSWICK: _Charlotte County_: _6 mi. N St. Andrews_, 2 (NMC); 5 mi. N St. Andrews, 4 (NMC). _Carleton County_: _Debec_, 1 (MVZ). _Gloucester County_: Dalhousie, 2 (MVZ); _Miramichi Road, 15 mi. from Bathurst_, 4 (NMC); _Youghall_, 3 (NMC). _Madawaska County_: Baker Lake, 2 (NMC); _9 mi. NE Edmundston_, 4 (NMC); 5 mi. N St. Leonard, 5 (NMC). _Victoria Co._: _Tobique Point_, 1 (AMNH). _York County_: _Queensbury_, 1 (USBS).

NEW HAMPSHIRE: _Carroll County_: _Intervale_, 1 (UM); _Ossipee_, 4 (3 USBS); _2 mi. S Ossipee_, 12 (2 USNM). _Coos County_: _Nathan Pond_, 1 (UM); Fabyans-Bretton Woods, Dartmouth Brook, 2 (UM); _Fabyans_, 1 (USNM); _3 mi. W Base Station_, 1; _Mt. Washington_, 1 (MVZ); _Pinkham Notch, 1900 ft._, 1 (USNM). _Grafton County_: _Franconia Notch, Profile Lake_, 1 (UM); Lebanon, 3 (UM). _Strafford Co._: _1 mi. E Durham_, 1 (UM).

NEW YORK: _Essex Co._: Keene Valley, 5 (MCZ); _Keene Heights_, 5 (MCZ); _Minerva, 1700 ft._, 1 (AMNH). _Herkimer County_: Northwood, 7 (AMNH). _Rensselaer Co._: Berlin, 8 (AMNH). _Schenectady County_: _Glenville_, 1 (USBS). _Warren County_: _Lake George_, 5 (USBS). _Washington County_: _Patterns Mills_, 1 (USBS).

NOVA SCOTIA: _Annapolis Co._: Bear River, 7 (NMC); _Lake Kedgemakooge_, 5 (UM); 2 mi. S Milford, 1 (AMNH). _Kings Co._: Black River Dist., 1 (NMC); _no exact locality_, 1 (NMC). _Shelburne County_: Doctors Cove, N Barrington Passage, 1 (NMC); _Barrington Passage_, 4 (NMC).

PRINCE EDWARD ISLAND: no exact locality, 1 (USBS).

QUEBEC: Ste. Anne des Monts, 1 (AMNH).

VERMONT: _Addison County_: Orwell, 1 (MCZ); _Lamville County_: Mt. Mansfield, 2 (USBS). _Windham County_: _Whitingham_, 2 (AMNH).

_Marginal records._--Quebec: Ste. Anne des Monts. New Brunswick: Dalhousie. Prince Edward Island. Nova Scotia: Black River District; Doctors Cove, N Barrington Passage. Maine: Columbia Falls; Small Point Beach. Massachusetts: Wilmington; 2 mi. N Gilbertville. New York: Berlin; North Wood; Keene Valley. Maine: E branch Penobscot River. New Brunswick: Baker Lake.

=Zapus hudsonius alascensis= Merriam

_Zapus hudsonius alascensis_ Merriam, Proc. Biol. Soc. Washington, 2:223, July 15, 1897.

_Zapus hudsonius hudsonius_, Osgood, N. Amer. Fauna, 24:37, November 23, 1904.

_Type._--Male, adult, skin and skull, No. 73584, U. S. Nat. Mus., Biol. Surv. Coll.; Yakutat Bay, Alaska; obtained on July 5, 1895, by Clark P. Streator, original No. 4660.

_Range._--Alaska Peninsula, coastal section of mainland of southern and southeastern Alaska including Revillagigedo Island; also southwestern Yukon. See fig. 47. Zonal range: Canadian and Hudsonian.

_Description._--Size large; back from near Ochraceous-Tawny to near Dresden Brown, sometimes darkened with black tipped hair usually with darker mid-dorsal area forming a band; sides lighter than back and from near Ochraceous-Tawny to near Clay Color; lateral line usually distinct, of clear Ochraceous-Buff; belly white, frequently with a slight suffusion of Ochraceous-Buff; tail bicolored, brownish to brownish-black above, white to yellowish-white below; ears dark, edged and flecked on the inner surface with color of sides; feet grayish-white above; auditory bullae broad and moderately inflated; pterygoid fossae relatively broad; incisive foramina relatively long, zygomata relatively long and broadly bowed; mastoid region relatively broad; distance from incisors to postpalatal notch relatively great; occipitonasal length relatively great.

_Comparisons._--From _Zapus hudsonius tenellus_, _Z. h. alascensis_ differs as follows: Size larger; upper parts darker, less ochraceous; sides duller, less ochraceous more tawny; incisive foramina averaging longer; mastoid region broader; occipitonasal length greater; zygomata wider-spreading and longer; condylobasal length averaging greater; auditory bullae less broadly rounded; and distance from incisors to postpalatal notch averaging greater.

For comparison with _Zapus hudsonius hudsonius_ see account of that subspecies.

_Remarks._--_Zapus hudsonius alascensis_ is a fairly well marked subspecies retaining most of its characters throughout its range. Variation is noted in specimens from the southwest end of Dezadeash Lake, 2400 ft., Yukon Territory, and seems to be the result of intergradation between _Zapus hudsonius hudsonius_ and _Z. h. alascensis_. These animals are like _Z. h. hudsonius_ in the shape of the auditory bullae but are otherwise more nearly like _Z. h. alascensis_ to which they are here assigned. Alaskan specimens from 7 mi. SSE Haines, and from a point 9 mi. W and 4 mi. N Haines average slightly larger than _Z. h. alascensis_ in most measurements taken; however, in coloration they more nearly agree with _Z. h. alascensis_ than with _Z. h. hudsonius_ or _Z. h. tenellus_ the geographic ranges of which adjoin that of _Z. h. alascensis_.

_Specimens examined._--Total, 56, distributed as follows:

ALASKA: Cook Inlet, Tyonek, 1 (USBS); head Chalitna River, 2 (USBS); Lake Clark, 4 (USBS); east side Chilkat River, 100 ft., 9 mi. W and 4