Volume 13, No. 10, pp. 429-611, pls. 31-54, 24 figs.

Published February 16, 1962

UNIVERSITY OF KANSAS

Lawrence, Kansas

PRINTED IN

THE STATE PRINTING PLANT

TOPEKA, KANSAS

1962

28-7818

North American Recent Soft-shelled Turtles

(Family Trionychidae)

BY

ROBERT G. WEBB

CONTENTS

PAGE

CONTENTS 431

INTRODUCTION 433 Collecting Methods 434 Materials and Procedure 437 Acknowledgments 439

TAXONOMY 439 Family Trionychidae Bell, 1828 439 Genus _Trionyx_ Geoffroy, 1809 443 Variation 445 Secondary Sexual Variation 446 Ontogenetic Variation 449 Geographic Variation 453 Character Analysis 460 Composition of the Genus _Trionyx_ in North America 476 Artificial Key to North American Species and Subspecies of the Genus _Trionyx_ 476 Systematic Account of Species and Subspecies 479 _Trionyx ferox_ 479 _Trionyx spinifer_ 486 _Trionyx spinifer spinifer_ 489 _Trionyx spinifer hartwegi_ 497 _Trionyx spinifer asper_ 502 _Trionyx spinifer emoryi_ 510 _Trionyx spinifer guadalupensis_ 517 _Trionyx spinifer pallidus_ 522 _Trionyx ater_ 528 _Trionyx muticus_ 531 _Trionyx muticus muticus_ 534 _Trionyx muticus calvatus_ 539

NATURAL HISTORY 541 Habitat 541 Daily and Seasonal Activity 547 Diurnal Habits 547 Behavior Adaptations 549 Movement 552 Nocturnal Habits 553 Seasonal Occurrence 553 Food Habits 555 Reproduction 558 Size of Males at Sexual Maturity 558 Size of Females at Sexual Maturity 560 Sexual Activity 563 Deposition of Eggs 565 Reproductive Potential 568 Eggs 572 Incubation and Hatching 573 Age and Growth 574 Mortality 576 Parasites 576 Economic Importance 577

EVOLUTIONARY HISTORY 578 Distribution 578 Relationships 579 Fossils 582 Phylogeny 585 The Importance of the Study of Turtle Populations in Relation to the History of River Systems 588

SUMMARY 590

LITERATURE CITED 594

INTRODUCTION

Is it true that the greater the degree of resemblance between two populations the shorter the time the two have been spatially isolated? Are aquatic environments more stable than terrestrial environments? These questions occurred to me while I was collecting turtles from river systems of the Gulf Coast. As a general rule, each kind of turtle seemed to occur throughout one continuous river system or large tributary, and with no barriers to dispersal therein and with the lapse of enough time for a population to reach its limits of dispersal, the question arose, "Where do subspecies and zones of intergradation occur?" It seemed logical to think that each isolated and continuous aquatic environment would not contain more than one subspecies of the same species. In terrestrial environments subspecies and transitions between them were recognizable. Terrestrial habitats were continuous for longer distances than the isolated, aquatic habitats. But, different species of turtles prefer different kinds of aquatic habitats. Also, barriers occur in large drainage systems, such as the Mississippi, where, in general, the western tributaries are sluggish, turbid and shallow, and the eastern tributaries are fast-flowing, clear and deep. But in young, relatively small, river systems that do not traverse radically different physiographic regions, and that show no gross ecological differences, habitats or microhabitats that do exist probably are only partial barriers and seem not to prevent the dispersal of most kinds of aquatic turtles. Consequently, it seemed that study of the degree of difference between closely related populations of turtles that occurred in one drainage system, or in adjacent drainage systems would indicate the length of time, respectively, that the drainage system had been continuous or the length of time that two or more systems had been isolated from one another.

Rivers or series of river systems having endemic kinds of turtles or having the most kinds of turtles that are different from those in adjacent rivers may be the oldest geologically, or may have been isolated the longest. Knowledge of the kinds of turtles and their relationships and distribution could indicate chronological changes in aquatic habitats. Of course, modifying factors such as differences between populations of turtles in rates of evolutionary change, degrees of vagility, rates of dispersal, and overland migrations need to be taken into account.

My accumulation of data on soft-shelled turtles was begun in the early nineteen-fifties. Although American softshells have been discussed in a revisionary manner by Agassiz (1857), Siebenrock (1924), Stejneger (1944) and Neill (1951), the relationships of all the component populations have not hitherto been appreciated. The present account attempts to combine in one publication what is known concerning the taxonomy, geographic distribution, life history, and relationships of the Recent American species and subspecies of the genus _Trionyx_.

Collecting Methods

Nocturnal collecting, by hand, from a boat that was nosed among brush piles along the shore line of rivers (Chaney and Smith, 1950:323) in the early 1950's on rivers of the Gulf Coast drainage east of Texas yielded many turtles of the genus _Graptemys_ but few softshells. Chaney and Smith (_loc. cit._) reported only one softshell among 336 turtles taken in 21 collecting hours on July 5, 6 and 7 on the Sabine River; Cagle and Chaney (1950:385), however, recorded 11.6 per cent softshells of 208 turtles (collecting time not stated) taken on the Caddo Lake Spillway in Louisiana. Using hoop-nets is probably the most efficient method for collecting softshells considering the time and effort involved, and is the chief method I have used. Lagler (1943a:24) mentioned the use of watermelon rind as an effective bait. Kenneth Shain (field notes) trapped _T. spinifer emoryi_ in hoop-nets baited with bread. I have used chopped fresh fish with most success; canned sardines have also been satisfactory. These baits seem to be more successful for trapping _spinifer_ than they are for _muticus_. Hoop-nets were used to trap turtles in Lake Texoma, Oklahoma, from June 14 to July 2, 1954. The number of traps (usually four, rarely five) and trapping success varied with location. Of 156 turtles, 19 (12%) were _T. spinifer_ and one was _T. muticus_.

Trotlines and set lines frequently catch softshells; sport fishermen often complain of catching these turtles on hook and line. Live worms, soft-bodied insects, small crawfish, minnows, small pieces of fish and other kinds of meat are adequate bait. Capture depends on the skill of attachment of the bait and the size of hook used. In my experience, softshells (mostly _spinifer_) were taken on trotlines that were set in lakes or the slower-moving parts of rivers a few inches below the surface. I have records of only two _muticus_ taken on trotlines. Goin (1948:304) stated that commercial fishermen catch softshells on trotlines set for catfish on the bottom of river beds. Evermann and Clark (1920:595) found softshells to be caught more often than any other kind of turtle in traps, on set lines, and by anglers in Lake Maxinkuckee, Indiana. Some residents of the South tell of so placing baits that turtles are lured to tread water against an object set with recurved hooks upon which the webbing of the forelimbs are impaled.

Individuals of _muticus_ and _spinifer_ frequently bury themselves in sand in shallow water and can be collected by hand by noting swirls or disturbances on the bottom caused by a turtle withdrawing its head (Conant, 1951:156, 159). Professional turtle collectors take them by "noodeling" (Conant, _op. cit._:160); Lagler (1943a:22) elaborated on the method of "noodling." P. W. Smith (1947:39) remarked that 20 or more softshells were taken "within a few hours by probing sand bars at the water edge" near Charleston, Illinois. From a distance I observed an individual of _T. s. asper_ bury itself in shallow water on the Escambia River, Florida. Small individuals of _muticus_ have been taken by hand along the shore of Lake Texoma. Along the Flint River near Bainbridge, Georgia, two hatchlings that were buried in sand in shallow water emerged at my approach and scurried a few inches, then buried themselves again. Larger turtles seem to be more wary. One that was disturbed, emerged from the sand and swam toward deep water.

In clear water, water-goggling may be effective in securing softshells. Marchand (_in_ Carr, 1952:417-18) mentioned that softshells (_ferox_) can be found buried in deep water with only the heads visible; the turtles are not easily frightened under water and may be captured by grasping their necks. A similar technique described by Allen and Neill (1950:3) resulted in the capture of trionychid turtles. In clear water of the White River, Arkansas, I collected a few softshells by hand as they lay on the bottom.

In shallow-water areas of large rivers, lakes and tributaries, seining often procures softshells. Methods used in fisheries investigations such as the application of rotenone and electric shockers, and even dynamiting, sometimes yield soft-shelled turtles. Carr (1952:419) wrote that numbers of _ferox_ were incapacitated by rotenone in Florida lakes, although no other species of turtle was affected. I captured a snapping turtle (_Chelydra serpentina_) that was immobilized by the current from an electric shocker in a small, alga-choked tributary of Cache Creek, Comanche County, Oklahoma; presumably turtles must come in close contact with the electrodes to be affected (see discussion by Gunning and Lewis, 1957:52).

The effectiveness of gill nets in trapping turtles is indicated by information kindly supplied by Mr. Alfred Houser on gill-net operations from July through December, 1952, under the direction of Mr. "Bud" Oldham, a commercial fisherman. The 4-inch mesh nets were in Lake Texoma at the mouth of Briar Creek, two miles south of Powell, Marshall County, Oklahoma, in 25 to 30 feet of water. Eighty to 90 per cent of the turtles secured were softshells; more were taken near shoreline than away from shore even though the depth was about the same. An average of only one turtle every four days was taken in July and August when the turtles presumably are most active (Table 1). One gill-net day is equivalent to one gill net, 200 yards long, operated for 24 hours.

TABLE 1. The Abundance of Turtles as Revealed by Gill-net Operations in Lake Texoma, 1952.

===========+==========+===========+=============== | Gill-net | Number of | Gill-net days MONTH | days | turtles | per turtle -----------+----------+-----------+--------------- July | 835 | 213 | 3.9 August | 816 | 199 | 4.6 September | 743 | 42 | 17.7 October | 1661 | 82 | 20.3 November | 1322 | 48 | 27.5 December | 864 | 5 | 172.8 -----------+----------+-----------+---------------

Dr. Virgil Dowell, while making fishery studies two miles east of Willis, Marshall County, Oklahoma, caught, on the average, 1.5 turtles per day. Of 75 turtles collected from July 1 through October 18, 1953, 66 were _Trionyx_ (_spinifer_ and _muticus_), five were _Graptemys_ and four were _Pseudemys scripta_. No more than two gill nets were used simultaneously. The nets were moved from time to time and varied in dimensions, but those used most of the time were 200 feet long and eight feet deep with a 3-inch mesh.

The few captures by Houser probably resulted from long-continued trapping in one place; the gill nets were not moved in the entire six-month period or for some time previously. Breckenridge (1955:6) commented on the sedentary nature of _spinifer_ (in Minnesota) and quoted a professional turtle trapper as stating that "after a section of a river has been trapped heavily for softshells, little success can be expected in that area for as much as three or four years thereafter." Both Houser's and Dowell's data indicate a higher percentage of soft-shelled turtles collected than any other species. The number caught probably depends, at least partly, on the food habits of the species and is influenced by the enmeshed fish, which, serving as a food source, attract the turtles.

Materials and Procedures

In the course of this study I examined 1849 soft-shelled turtles, including some incomplete alcoholic or dried specimens, such as those represented only by skulls or by other osteological material. Material was examined from each of the collections named below (except KKA), and these are mentioned in the text by the following abbreviations:

AMNH American Museum of Natural History ANSP Academy of Natural Sciences, Philadelphia BCB Bryce C. Brown, private collection, Baylor University CM Carnegie Museum CNHM Chicago Natural History Museum INHS Illinois Natural History Survey, University of Illinois KKA Kraig K. Adler, private collection, data in letter dated January 8, 1960 KU Museum of Natural History, The University of Kansas LSU Louisiana State University MCZ Museum of Comparative Zoology, Harvard College MSU The Museum, Michigan State University NHB Naturhistorisches Museum Basel, Switzerland OU University of Oklahoma Museum, Division of Zoology SM Strecker Museum, Baylor University TCWC Texas Cooperative Wildlife Collection, Texas Agricultural and Mechanical College TNHC Texas Natural History Collection, The University of Texas TTC Texas Technological College TU Tulane University UA University of Alabama UI Museum of Natural History, The University of Illinois UMMZ Museum of Zoology, The University of Michigan USNM United States National Museum WEB William E. Brode, private collection, Mississippi Southern College WTN Wilfred T. Neill, private collection

External measurements (listed under the section, "Variation") were taken by the writer by means of a Vernier caliper or a steel tape. Measurements of the skulls are in millimeters and tenths as taken by the writer with dial calipers. Partial wrinkling of the carapace at the edges of some specimens causes some error in measurements; consequently, length of plastron is used as the measurement of reference.

Scattergrams based on external measurements were constructed. Some demonstrate considerable ontogenetic variation. An inspection of the scattergrams indicated regressions essentially linear in nature, but sometimes occasioned an arbitrary separation of samples into size groups to show ontogenetic variation; no secondary sexual differences could be discerned. Several ratios were developed from the measurements. The data correspond to the regression model 1A in "Statistical Methods" (Snedecor, 1956, sec. 6.13); consequently, the sample ratios indicate the slope of regression and are useful in comparisons. Sample-means and their estimated standard errors are compared graphically to show general trends in proportional characters. Comparisons of means and standard errors indicate statistical significance between populations if the sample-means plus or minus twice their standard errors do not overlap, but this method of comparison is valid only when comparing two samples (Pimentel, 1959:100).

In the section on "Variation," general features applicable to all kinds of soft-shelled turtles are discussed under the following headings: secondary sexual, ontogenetic, and geographic; individual variation is mentioned in accounts of species and subspecies. In the section "Character Analysis" external and osteological characters having taxonomic significance are discussed.

Vernacular names follow, as closely as possible, those recommended by the Committee on Herpetological Common Names (1956). The synonymy of each monotypic species or subspecies begins with the name as given in the original description. The second entry is the name-combination herein applied to the taxon. Other entries are first usages, in chronological order, of other names (synonyms) that have been applied to the taxon in question. Next, the type is briefly discussed followed by the "Range" defined in general geographic terms, and, when appropriate, in terms of river drainage systems. "Diagnosis" includes a combination of characters that facilitates quick identification. In polytypic species, the diagnosis of a subspecies is designed only to distinguish it from other subspecies of that species. The comments included under the subsection entitled "Description" pertain to individuals from an area where the taxon is most clearly differentiated. Because osteological characters are significant only at the specific level, they appear under the accounts of each species (excluding _ater_). Proportional characters as given in the "Diagnosis" are only in general terms; more specific data are set forth in the subsection, "Description" or in the various text figures, mostly in the section on "Variation," page 445. Proportions pertaining to the species _muticus_ were derived only from the nominal subspecies, and appear under the account of the species. A subsection "Variation" under the accounts of some subspecies includes information concerning principally individual variation and coloration; because color is not considered to be of major taxonomic importance, color terms are used without reference to any standard color guide. The subsection "Remarks" follows the section on "Comparisons," and may include comments on nomenclature, intergradation and other information related to the distribution or taxonomy of the subspecies.

The probable geographic range of each species and subspecies is shown on one of the maps. Locality records of specimens that I have examined are shown by solid circles. Additional records of occurrence (published records or specimens otherwise not seen) are shown by hollow circles. Localities only a short distance apart share the same circle.

Under the subsection "Specimens examined," a number in parentheses following a museum number indicates the number of specimens referable to that museum number. All localities of specimens examined are indicated on one of the maps. The list of specimens is arranged alphabetically by states (Canadian provinces precede states of the United States under the account of _T. spinifer spinifer_, and Mexican states follow those of the United States under _T. s. emoryi_), alphabetically by counties, and within a county alphabetically by abbreviations of museums; then, museum catalogue numbers are arranged consecutively. Records in the literature are not included if they refer to the same locality from which at least one specimen has been examined, or refer to a less restricted locality that includes the area from which at least one specimen has been examined. Localities within a county are arranged alphabetically by author; the appropriate reference may follow several localities.

All generic, specific and subspecific names (but not all the different kinds of name-combinations) that have been applied to American soft-shelled turtles are listed in a subsection entitled "Synonymy" under the heading "Genus Trionyx Geoffroy, 1809."

Acknowledgments

Completion of this study has been made possible only by the co-operation of those persons in charge of the collections listed above and I am grateful to them for the privilege of examining specimens. Also I wish to thank Dr. E. Raymond Hall for the facilities afforded by the Museum of Natural History at the University of Kansas, as well as for editorial assistance in the preparation of the manuscript, and especially Dr. Henry S. Fitch under whose guidance this research was carried out.

In addition to various staff members, graduate students, and individuals whose help is acknowledged at appropriate places in the text, Dr. Rollin H. Baker, Dr. Fred R. Cagle, Mr. J. Keever Greer, Dr. A. Byron Leonard, Dr. Carl D. Riggs, and Dr. Edward H. Taylor deserve especial mention for aid extended in the course of this study. I am indebted to Mr. J. C. Battersby, British Museum (Natural History), London, for information concerning the type of _Trionyx ferox_, to Dr. Jean Guibé, Museum d'Histoire Naturelle, Paris, for information concerning the types of _Trionyx muticus_, _T. spinifer_ and _T. carinatus_, and photographs of the types of _T. muticus_, _T. spinifer_ and _T. ocellatus_, and to Dr. Lothar Forcart of the Naturhistorisches Museum, Basel, Switzerland, for information pertaining to a published record of _T. muticus_.

The maps and figures are the work of Miss Lucy Jean Remple and Mrs. Lorna Cordonnier, University of Kansas. Dr. John M. Legler, University of Utah, prepared most of the photographs on plates 1-20; photographs as mentioned in the preceding paragraph were received from Dr. Guibé, one was provided through the co-operation of Roger Conant and Isabelle Hunt Conant, another was furnished by Mr. J. Keever Greer, and the others were taken by me. Field work was financed in part by funds provided by the Sigma Xi-RESA Research Fund.

TAXONOMY

Family Trionychidae Bell, 1828

Recent soft-shelled turtles comprise a well-defined assemblage of the family Trionychidae. Although the scope of this study does not involve an assay of the relationships of the soft-shelled turtles of the Old World, a brief résumé that includes some of the salient characteristics of the family is included.

_Diagnosis._--Articulation between last cervical and first dorsal vertebrae by zygopophyses only; preplastra separated from hyoplastra by /\-shaped epiplastron, entoplastron absent (Williams and McDowell, 1952:263-75); marginal bones absent or forming an incomplete series, not connected with ribs that extend beyond pleural plates; claws on only three inner digits; fourth digit having four or more phalanges; plastron united to carapace by ligamentous tissue (Smith, 1931:147).

_General characters._--Size large, "... some attaining probably 5 feet in length of carapace" (Boulenger, 1890:10); body depressed; carapace and plastron lacking horny epidermal shields, covered instead with soft skin; snout ending in fleshy, tubate proboscis; jaws concealed by fleshy lips; tail short; digits well-webbed; cervical vertebrae opisthocoelous (eighth having double articulation in front); neck elongate, cervical region equaling or exceeding length of dorsal vertebral column; head and neck completely retractile, bending by means of sigmoid curve in vertical plane; ear hidden; skull elongate, having three posterior projections (median one produced by supraoccipital and two lateral projections formed chiefly by squamosals); temporal region emarginate posteriorly, forming wide shallow fossa; premaxillae fused; an intermaxillary foramen; pterygoids separated by basisphenoid that contacts palatines; vomer, if present, not separating palatines; pelvis not fused to carapace and plastron; plastron reduced, a median vacuity usually present; plastral bones developing sculpturing with increase in size, forming four to seven so-called plastral callosities; carapace with or without prenuchal bone; nuchal overlapping or overlapped by first pleural; neurals in continuous series or interrupted by pleurals; bony plates of carapace sculptured; mandible having well-developed coronoid bone; cutaneous femoral valves that conceal hind limbs present or absent; two or three pairs of scent glands; cloacal bursae absent (Smith and James, 1958:89); forelimbs having antebrachial scalation; body of hyoid apparatus formed of two or three pairs of bones; penis broad, expanded and pentifid, sulcus spermaticus quadrifid having branches in each of four lateral projections (Hoffman, 1890:298, pl. 47, fig. 2); aquatic, principally in fresh water; mainly carnivorous; flesh of many species eaten. (See Boulenger, 1889:237-41; Loveridge and Williams, 1957:412; Romer, 1956:513; Smith, _op. cit._:147-54).

_Recent distribution_ (Figure 1).--North America, from extreme southeastern Canada and eastern United States west to Rocky Mountains and south to northern México; introduced in southwestern United States (Conant, 1958:69-73). Africa, from Egypt and Senegal south to Angola and Zambesi River drainage (Loveridge and Williams, _op. cit._:412-68); occurrence of _Trionyx triunguis_ in Syria (Boulenger, _op. cit._:255) and coastal streams of Palestine (Schmidt and Inger, 1957:36) considered accidental by Flower (1933:753-54). Southwestern Asia (Tigris and Euphrates River drainage) in eastern Turkey, Syria, Iraq and northeastern Israel (Mertens and Wermuth, 1955:388). Southeastern Asia, from Pakistan and India (Indus River drainage) and Manchuria and adjacent Siberia (Amur River drainage) to Ceylon, Japan, Formosa, Hainan, Luzon, Sumatra, Java, Borneo, Timor and southeastern New Guinea (De Rooij, 1915:325-32; Okada, 1938:108; Pope, 1935:60-64; Smith, 1931:158-79; Stejneger, 1907:514-532; Taylor, 1920:141).

_Trionyx cartilagineus_ is questionably recorded from the Moluccas (De Rooij, _op. cit._:330). _T. sinensis_ has been introduced on Kauai Island, Hawaiian Islands (Brock, 1947:142; Oliver and Shaw, 1953:83), one of the Bonin Islands (Okada, 1930:187-94), and probably Timor (De Rooij, _op. cit._:331). All insular records east of Borneo and Java are probably the result of introductions, except perhaps those of _Pelochelys_ on Luzon and New Guinea (Darlington, 1957:210).

_Recent genera._--According to Mertens and Wermuth (1955:387-95), there are 21 species belonging to six genera as follows:

_Chitra_ Gray, 1844 (1) _Cyclanorbis_ Gray, 1854 (2) _Cycloderma_ Peters, 1854 (2) _Lissemys_ Smith, 1931 (1) _Pelochelys_ Gray, 1864 (1) _Trionyx_ Geoffroy, 1809 (14)

_Dogania_ is considered a synonym of _Trionyx_ (Loveridge and Williams, _op. cit._:422).

_Geologic range._--Lower Cretaceous (possibly Upper Jurassic) to Recent of Asia; Upper Cretaceous to Recent of North America; Paleocene (Upper Jurassic, assuming _Trionyx primoevus_ is a trionychid) to Pleistocene of Europe; Lower Miocene to Recent of Africa; Pleistocene to Recent in East Indies (Loveridge and Williams, _op. cit._:412; Romer, 1945:594); questionable trionychid fragments from Pleistocene of Australia (Darlington, _loc. cit._). $/

_Remarks._--The genera _Lissemys_, _Cyclanorbis_ and _Cycloderma_ are distinguished from _Pelochelys_, _Chitra_ and _Trionyx_ by several characters (Loveridge and Williams, _op. cit._:414). The recognition of two groups of genera caused Deraniyagala (1939:290) to erect two families, Cyclanorbidae and Trionychidae. An appraisal of fossils prompted Hummel (1929:768) to propose two corresponding subfamilies, Cyclanorbinae and Trionychinae. Williams (1950:554) considered the two groups as subfamilies (Lissemydinae and Trionychinae).

Baur (1887:97) regarded the Trionychidae as constituting a separate suborder distinct from the rest of the living turtles. Later (1891), however, he pointed out the resemblances of the Trionychidae and Carettochelyidae (having one living genus in New Guinea), and the cryptodiran affinities of _Carettochelys_. Bergounioux (1932:1408) mentioned the close resemblance of the Carettochelyidae to _Trionyx_ but considered the former as having pleurodiran affinities, a view adopted by Deraniyagala (_loc. cit._). Most students now consider the two families to be closely related, and conceive of both as members of the suborder Cryptodira (Hummel, 1929:768; Williams, _loc. cit._; Mertens and Wermuth, 1955).

The oldest trionychid fossil, _Trionyx primoevus_, is from marine deposits of the Upper Jurassic (Kiméridgien) from "Cap de la Hève," and its characters do not indicate the kind of cryptodiran ancestor from which the family arose (Bergounioux, _op. cit._:1409; 1937:188). Lane (1910:350) found that the entoplastron (= epiplastron) was paired in embryos of _Trionyx_ and regarded that genus as the most primitive of the order; he also mentioned Wiedersheim's report of rudiments of teeth in embryos of _Trionyx_. Baur (1891:637-38) thought that the family arose directly from the Amphichelydia, that the ancestors of the Trionychidae closely resembled _Carettochelys_ in the structure of the carapace and plastron, and that a progressive reduction in ossification of those structures occurred. Nopcsa (1926:654) also wrote that the family originated from ancestors having a well-developed plastron; he maintained that the progressive reduction in ossification of the plastron was a specialization for aquatic life, and that the more primitive trionychids had the best developed bones and callosities. Hummel (1929:772) also thought that there had been a progressive reduction in ossification. Bergounioux (1932:1408; 1936:1088, 1952:2304), on the contrary, thought that there had been a progressive increase in ossification of the marginal bones in both families as well as of the plastron (1936:1088; 1937:190). Zangerl's study of the shell elements of turtles (1939:393) indicated that _Trionyx_ was highly specialized in having a well-developed epithecal armor (sculptured callosities, neurals and costals), and that it occurred in most aquatic turtles; the development in soft-shells suggested that members of the family had maintained an aquatic mode of life over a long period of geologic time, a view supported by Deraniyagala (1930:1066). Of interest are Stunkard's remarks (1930:214-18) concerning several _Trionyx spinifer_ that were obtained from a commercial supply house and found to be infested with pronocephalid trematodes (_Opisthoporus_ [= _Teloporia_] _aspidonectes_). The closest relatives of that trematode (also recorded from _T. ferox_) live in marine turtles. Possibly, a Mesozoic ancestor of marine and essentially fresh-water soft-shelled turtles harboured ancestors of these trematodes, but possibly the parasites may have transferred relatively recently to their present hosts. Bergounioux (1937:190) judged the Trionychidae to be an ancient group of marine origin. Hummel (1929:770) wrote that the Trionychidae originated in east Asia (the region of most differentiation) in humid climates.

Baur (1891:634, 637) pointed out that the dorsal aspect of the skull of the closely related _Carettochelys_ resembles the skull of the Dermatemydidae, Staurotypidae and Kinosternidae; the close relationship of _Carettochelys_ and the Dermatemydidae is also mentioned by Bergounioux (1952:2304) and Hummel (1929:769). Hummel (_op. cit._:771) thought that the Carettochelyidae and "die Chelydroiden" had a common ancestor, and that (_op. cit._:772) the origin of the Trionychidae was older than those two groups. Dunn (1931:109) wrote that the Kinosternidae, Carettochelyidae and Dermatemydidae represented the same general ancestry. Williams (1950:552) has shown the resemblance of the cervical articulations in members of the Chelydridae (including Staurotypinae and Kinosterninae) and the Central American family Dermatemydidae. The consensus of opinion, then, is that the families Trionychidae, Carettochelyidae, Chelydridae and Dermatemydidae are relatively closely related.

Genus =Trionyx= Geoffroy, 1809

_Testudo_ Linnaeus (in part), Syst. Nat., Ed. 10, 1:197, 1758; type, _Testudo graeca_ Linnaeus by subsequent designation (Fitzinger, 1843:29).

_Trionyx_ Geoffroy, Ann. Mus. Hist. Nat. Paris, 14:1, August, 1809; type, _Trionyx aegyptiacus_ (= _Testudo triunguis_ Forskål) by original designation.

_Apalone_ Rafinesque, Atlan. Jour., Friend of Knowledge, Philadelphia, 1 (No. 2, Art. 12):64, Summer, 1832; type, _Apalone hudsonica_ (= _Trionyx spiniferus_ Lesueur) by monotypy.

_Mesodeca_ Rafinesque, Atlan. Jour., Friend of Knowledge, Philadelphia, 1 (No. 2, Art. 12):64, Summer, 1832; type _Mesodeca bartrami_ (= _Testudo ferox_ Schneider) by monotypy.

_Aspidonectes_ Wagler, Naturl. Syst. Amphib., p. 134, 1830; type, _Aspidonectes aegyptiacus_ Wagler (= _Testudo triunguis_ Forskål) by subsequent designation (Fitzinger, 1843:30).

_Amyda_ Fitzinger, Ann. Wiener Mus. Naturg., 1:110, 120, 127, 1835; type, _Amyda subplana_ Fitzinger by subsequent designation (Fitzinger 1843:30).

_Gymnopus_ Duméril and Bibron, Erpét. Gén., 2:472, 1835; new (substitute) name for _Aspidonectes_ Wagler.

_Pelodiscus_ Fitzinger, Ann. Wiener Mus. Naturg., 1:110, 120, 127, 1835; type, _Pelodiscus sinensis_ Fitzinger by subsequent designation (Fitzinger, 1843:30).

_Platypeltis_ Fitzinger, Ann. Wiener Mus. Naturg., 1:109, 120, 127, 1835; type, _Platypeltis ferox_ by subsequent designation (Fitzinger, 1843:30).

_Potamochelys_ Fitzinger, Syst. Rept., p. 30, 1843; type, _Aspidonectes javanicus_ Wagler (= _Testudo cartilaginea_ Boddaert) by original designation.

_Tyrse_ Gray, Cat. Tort. Croc. Amphis. Brit. Mus., p. 48, 1844; type, _Tyrse nilotica_ Gray (= _Testudo triunguis_ Forskål) by tautonomy (_Tyrse_, a name for the Nile River).

_Callinia_ Gray, Proc. Zool. Soc. London, p. 222, 1869; new (substitute) name for _Aspidonectes_ of Agassiz (1857:403); type, _Callinia spicifera_ (mispelling for _spinifera_) Gray by subsequent designation (Stejneger, 1907:514).

_Euamyda_ Stejneger, Bull. Mus. Comp. Zool., 94:7, 9, 12, 1944; new (substitute) name for _Amyda mutica_ of Agassiz (1857:399); type, _Amyda mutica_ Agassiz by monotypy.

_Type Species._--_Trionyx aegyptiacus_ (= _Testudo triunguis_ Forskål).

_Diagnosis._--Cutaneous femoral valves absent; width of postorbital arch of skull less than diameter of orbit; pterygoids usually not contacting opisthotics; carapace lacking prenuchal bone and marginal ossifications; nuchal bone lacking conspicuous ventral ridges; posterior margin of nuchal overlying first pair of pleurals; lateral parts of nuchal bone overlying second pair of ribs; neurals seven or eight, rarely six or nine; pleurals seven or eight pairs, posterior one or two pairs sometimes in contact medially; distinct suture usually present between hyoplastra and hypoplastra; most laterad prong of posteromedial process of hypoplastra inserted between bifid anterolateral process of xiphiplastra.

_Synonomy._--Geoffroy published a synopsis of the species he recognized (1809) prior to his formal description of the genus _Trionyx_ (1809a). Schweigger, nevertheless, probably was the first person to recognize the soft-shelled turtles as a distinct group, and he proposed for it the name _Amyda_ in an unpublished manuscript that he sent to Geoffroy. The latter author (1809a:15) relegated the name _Amyda_ to the synonomy of _Trionyx javanicus_ by means of the following entry: "_Amyda javanica._ Schweigger, dans un manuscript communique a l'Institut." Stejneger (1944:7) maintained that this publication of Schweigger's monotypic generic name clearly established its availability for the species congeneric with _Amyda javanica_ (= _Testudo cartilaginea_ Boddaert, 1770). Loveridge and Williams (1957:422) contend that this mere mention of the name _Amyda_ neither constitutes the proposal of a new name nor validates it, and that the first valid usage of the name _Amyda_ is that of Fitzinger (1835:120), who later (1843:30) designated the type species as _Amyda subplana_. The name _Amyda_ cannot date from _Oken_ (1816:348) as Volume 3 [Zoologie] of his Lehrbuch der Naturgeschichte published in 1815-1816 has been placed on the Official Index of Rejected and Invalid Works in Zoological Nomenclature with the Title No. 33; see Opinion 417 (Hemming, 1956).

There has been considerable debate as to whether Geoffroy did or did not designate a type species of the genus _Trionyx_ (1809a). Although not specifically designated as the type species, _Trionyx aegyptiacus_ (= _Testudo triunguis_ Forskål) is considered by Smith (1930:2), Schmidt (1953:108, footnote), and Loveridge and Williams (1957:422) to have been sufficiently indicated by Geoffroy as the type species. But Stejneger (1944:6), H. M. Smith (1947:122), Conant and Goin (1948:11), and Mertens and Wermuth (1955) maintained that Geoffroy did not adequately designate a type species, and that Fitzinger (1843:30) designated the type species as _Trionyx granosus_ (= _Lissemys punctata_), a synonym of Geoffroy's species, _coromandelicus_.

If Fitzinger's designation of a type species is accepted, the name _Trionyx_ is applicable to the forms herein referred to _Lissemys_, and _Amyda_ to the American forms. If Geoffroy's designation is accepted, the American forms are referable to _Trionyx_, and _Amyda_ is a synonym.

The preceding includes only those generic names (listed in chronological order) that have been applied to Recent American soft-shelled turtles. Generic synonyms of the genus _Trionyx_ applicable to Old World species are listed by Stejneger (1907:514), Smith (1931:165), and Loveridge and Williams (1957:420-21).

_Trionyx_ is the most widespread genus of the family; most of the species occur in southeastern Asia. All North American soft-shelled turtles belong to this genus.

For quick reference, all the specific and subspecific names proposed for soft-shelled turtles in North America are listed below in alphabetical order (left hand column) with their nomenclatural status as recognized in this paper. The synonyms are listed in the account of the appropriate species or subspecies, and are discussed under the subsection entitled "Remarks."

_agassizi_ _Trionyx spinifer asper_ _annulifer_ _Trionyx spinifer spinifer_ _argus_ _Trionyx spinifer spinifer_ _asper_ _Trionyx spinifer asper_ _ater_ _Trionyx ater_ _bartrami_ _Trionyx ferox_ _emoryi_ _Trionyx spinifer emoryi_ _calvatus_ _Trionyx muticus calvatus_ _ferox_ _Trionyx ferox_ _georgianus_ _Trionyx ferox_ _georgicus_ _Trionyx ferox_ _harlani_ _Trionyx ferox_ _hartwegi_ _Trionyx spinifer hartwegi_ _hudsonica_ _Trionyx spinifer spinifer_ _mollis_ _Trionyx ferox_ _microcephalus_ _Trionyx muticus muticus_ _muticus_ _Trionyx muticus muticus_ _nuchalis_ _Trionyx spinifer spinifer_ _ocellatus_ _Trionyx spinifer spinifer_ _olivaceus_ _Trionyx spinifer spinifer_ _spiniferus_ _Trionyx spinifer spinifer_

Variation

Aside from qualitative variations and comparisons of patterns of pigmentation the following external measurements (to the nearest millimeter) were used.

_Length of plastron_: Maximal straight-line measurement (midventrally), from the anteriormost region of the ventral surface to the posterior end of the plastron; this measurement includes an anterior cartilaginous part.

_Length of carapace_: Maximal, straight-line measurement (middorsally), from the nuchal region to the posteriormost region of the free edge of the carapace.

_Width of carapace_: Maximal, straight-line measurement between the lateral margins of the carapace.

_Plane of greatest width of carapace_: Maximal, straight-line measurement from the posteriormost region of the free edge of the carapace to a point on the middorsal line at the level or plane of the greatest width of the carapace; this measurement and the last two, of course, include the fringing cartilaginous parts of the dorsal bony carapace.

_Width of head_: Maximal measurement between the lateral margins of the head.

_Length of snout_: Measurement from tip of snout to interorbital region of least breadth.

_Diameter of ocellus_: Maximal outside diameter of largest (not conspicuously ovoid or oblong) ocellus on carapace.

The following ratios were developed from the measurements. Reference to these ratios will be made by the abbreviations within the parentheses: length of carapace/length of plastron (CL/PL); length of carapace/width of carapace (CL/CW); length of carapace/plane of width of carapace (CL/PCW); length of plastron/width of head (PL/HW); width of head/length of snout (HW/SL); diameter of ocellus/length of plastron (OD/PL).

Secondary Sexual Variation

_Size_

In many species of turtles, females are larger than males; the difference in size between the sexes is probably most pronounced in aquatic emydids. The ten largest individuals of each sex were selected to indicate the relative difference in size between the sexes of the three American species of _Trionyx_ (excluding _ater_, Table 2). Female soft-shelled turtles attain a larger size than males. _T. ferox_ is the largest species; _muticus_ is the smallest. The approximate maximal size of each sex and the difference in size between the sexes are more correctly expressed for _spinifer_ and _muticus_ than for _ferox_, because fewer specimens of _ferox_ were examined; presumably the approximate maximal size of males and females of _ferox_ is larger than is indicated in Table 2.

TABLE 2. Secondary Sexual Difference in Maximal Size of North American Species of the Genus Trionyx (excluding ater) Based on the Ten Largest Specimens of Each Sex of Each Species. The Extremes Precede the Mean (in parentheses).

=============+============================ SPECIES | Plastral length (cm.) -------------+---------+------------------ _ferox_ | males | 17.0-26.0 (20.0) | females | 23.3-34.0 (27.9) | | _spinifer_ | males | 13.8-16.0 (14.4) | females | 26.0-31.0 (28.0) | | _muticus_ | males | 11.8-14.0 (12.3) | females | 17.7-21.5 (18.9) -------------+---------+------------------

_Pattern_

Secondary sexual differences in pattern are probably more pronounced in soft-shelled turtles than in other species of turtles, except perhaps for the well-known melanism and concomitant obliteration of pattern acquired by some adult males of the _scripta_ section of the genus _Pseudemys_.

The difference in pattern between the sexes of American species varies with size of the individual and with the species and subspecies. The juvenal pattern of some individuals of _T. spinifer asper_ differs according to sex. In the other species and subspecies, there are no secondary sexual differences in the juvenal pattern. That pattern in females of all species and subspecies is partly or entirely obscured by a mottled and blotched pattern as growth proceeds. This mottled and blotched pattern is present on females not yet sexually mature, and is of contrasting lichenlike figures, and in other individuals is less contrasting and a more uniform coloration. The largest males of _T. spinifer_ retain a conspicuous juvenal pattern; in those of _muticus_ the pattern may be well-defined or partly modified and obscured, whereas in large males of _ferox_ the juvenal pattern is ill-defined or absent. No male normally acquires a contrasting mottled and blotched pattern on the carapace. The pattern on the carapace of many large individuals of _ferox_ is not distinctive as to sex.

On the dorsal surface of the soft parts of the body there is a contrasting pattern in adult males and hatchlings of some forms, but in most large females the pattern is usually reduced to a near-uniform coloration; the pattern on adult males of _ferox_ and _muticus_ is not contrasting and resembles that on large females.

_Coloration_

Because most specimens examined were preserved, the detection of secondary sexual differences in coloration was difficult. There is one difference in coloration between the sexes in the subspecies _T. s. emoryi_. Males from the Río Grande drainage, at least those from the Big Bend region of Texas, and southwestward in the Río Conchos into Chihuahua, México, are bright orange on the side of head (postlabial and postocular pale areas); an orange tinge also occurs in pale stripes on the snout, and pale orange blotches sometimes occur on the dorsal surfaces of limbs, especially the hind limbs. The coloration of these areas on females is pale yellow, lacking orange.

_Tuberculation_

In all subspecies of _spinifer_ the carapace of adult males is "sandpapery" owing to abundant, small, spiny tubercles distributed over its surface; all females lack spiny tubercles on the surface of the carapace.

_Length of Tail_

Elongation of the preanal region of the tail resulting in the extension of the cloacal opening beyond the posterior edge of the carapace occurs in males of several kinds of turtles, including _Trionyx_, at least in those from Louisiana, Texas, and Lake Texoma, Oklahoma (Webb, 1956:121). Probably this elongation is characteristic of males of all American softshells. Some females of _spinifer_ and _muticus_ that exceed the maximum size attained by males have the tip of the tail and cloacal opening extending a short distance beyond the posterior edge of the carapace. Some large females of _ferox_ have more elongate tails than those of _spinifer_ and _muticus_.

_Width of Alveolar Surfaces of Jaws_

Stejneger (1944:34-36, pl. 6) commented on a series of large skulls of _ferox_ mostly from Kissimmee, Florida, some of which had conspicuously expanded alveolar surfaces. He suggested that the condition was confined to large males. A scattergram (Fig. 2) based on measurements obtained from 45 skulls of _ferox_ shows widened alveolar surfaces of the upper jaws on some of the larger skulls. Because the maximal size of adult males is unknown and the difference in size between the sexes of _ferox_ is slight, such large skulls might represent either sex. The sex had been recorded for only three of the 45 skulls; none of the three exceeded 82 millimeters in basicranial length or had widened alveolar surfaces. Some of the larger skulls of approximately the same size differ markedly in width of the alveolar surfaces; this difference suggests that both sexes are included and that the sexes may be of approximately the same maximal size. On the other hand, the variation observed in skulls is possibly confined to one sex. To judge from what is known of the maximal sizes of the sexes of _spinifer_ and _muticus_ (see Table 2), skulls of _ferox_ of more than 85 millimeters in basicranial length probably are of females. The largest alcoholic male (dissected) of _ferox_ that I examined had a width of head of approximately 46.5 millimeters; that measurement corresponds to a basicranial length of 70 to 75 millimeters. The specimen of which measurements are depicted by the uppermost symbol in the scattergram (represented by KU 16528) was recorded as a female. Large females of _T. s. asper_ from rivers emptying into the Atlantic Ocean have broadened alveolar surfaces.

_Length of Claw_

Secondary sexual differences in length of claw on the forelimb are pronounced in some kinds of turtles. Cahn (1937:178) stated that the female of _Trionyx muticus_ usually has long claws on the hind feet, while the male has long claws on the forefeet, but I am unable to substantiate his statement. Measurements of length of the third claw on the hind limb taken in 41 males and 45 females of _spinifer_ from Louisiana showed no secondary sexual difference.

Ontogenetic Variation

_Pattern_

In all species and subspecies the juvenal pattern is replaced in females as growth proceeds by a mottled and blotched pattern that is contrasting or of nearly uniform coloration. The blotched pattern (of lichenlike figures) is evident on the carapaces of most females that have plastra so long as 8.0 centimeters. The contrasting juvenal pattern on the dorsal surfaces of the soft parts of the body is correspondingly modified in females, but at a size larger than 8.0 centimeters. Size of ocelli (OD/PL) in _T. s. spinifer_ and _hartwegi_ seems to vary ontogenetically (see section on Geographic Variation).

Some hatchlings have blotched patterns (_T. spinifer asper_, TU 16689.2, plastral length, 3.5 cm.); the largest females examined that did not show any evidence of mottling were two _asper_ having plastrons 7.6 and 8.0 centimeters in length. Variation in color and pattern probably is modified greatly by the environment (Heude _in_ Stejneger, 1907:518, footnote d) and the physiological condition of the individual. Smith, Nixon and Minton (1949:92) reported that a female of _T. s. hartwegi_ developed a striking melanistic pattern in captivity and they concluded that patterns of soft-shelled turtles may be produced not only by conventional chromatophores, but also by other depositions, both intra- and extracellular. TU 16170, taken from brackish water at Delacroix Island, St. Bernard Parish, Louisiana, is the only adult male I have seen that had a blotched pattern (orange-brown in life) on the carapace in addition to the juvenal pattern. One female of _muticus_, KU 48229, having a plastral length 14.5 centimeters, retained a well-defined juvenal pattern, and lacked a mottled and blotched pattern (see Pl. 46).

_Tuberculation_

Males of the subspecies of _spinifer_ develop small, sharp tubercles on the dorsal surface of the carapace when sexually mature. As growth proceeds, the minute prominences along the anterior edge of the carapace on hatchlings of both sexes of _spinifer_ change in shape to conical projections or low, flattened, scarcely-elevated prominences, depending on the subspecies (Fig. 8).

Large females of _spinifer_ and _ferox_ acquire enlarged, flattened knobs in the nuchal region and posteriorly in the center of the carapace.

_Length of Tail_

The preanal region of the tail rapidly elongates in males of all soft-shells when they are sexually mature.

_Width of Alveolar Surfaces of Jaws_

The alveolar surfaces of the jaws are conspicuously broadened in large adults of _ferox_, and females of that population of _T. s. asper_ in the Atlantic Coast drainage.

_Ratios_

Width of head increases at a rate slightly slower than does the length of the plastron (PL/HW, Fig. 3). The change in proportions is most pronounced at a plastral length of 7.5 to 8.0 centimeters. In general, the head is narrowest in _muticus_ and widest in _ferox_. _T. s. asper_ and _emoryi_ seemingly have the widest heads among the subspecies of _spinifer_. Geographically width of head increases from _spinifer_ and _hartwegi_ through _pallidus_ and _guadalupensis_ to _emoryi_. _T. ater_ terminates the cline; 12 specimens, ranging in plastral length from 9.6 to 18.4 centimeters, resemble _ferox_ and _asper_ in having wide heads (average PL/HW of 4.93).

The carapace increases in width more slowly than it increases in length (CL/CW, Fig. 4). The change in proportions is most pronounced when the carapace is 8.0 to 8.5 centimeters in length. Ontogenetically _muticus_ varies least and _ferox_ most; large specimens of _ferox_ have narrower carapaces than _muticus_ of corresponding size. There is also an indication of a geographical gradient that parallels the cline mentioned above for PL/HW. There is a gradual decrease in width of carapace from _pallidus_ through _guadalupensis_ to _emoryi_. Of the subspecies of _spinifer_, _emoryi_ has the narrowest carapace and resembles _ferox_. In _T. ater_ this cline is accentuated and terminates; 12 specimens, ranging in plastral length from 9.6 to 18.4 centimeters, resemble _ferox_ and _emoryi_ in having narrow carapaces (average CL/CW of 1.32).

_Osteological Characters_

Closure of the anterior, paravertebral fontanelles on the bony carapace, and size and number of plastral callosities are subject to ontogenetic variation (see sections entitled "Carapace" and "Plastron").

Geographic Variation

Geographic variation occurs in _Trionyx spinifer_ and _T. muticus_. The variant populations of _spinifer_ are segregated into six subspecies, those of _muticus_ into two. In the subspecies of _spinifer_ there is both group variation and clinal variation.

Group Variation

The six subspecies of _spinifer_ can be separated into two groups on the basis of the juvenal pattern. One group (subspecies _spinifer_, _hartwegi_ and _asper_) has a pattern of dark spots or ocelli of various sizes on the carapace, whereas the other group (subspecies _pallidus_, _guadalupensis_ and _emoryi_) has a pattern of small white dots or tubercles on the carapace. The two groups differ also in the manner in which the mottled and blotched pattern first appears on the carapace of females. Usually, contrasting lichenlike figures initially surround the dark spots or ocelli on the carapace in females of the _spinifer_ group (less evident in _pallidus_), whereas females of the _emoryi_ group usually lack a contrasting pattern early in ontogeny. In general, the two groups differ in the degree of pigmentation. The _spinifer_ group has larger marks and more contrasting patterns on the head and limbs, and more extensive pigmentation on the ventral surface than members of the _emoryi_ group. _T. ater_ is more closely related to those subspecies of the _emoryi_ group but differs in having the ventral surface heavily speckled with black and an over-all blackish, dorsal coloration; the underlying pattern of _ater_ resembles that of _emoryi_.

Clinal Variation

Several characters are arranged in a geographical gradient or cline. Some characters are relatively uniform and represent a terminus in the _spinifer_ group. Some characters change gradually and successively through the subspecies _pallidus_ and _guadalupensis_, and terminate in _emoryi_ and _T. ater_. Some characters of _ater_, in turn, show affinity with _T. muticus_ and _T. ferox_.

_Pattern on Snout_

The pattern (Fig. 5) on the snout usually consists of pale, dark-bordered stripes that form an acute angle in front of the eyes in _spinifer_, _hartwegi_ and _asper_, but the corresponding marks form a dark triangle the base line of which joins the anterior margins of the orbits in _emoryi_ and usually in _guadalupensis_. In _pallidus_, the geographic range of which is between _guadalupensis_ and _hartwegi_, there are different patterns that are in various degrees intermediate between those described immediately above for _hartwegi_ and _guadalupensis_.

_Pattern on Side of Head_

The change in pattern (Fig. 6) and its contrast with the ground color on the side of the head parallels the sequence of changes in pattern on the snout. The pattern on the side of head contrasts with the ground color and consists of dark markings below the eye and on the neck, an indication of a postlabial stripe, and a pale, dark-bordered postocular stripe that may be variously interrupted (_spinifer_ and _hartwegi_; _asper_ usually has uninterrupted postocular and postlabial stripes that unite on the side of the head). The pattern is contrasting but variable in _pallidus_. _T. s. emoryi_ and usually _guadalupensis_ have fewer dark markings, sometimes none, and an interrupted postocular pale stripe that produces a pale blotch just behind the eye.

_Pattern on Dorsal Surface of Limbs_

A corresponding sequence of change occurs in the size of dark markings on the dorsal surface of the limbs (Fig. 7). The hind limb usually has larger markings than the forelimb. The change is gradual from larger and darker markings (contrasting pattern) in _hartwegi_, _spinifer_ and _asper_ to smaller and paler markings (non-contrasting pattern) in _emoryi_.

_Tuberculation_

There is also a cline in tuberculation (Fig. 8) that parallels geographically the sequence of changes in patterns mentioned immediately above. The size of the tubercles along the anterior edge of the carapace changes in both sexes from those that are enlarged and equilateral or conical in shape in _spinifer_, _hartwegi_, _asper_ and _pallidus_ to those that are scarcely elevated in _guadalupensis_, _emoryi_ and _T. ater_. Indeed, in the three kinds mentioned last, the tubercles are absent in some specimens. There seems to be a corresponding reduction in the size and number of small, sharp-tipped tubercles that cover the carapace in adult males; the carapace of _T. ater_ is mostly smooth and has only a few small, whitish tubercles.

_Ratios_

The clinal tendencies in PL/HW (Fig. 3) and CL/CW (Fig. 4) that parallel those mentioned above for pattern and tuberculation have already been mentioned under the section "Ontogenetic Variation."

The ratio of CL/PCW (Fig. 9) was used in an effort to show further differences in the shape of the carapace, especially the plane on the carapace where the greatest width occurs. Figure 9 shows the greatest width to be approximately midway between the anterior and posterior ends in the subspecies _spinifer_, _hartwegi_ and _asper_, and in the species _ferox_ and _muticus_ (CL/PCW of 2.00). The greatest width of carapace is more posterior and at approximately the same plane in _pallidus_ and _guadalupensis_, and farther posterior in _emoryi_. Calculated ratios for 12 specimens of _T. ater_ average 2.15, a value that suggests closer affinity with _pallidus_, _guadalupensis_ and _emoryi_ than to the other species and subspecies.

Comparison of the relative lengths of snout (HW/SL, Fig. 10) in different populations of _T. spinifer_ shows a character gradient. To facilitate a comparison utilizing large samples, the subspecies _spinifer_ was combined with _hartwegi_, and _pallidus_ with _guadalupensis_. The snout is longer in the subspecies _spinifer_ and _hartwegi_ than in _emoryi_; the length of the snout of _emoryi_ resembles that of _T. ferox_. The snout is proportionately the longest in _T. muticus_. The average ratio of HW/SL for 12 individuals of _T. ater_ is 1.37, and is nearer that of _pallidus_, _guadalupensis_, _emoryi_ and _ferox_ than that of _muticus_ or the other subspecies of _T. spinifer_.

Size of the ocelli increases from west to east in populations of _T. spinifer_ in the upper Mississippi River and Great Lakes drainages.

The ratio of OD/PL (Fig. 11) varies considerably but gradually increases from Kansas northeastward to Michigan. The minimal diameter of any ocellus recorded was one millimeter; solid dots on the carapace (_hartwegi_) were also recorded as one millimeter. Larger ratios are usually derived from measurements of larger individuals. Seemingly, there should be a clinal tendency in ontogenetic variation paralleling the size of ocelli and dependent on it; ontogenetic variation should be least in western populations in which the size of ocelli does not change appreciably with increasing size, and should be greatest in eastern populations in which the ocelli on adult males are larger than those on the carapace of young turtles. It is difficult to demonstrate ontogenetic variation because specimens of corresponding size from the same general area may have ocelli of different sizes. The gradient in size of ocelli is also indicated by specimens from other states. I have the subjective impression that there is least variation in specimens from Michigan (Great Lakes-St. Lawrence River drainage), but this is not clearly shown by Figure 11.

Character Analysis

_Snout_

The snout (Fig. 12) is tubate having terminal nostrils separated by a vertical septum. One of the principal characters distinguishing _T. ferox_ and _T. spinifer_ from _T. muticus_ is a lateral, whitish ridge projecting from each side of the nasal septum (hereafter referred to as septal ridges but often referred to in the literature as a papilla). The shape of the end of the snout is truncate in _T. ferox_ and _T. spinifer_, and the nostrils are larger than in _T. muticus_. In _muticus_ the snout usually terminates somewhat obliquely, and the nostrils tend to be slightly inferior; also, the end of the snout is usually rounded and somewhat pointed, causing the nostrils to be visible in lateral view. Some _T. muticus_ do not differ markedly from _ferox_ or _spinifer_ in shape of the end of the snout. Stejneger (1944:14) mentioned indication of a septal ridge that did not reach the opening of the nostril in _muticus_. I have slit the outer edge of the nostril on several specimens of _muticus_, and have not noticed an indication of a septal ridge.

_Tuberculation_

Tubercles or obtuse prominences occur on the anterior edge of the carapace (Fig. 8) or on the dorsal surface of the carapace. _Trionyx muticus_ lacks tubercles, although some individuals show shallow, widely spaced wrinkles that suggest prominences on the anterior edge of the carapace. Both sexes of _T. ferox_ have prominences, resembling flattened hemispheres, on the anterior edge of the carapace and in the nuchal region. Large females of _ferox_ have obtuse prominences in the center of the carapace posteriorly, some of which are often arranged in longitudinal rows. The surface of the carapace in both sexes of _T. ferox_ has small closely-set, blunt tubercles arranged in rows that resemble longitudinal ridges (most evident in juveniles).

Large females of _T. spinifer_ have obtuse prominences in the center of the carapace posteriorly, some of which in many specimens are arranged in longitudinal rows; I cannot discern any correlation of number or arrangement of prominences with size in _spinifer_ or _ferox_. The carapace in adult males of _spinifer_ bears small, sharp tubercles that make the surface feel like sandpaper. The tubercles on the anterior edge of the carapace in adults of both sexes vary from round to equilateral and conical to low and flattened (see comments on tuberculation under subsection entitled "Geographic Variation"). Some large females of the same subspecies have tubercles on the anterior edge of the carapace that may be conical (higher than wide) or equilateral. The difference in shape of the tubercles seems not to be correlated with size because one _T. s. pallidus_, 30.5 centimeters (TU 13212) has prominent but blunted and equilateral tubercles, whereas, another female of _pallidus_, 20.8 centimeters (TU 13210), from the same locality has higher, conical tubercles. The blunted, equilateral tubercles may be the result of environmental wear, or the difference in shape of tubercles may be due to individual variation.

_Pattern on Carapace_

Two features of the pattern on the carapace are of taxonomic worth: 1) the width and distinctness of the pale rim at the periphery of the carapace (marginal rim), if present, and 2) the kind of pattern on the carapace (juvenal pattern). The marginal rim is absent in females of _T. ater_, and only faintly evident in males. The marginal rim is obscured or absent (adult males and females) and is not separated from the ground color of the carapace by a dark marginal line in hatchlings of _T. ferox_. The carapace of _T. muticus_ has a marginal rim that is usually separated from the ground color of the carapace by an ill-defined, dark marginal line; some individuals lack the marginal dark line. The subspecies of _T. spinifer_ have a well-defined, dark, marginal line that separates the marginal rim from the ground color of the carapace; _T. s. asper_ has more than one dark marginal line on the carapace. The marginal rim is ill-defined and blotched, or absent, in large females of all species of _Trionyx_.

The marginal rim is widest at the posterior end of the carapace and lacking in the nuchal area. The width of the pale marginal rim is very narrow, almost to the degree of being absent, in juveniles of _T. ferox_. _T. s. emoryi_ has a pale, marginal rim that is four or five times wider posteriorly than it is laterally, whereas posteriorly the width of the rim in the other subspecies of _T. spinifer_ and in the species _T. muticus_ is only two or three times wider posteriorly than it is laterally.

The juvenal pattern commonly consists of whitish tubercles or dots (_T. s. emoryi_, _T. s. guadalupensis_, _T. s. pallidus_, _T. ater_), large black ocelli (_T. s. spinifer_), small black dots and ocelli (_T. s. hartwegi_, _T. s. asper_), large dusky spots or ocelli (_T. m. calvatus_), or small dusky dots or short streaks and dashes (_T. m. muticus_). Some hatchlings of _pallidus_ and _emoryi_ have a uniform pale brown or tan carapace; hatchlings of _T. ferox_ have a distinctive pattern (Pl. 31). Further comments and illustrations pertaining to kind of pattern on the carapace are offered under the accounts of species and subspecies.

_Pattern on Dorsal Surface of Snout (Fig. 5)_

_T. ferox_ has pale stripes on a dark background that unite in front of the eyes; the dark ground color becomes paler with increasing size, but the stripes retain thick black borders. _T. m. muticus_ has ill-defined, pale stripes that are evident just in front of the eyes and do not extend anteriorly to unite in front of the eyes, whereas _T. m. calvatus_ lacks pale stripes on the snout. The kind of pattern on the dorsal surface of the snout that is characteristic for each of the subspecies of _T. spinifer_ has been mentioned in the discussion of clinal variation.

_Pattern on Side of Head (Fig. 6)_

_T. ferox_ has a pale broad, postocular stripe in contact with the orbit or not, and other pale marks on a dark background; the ground color becomes paler with increasing size, but the stripes and other marks retain thick black borders. _T. m. muticus_ usually has an uninterrupted, dusky-bordered, postocular stripe, whereas _T. m. calvatus_ (in adult males only) has pale postocular stripes with thick blackish borders. The pattern on the side of head that is characteristic for each subspecies of _T. spinifer_ has been mentioned in the discussion of clinal variation.

_Pattern on Dorsal Surface of Limbs (Fig. 7)_

Young specimens of _T. ferox_ have pale marks on a blackish background. As growth proceeds the distinctive contrasting pattern is obliterated and eventually is replaced by a uniform grayish coloration in large adults. The pattern on the limbs of _T. muticus_ is not contrasting, and is almost a uniform grayish, consisting of fine, pale markings. The clinal variation in pattern and kind of pattern on the limbs of the subspecies of _T. spinifer_ has been mentioned in the discussion of clinal variation. Dark markings tend to form streaks that are coincident with the digits, and larger markings occur on the hind limbs than on the forelimbs.

_Marginal Ridge_

The anterolateral edge of the carapace in _T. ferox_ (both sexes and all sizes) is "folded over" into a ridge having a distinct inner margin (Pls. 1 and 2), which is hereafter referred to as the marginal ridge. Siebenrock (1924:184-85) referred to this ridge as a "Hautsäume" and mentioned its occurrence in Old World species of the genus _Trionyx_. The marginal ridge is not present in _T. muticus_, _T. spinifer_ or _T. ater_.

_Ratios_

The means of some samples (Fig. 3) differ in regard to PL/HW, but the ranges of variation overlap so much that little significance can be attributed to the difference. _T. ferox_, and to a lesser extent _T. s. emoryi_ and _T. s. asper_, have slightly larger heads than the other forms. The width of head is proportionately the smallest in _T. muticus_; in most individuals of it having a plastron so long as 13.0 centimeters, the width of the head is less than 16 per cent of the length of the plastron--a percentage that is distinctive.

The visibly narrower carapace (CL/CW, Fig. 4), suggesting an ovoid or oblong shape, in some large individuals of _T. ferox_ and _T. s. emoryi_ is indicated by the large ratio in specimens that have a plastral length of 8.0 centimeters or more. Nevertheless, the degree of overlap of the ranges of variation is such that this ratio is of relatively little use taxonomically.

The greatest width of the carapace is farther posterior in _T. s. emoryi_ than in the other forms (CL/PCW, Fig. 9). The considerable overlap of the range of variation of this ratio for _emoryi_ with the other forms limits its usefulness as a taxonomic character.

The snout is proportionately shortest in _ferox_ and _T. s. emoryi_, and longest in _muticus_ (HW/SL, Fig. 10). The most marked difference in this ratio is between the species _muticus_ and _ferox_; the ranges of variation of those species overlap to a degree that tends to negate the taxonomic usefulness of this character.

Most adults and subadults of _T. ferox_ show clearly in dorsal view the anterolateral portions of the plastron. This condition is much less well developed in some specimens of _T. s. emoryi_. _T. ferox_ is extreme in the ratio CL/PL (relatively the longest plastron or shortest carapace, Fig. 13). _T. s. asper_ has the shortest plastron in relation to length of carapace. Calculated ratios for 12 _T. ater_ average 1.36, a value that suggests close affinity with some subspecies of _T. spinifer_ (_pallidus_, _guadalupensis_, _emoryi_). Because of the degree of overlap of the ranges of variation in all forms, little significance can be attributed to the difference in means of _ferox_ and _asper_.

_Scalation_

Cornified, smooth or cusplike areas occur on each limb, but their number and arrangement are of no taxonomic value. Normally, the anterior surface of each forelimb possesses four cornified areas for which the term antebrachial scales is proposed (Fig. 14). Two of the four scales occur in a more dorsal position; the lateral edge of the proximal one is free and cusplike along a part of its length, whereas the distal scale is smooth-edged. Two scales having their lateral edges free and cusplike are ventral in position, and closer together than the two dorsad scales. Size of the scales and length of the free cusplike edges vary. Occasionally adjacent scales are fused or small additional scales are present. The number, configuration and arrangement of the two cornified areas on each hind limb are constant. One of these scales is smooth-edged and occurs posteriorly on the dorsal surface. The other scale, situated on the ventral surface posteriorly in the region of the heel and distal to the smooth-edged scale of the dorsal surface, has a pronounced, cusplike, free edge.

_Choanal Papillae_

This term refers to the papillate flaps of skin that project from the lateral borders of the internal nares. Webb and Legler (1960:23) noted their presence in softshells, and Parsons (1958) discussed their occurrence in sea turtles of the family Cheloniidae and in the testudinid subfamily Emydinae (1960). In preserved softshells the choanal papillae may extend laterally and partly cover the nares, or may be folded vertically against the lateral borders of the nares; in the latter position the papillae are easily overlooked. To my knowledge, choanal papillae occur in all American species and subspecies of soft-shelled turtles. The free edge of each narial flap shows various degrees of fimbriation. The fimbriated border is least developed (margin nearly entire) in _T. muticus_ and most developed in _T. ater_ and _T. ferox_. In _ater_ at least, the anteriormost portions of the narial flaps seem wider than in the other forms and show a greater degree of fimbriation than the posteriormost parts. The choanal papillae are most easily observed in large specimens.

_Skull_

In general, there is less difference between the skulls of _ferox_ and _spinifer_ than between either of those species and _muticus_ (Stejneger, 1944:10-11). Figure 15 shows the general differences in proportions of the skulls of _spinifer_ and _muticus_; Plate 54 shows the skull of the holotype of _Platypeltis agassizi_ (= _T. s. asper_), which is similar to that of _ferox_; Stejneger (_op. cit._) provided labelled drawings of the skull of _T. spinifer_ as well as photographs of skulls of other forms.

The total of 159 skulls examined by me include 80 of _spinifer_, 50 of _ferox_, and 29 of _muticus_. There are no secondary sexual differences between skulls of corresponding size, except in _agassizi_-form skulls mentioned under the account of _T. s. asper_, and possibly in _ferox_. Most, and possibly all, of the skulls of _muticus_ having a basicranial length of 40.0 millimeters or more, and those of _spinifer_ exceeding 50.0 millimeters must represent females (by correlation of known maximum size of males with greatest width of head, which is, in turn, compared with the greatest width of skull and corresponding basicranial length).

Measurements used include basicranial length (occipital condyle to tip of upper jaw), greatest width (variable in position), greatest width of alveolar surface of maxilla (taken at level immediately posterior to anterior margin of internal choanae), greatest length of internal choanae, and least breadth of maxillary bridge (separating internal choanae and intermaxillary foramen). One ratio developed from the measurements was greatest length of internal choanae/least breadth of maxillary bridge, hereafter referred to as IC/MB. This ratio is discussed under the account of _T. s. asper_.

_Greatest Width_

The position or level on the skull where the greatest width (Table 3) occurs is of some diagnostic value in distinguishing the skulls of _ferox_ from _spinifer_ and _muticus_. Skulls of _ferox_ usually are widest at the level of the quadratojugal (immediately in front of tympanic cavity), whereas skulls of _spinifer_ and _muticus_ usually are widest slightly more posteriorly at a level on the squamosal immediately behind the tympanic cavity. Occasionally the width at the level of the quadratojugal and squamosal is the same, or the greatest width of skull may be ventrad between the quadrates, which are slightly flared laterally. The latter condition possibly is most prevalent in _muticus_.

TABLE 3. Variation in Position of Greatest Width of Skull of North American Species of the Genus Trionyx (excluding ater). The Number of Specimens Examined (in Parentheses) Follow the Specific Names.

================+================================================= | Species POSITION +--------------+-----------------+---------------- | _ferox_ (36) | _spinifer_ (47) | _muticus_ (14) ----------------+--------------+-----------------+---------------- Squamosal | 7 (19%) | 35 (74%) | 11 (79%) Quadratojugal | 26 (72%) | 7 (15%) | 1 (7%) Quadrate | 2 (6%) | | 2 (14%) Squamosal and | | | quadratojugal | | | of same width | 1 (3%) | 5 (11%) | ----------------+--------------+-----------------+----------------

_Supraoccipital Spine_

The ventral surface of the supraoccipital spine in _muticus_ lacks a medial ridge, and gradually increases in width anteriorly, so that it is widest proximally in the region of the roof of the foramen magnum. In _ferox_ and _spinifer_, the ventral surface, usually having a medial ridge, is narrow and of the same width throughout its length or somewhat flared distally. The ventral surface of the supraoccipital spine, which is widest proximally in _muticus_, is always narrow proximally in _ferox_ and _spinifer_. The ventral surface of the supraoccipital spine of one skull of _spinifer_, USNM 91311, differs little from that of _muticus_.

_Foramen Magnum_

The shape of the foramen magnum is generally rhomboidal in _spinifer_ and _ferox_; the ventral angle is semicircular, the lateral angles obtuse, and the dorsal angle more acute. The shape of the foramen magnum in _muticus_ is ovoid, higher than wide; the sides are evenly rounded.

_Opisthotic-Exoccipital Spur_

Skulls of _spinifer_ normally have the fenestra postotica partly restricted by a medially-slanting, descending spur from the roof of the fenestra postotica; the spur incorporates the suture between the exoccipital and opisthotic and includes parts of those two bones. On one skull (KU 2824) the spur is displaced more medially and does not incorporate the opisthotic. The descending spur contacts the pterygoid ventrally forming a complete bony strut traversing the fenestra postotica in some skulls (KU 2228, 2666, 2762, TU 15423, MCZ 46621, TU 15415, right side only). The fenestra postotica on skulls of _ferox_ and especially _muticus_ is not normally restricted by an opisthotic-exoccipital spur.

Often the spur is reduced and indicated by a smooth projecting ridge. Sometimes the spur or ridge is absent on skulls of _spinifer_, and I have seen no well-developed spur on a skull of _muticus_. The development of the spur is not due to ontogenetic variation. There is some variation in development of the spur on either side of the skull; two skulls of _ferox_ have the combination ridge/absent, and two of _spinifer_ have the combinations ridge/spur and spur/absent. The frequency (based on counts of individual skulls) and the degree of development of the spur among the three species is indicated in Table 4.

TABLE 4. Frequency and Degree of Development of Opisthotic Exoccipital Spur of North American Species of the Genus Trionyx (excluding ater). The Number of Specimens Examined (in Parentheses) Follow the Specific Names.

======================+================================================= | Species DEVELOPMENT OF SPUR +--------------+-----------------+---------------- | _ferox_ (43) | _spinifer_ (68) | _muticus_ (29) ----------------------+--------------+-----------------+---------------- spur (well-developed) | 1 (2%) | 45 (66%) | ridge (reduced) | 7 (16%) | 20 (30%) | 1 (3%) absent | 35 (82%) | 3 (4%) | 28 (97%) ----------------------+--------------+-----------------+----------------

Loveridge and Williams (1957:415, footnote) cited Siebenrock who mentioned a descending process of the opisthotic in _Dogania_ (= _Trionyx_) _subplana_ and _Trionyx sinensis_. I have not seen an ascending process of the pterygoids on skulls of American softshells as described by Loveridge and Williams (_op. cit._:414, 429, fig. 54) for _Lissemys_, _Cyclanorbis_, _Cycloderma_ and some _Trionyx triunguis_.

_Opisthotic Wing_

This term refers to the laterally directed, posterior part of the opisthotic that is visible in occipital, lateral and ventral views. In ventral view the opisthotic wing is most easily seen and is wider in _muticus_ than in _spinifer_ or _ferox_. In _muticus_ the distal part is truncate, whereas in _ferox_ and _spinifer_, it is more tapered and gently rounded, although somewhat unevenly flared medially. Also there is more of a downward curvature (in ventral view) of the opisthotic wing in _muticus_ than in _ferox_ or _spinifer_; consequently the tip of the wing in _muticus_ is often just visible in dorsal view (on lateral side of squamosal), certainly in lateral view. The distal part or tip of the opisthotic wing is not visible in dorsal view on skulls of _ferox_ or _spinifer_.

_Articular Surface of Quadrate_

The ventral surface of the quadrate that articulates with the mandible is composed of a lateral condyle and a medial articular surface. The condyle and medial articular surface are separated by a furrow. On skulls of _ferox_ and _spinifer_ the lateral condyle, which is not conspicuously tapered posteriorly, is slightly larger than the medial articular surface, and the furrow is shallow. On skulls of _muticus_, the lateral condyle is conspicuously tapered posteriorly, is slightly smaller than the medial articular surface, and the furrow is deep.

_Contact of Maxillaries Above Premaxillaries_

The contact of the maxillaries above the premaxillaries is of diagnostic value in distinguishing skulls of _ferox_ and _spinifer_ from those of _muticus_. I have seen no skulls of _muticus_ on which the maxillaries were in contact, and no skulls of _ferox_ on which the maxillaries were separated. Stejneger (1944:19), however, reported a skull of _muticus_ (USNM 102677) having the maxillaries in contact. Maxillaries are in contact (sometimes just barely) in 65 of 74 skulls of _spinifer_ (88%); the premaxillaries are separated on nine skulls (12%).

_Carapace_

The dorsal surface of the bony carapace of American trionychids consists of a nuchal, seven or eight pairs of pleurals, and seven or eight, rarely nine, neurals (Fig. 16). The lateral parts of the nuchal overlie the second pair of ribs. The distal parts of the second through the ninth pair of ribs extend laterally beyond the lateral edges of the pleurals. There are no marginal ossifications. The posterior part of the bony carapace bears blunt, rounded or ovoid to linear, prominences mostly on the last pair of pleurals principally on large females of _spinifer_ and _ferox_; I have seen only one adult male (stuffed, MCZ 46633) having a semblance of welts on the bony carapace. The nuchal, pleurals and neurals are sculptured.

As growth proceeds, the single, transversely-oriented, fontanelle of young turtles that separates the nuchal from the first neural and first pair of pleurals divides into two fontanelles that generally decrease in size and finally disappear. Occasionally only one (unilateral) large fontanelle is present (USNM 54734, _muticus_). The largest specimens noted that retain fontanelles are a _ferox_ (USNM 029474) having a plastron 24 centimeters long, and a _spinifer_ (USNM 54731) having a plastron 20 centimeters long. The fontanelles probably are present in some larger individuals.

Most variation concerns the number of neurals and pairs of pleurals, and their arrangement posteriorly (H. M. Smith, 1947:121, table; Stejneger, 1944:18). Table 5 shows the frequency of occurrence of the number of neurals, pairs of pleurals, and the separation or contact of the seventh pair of pleurals; figure 16 illustrates some of the configurations of these plates posteriorly (e, g, and i not included in Table 5). The eighth pair of pleurals is reduced or absent (Loveridge and Williams, 1957:417). Eight neurals and eight pairs of pleurals occur in all three species. The seventh pleurals may contact each other in all three species, and their separation has been observed only in the species _spinifer_ and _muticus_. Seven neurals and contact of the seventh pair of pleurals, or eight neurals and separation of the seventh pair of pleurals from each other occurs with approximately equal frequency in the species _muticus_. _T. ferox_ and _spinifer_ most often have seven neurals, seven pairs of pleurals, and the seventh pair of pleurals in contact. Stejneger (_loc. cit._) mentioned a specimen in MCZ having nine neurals; I recorded nine neurals for USNM 54734 (Fig. 16i) for which Stejneger (_loc. cit._) recorded eight. AMNH 57384 (_ferox_) has a small eighth pleural on the left side only, and USNM 115939 (_muticus_) has an eighth pleural only on the right side (Fig. 16h). Anomalous conditions observed included: an accessory bone between the first and second pleurals on the right side that contacts the first and second neurals in USNM 54733, (_muticus_); only six neurals in USNM 95193 (_spinifer_); a small accessory bony element between the first and second neurals in AMNH 57383 (_ferox_); and, only six pleurals (second and third fused) on the right side in USNM 54734 (_muticus_).

TABLE 5. Frequency of Occurrence of Number of Neurals, Pairs of Pleurals, and Separation or Contact of the Seventh Pair of Pleurals Among Species of American Soft-shell Turtles

===================+=================+================================== Number | Contact (+) or | Species --------+----------+ separation (-) +---------+------------+----------- | Pairs of | of seventh pair | _ferox_ | _spinifer_ | _muticus_ Neurals | pleurals | of pleurals | (16) | (60) | (34) --------+----------+-----------------+---------+------------+----------- 7 | 7 | + | 9 (56%) | 50 (83%) | 13 (38%) 7 | 8 | + | 5 (31%) | 2 (3%) | 2 (6%) 8 | 7 | + | 2 (13%) | 3 (5%) | 3 (9%) 8 | 8 | + | | 4 (7%) | 2 (6%) 8 | 7 | - | | 1 (2%) | 14 (41%) --------+----------+-----------------+---------+------------+-----------

Ventrally, the bony carapace shows ten thoracic vertebrae, the second through the ninth having well-developed, depressed ribs that are fused (no sutures) to the pleurals. The ribs of the first thoracic vertebra are represented by bony struts that extend posterolaterally and contact the anterior borders of the second pair of ribs. The two ribs of the ninth pair are free for most of their length and often are broken; they are slightly shorter than the eighth pair of ribs. The ribs of the tenth thoracic vertebra may be well-developed (KU 2219, 2666, 50856, _spinifer_, and 16528, _ferox_), but are usually broken off and represented only by transverse processes.

Kyphosis

Kyphosis (angular curvature of the vertebral column) or the hump-backed condition in American softshell turtles has been summarized by Nixon and Smith (1949:28). Cahn (1937:185, pl. 25e) illustrated the condition in an individual of _T. spinifer_, and H. M. Smith (1947:119) mentioned kyphotic softshells representing the species _spinifer_ (subspecies _hartwegi_ and _emoryi_) and _muticus_. Neill (1951:10) mentioned two kyphotic _T. s. asper_ and Nixon and Smith (_loc. cit._) recorded the report of a kyphotic _T. ferox_. I have noted the condition in four _muticus_ (subspecies _muticus_, KU 1959-60, 23230; INHS 2148) and seven _spinifer_ (CNHM 22925; subspecies _hartwegi_, USNM 55689; subspecies _spinifer_, UMMZ 52948, 95615; subspecies _emoryi_, KU 2219, 33523, TU 16240). The smallest kyphotic specimen, a hatchling, TU 16240, has a plastral length of 3.5 centimeters. Kyphosis is to be expected in all kinds of softshells as are other abnormalities, such as albinism (reported for _Lissemys_ by D'Abreu, 1928, and partial albinism noted in _T. cartilagineus_ by Mohr, 1929) or congenital absence of limbs (reported by Dutta, 1931, as occurring in the genera _Trionyx_ and _Lissemys_). The cause of kyphosis is not known. Smith (_op. cit._:120) suggested an abnormally early fusion of the costals (= pleurals) with the ribs, and a subsequent differential rate of growth between them and the vertebral column as a hypothesis; Williams (1957:236) proposed that late retraction of the yolk mass, or retraction of an excessively large yolk mass may cause kyphosis. The cause of kyphosis may be of genetic origin or due to some environmental damage to the vertebral column prior to the cessation of growth. The variation in rate of growth of the vertebral column may produce humps of different shapes and sizes. Some of the specimens noted above (UMMZ 52948, 95615) have the carapace only slightly arched and are considered partly kyphotic. There seem to be degrees of kyphosis, a fact that should be taken into account in considering the occurrence of variation in greatest depth of shell.

Plastron

The plastron is united to the carapace by ligamentous tissue and is somewhat flexible anteriorly and posteriorly. Anteriorly the plastron is somewhat hingelike and may contact the anteriormost edge of the carapace. The bony elements are reduced. There is usually a median vacuity, which is relatively smaller in larger specimens and may be divided into two vacuities (a posteromedial and an anteromedial) by the medial juxtaposition of the hyo-hypoplastra, especially in _muticus_. Williams and McDowell (1952) have recommended a change in nomenclature for some of the plastral bones on the basis of reinterpretation of their homologies. The nine plastral bones include: an anterior pair of preplastra (= epiplastra, _auct._); an unpaired, median bone, representing fused epiplastra (= entoplastron, _auct._), hereafter referred to as the epiplastron; a pair of hyoplastra; a pair of hypoplastra; and, posteriorly, a pair of xiphiplastra (Fig. 17).

Siebenrock's (1902) synopsis of living trionychids was based entirely on plastral characters. He distinguished between _muticus_ and _spinifer_ principally by the shape of the epiplastron; _T. ferox_ was not considered different from _spinifer_. The median angle formed by the boomerang-shaped epiplastron is obtuse and somewhat greater than 90 degrees in _muticus_ (Fig. 17a); the angle of the epiplastron in _spinifer_ and _ferox_ is smaller than in _muticus_ and forms an approximate right angle (Fig. 17b). Williams and McDowell (_op. cit._:277, Pl. 1, Fig. 3) presented an illustration of the anterior plastral elements of an adult _T. ferox_. Siebenrock provided illustrations of the plastrons of _muticus_ (_op. cit._:823, Fig. 5) and _spinifer_ (_op. cit._:830, Fig. 10).

Much importance has been credited to the fusion (no suture) or separation (suture present) of the hypoplastra and hyoplastra. The fusion of these bones distinguishes the genera _Lissemys_, _Cyclanorbis_ and _Cycloderma_ from _Trionyx_, _Pelochelys_, and _Chitra_ (Siebenrock, _op. cit._:815, 817; Loveridge and Williams, 1957:415). This character is also one of the criteria used by Hummel (1929: 768) in his erection of the two subfamilies Cyclanorbinae (= Lissemyinae) and Trionychinae. In my examination of specimens this character, unfortunately, was not given full attention. I have noted the fusion of the hypoplastra and hyoplastra in KU 1878 (_muticus_, right side only), KU 2219 (kyphotic _spinifer_), KU 16528 (_ferox_) and KU 60121 (_ferox_). Dr. Ernest E. Williams informs me in a letter of November 17, 1959, that of six specimens of _ferox_ in the MCZ, the hyoplastra are fused with the hypoplastra in three (54689-90, 54686). I suspect that these bones in the three American species of the genus _Trionyx_, especially in _ferox_, fuse more often than is supposed.

In _muticus_ the constricted part of the hyoplastron and hypoplastron is wider anteroposteriorly than in _spinifer_ or _ferox_ (Fig. 17).

The three American species have on the hyoplastra, hypoplastra, and xiphiplastra well-developed callosities, which enlarge with increasing size. The medial borders of the hyoplastral and hypoplastral callosities in larger specimens are rounded and closely approximated, often touching, as do the callosities of each xiphiplastron; seemingly, the callosities are relatively larger in _muticus_ than in _spinifer_ and _ferox_. I have seen one adult male _muticus_ (KU 41380) that lacked median fontanelles or vacuities owing to the contact of the plastral elements (as viewed through overlying skin, alcoholic specimen). The bony plastron (approximately 9 cm. in maximal length) of a small _muticus_ (KU 19460) resembles the plastron of larger individuals of _muticus_ in having well-developed hyoplastral and hypoplastral callosities that are closely approximated medially. Large individuals of _muticus_ usually have small, ovoid callosities on the preplastra, and a well-developed, angular callosity on the epiplastron (Fig. 17a). Siebenrock (_op. cit._:823) suggests that the presence of callosities on the preplastra and epiplastron of _muticus_ is subject to individual variation. I can not substantiate or dispute the supposition of Baur (1888:1122), Siebenrock (1924:193) and Stejneger (1944:12, 19) that the callosities are larger in males of _muticus_ than in the females. Some individuals of _spinifer_ have seven plastral callosities (KU 2842) as does _muticus_, but the callosities on the preplastra and epiplastron are less frequent and less well-developed in large specimens of _spinifer_ than in _muticus_. The small epiplastral callosity in _spinifer_ is located at the medial angle and does not extend posterolaterally to cover the entire surface of the epiplastron as it may in _muticus_ (Fig. 17b). The epiplastron of a _spinifer_ (KU 2826) has a medial callosity and another on the right posterolateral projection; three separate callosities occur on the epiplastron of MCZ 46615. The last specimen mentioned, a large, stuffed female, possesses a round, intercalary bone that tends to occlude the posteromedial vacuity. Seemingly, the callosity on the epiplastron appears prior to those on the preplastra; I have not seen any plastra having callosities on the preplastra and lacking a callosity on the epiplastron. I have not noted callosities on the preplastra or epiplastron of specimens of _ferox_.

The callosities on the plastral bones are sculptured; small, recently formed callosities on the preplastra and epiplastron lack sculpturing. The pattern of sculpturing on the plastral bones as well as that of the carapace is generally of anastamosing ridges. I am unable to discern any differences in pattern of sculpturing between the three American species. Stejneger distinguished adult specimens of _ferox_ from the other American species by the coarseness of the sculpture of the bony callosities (1944:24) and of the bony carapace (_op. cit._:32). The sculpturing on the plastral callosities and carapace seems to be correlated with size; larger specimens (_ferox_) have coarser sculpturing than do smaller specimens (_muticus_). Stejneger also mentioned that the sculpturing on many specimens of _ferox_ is specialized into prominent, longitudinal welts (_loc. cit._); these welts occur also on the carapace of _spinifer_.

On the basis of the osteological characters examined by me, _T. muticus_ is distinguished from _spinifer_ and _ferox_ by a number of characters (plastron and especially skull) whereas the species _spinifer_ and _ferox_ are not easily distinguished from one another.

Composition of the Genus _Trionyx_ in North America

Analysis of the characters previously mentioned and their geographic distribution permits the recognition of ten taxa, comprising four species and eight subspecies. Two subspecies, _T. spinifer_ pallidus and _T. s. guadalupensis_ are described as new. The four species and the included subspecies here recognized are:

_Trionyx ferox_ _Trionyx spinifer spinifer_ _hartwegi_ _asper_ _emoryi_ _guadalupensis_ _pallidus_ _Trionyx ater_ _Trionyx muticus muticus_ _calvatus_

The following key is designed to permit quick identification of living individuals; therefore, ratios and osteological characters are avoided as much as possible in favor of other characters that are the least variable and most "typical." Because there is considerable variation correlated with sex and size, each taxon occurs in the key in more than one couplet. Large females having mottled and blotched patterns will be the most difficult to identify. The characters listed should be used in combination because one character alone may not be sufficient; it is advisable to read both choices of each couplet. The text, figures and illustrations should be consulted for final identification.

ARTIFICIAL KEY TO NORTH AMERICAN SPECIES AND SUBSPECIES OF THE GENUS TRIONYX

1. Septal ridges present; tubercles on anterior edge of carapace present or absent 2

Septal ridges absent; anterior edge of carapace lacking tubercles or raised prominences 19

2. Plastral area a uniform dark slate or blackish; soft parts of body blackish having large pale marks dorsally; carapace having large black blotches, often fused along margin, on pale background, and many well-defined longitudinal ridges _ T. ferox_, p. 479

Combination of characters not as above; ventral surface whitish, blackish flecks or blotches sometimes present 3

3. Carapace having pattern of white dots, or black ocelli and/or spots; carapace sometimes gritty resembling sandpaper 4

Carapace uniform pale brownish or grayish, or having mottled and blotched pattern, contrasting or not; white dots or tubercles, black ocelli and/or spots may be present; carapace not gritty 10

4. Carapace having pattern of black ocelli and/or spots; numerous, conspicuous whitish spots or tubercles absent 5

Carapace having pattern of white dots that are sometimes surrounded by small black ocelli; small black dots may be interspersed among larger white dots 7

5. Carapace having two or more marginal lines, these often diffuse and interrupted; black spots sometimes ocellate or bacilliform, or interspersed among smaller black dots; postocular and postlabial stripes usually united _spinifer asper_, p. 502

Carapace having only one dark marginal line; pattern of black ocelli or spots; postocular and postlabial stripes usually not united 6

6. Carapace having prominent ocelli, which are much larger near the center than at the sides _spinifer spinifer_, p. 489

Carapace having numerous small, dark spots, sometimes small ocelli, which are not much larger near the center than the sides _spinifer hartwegi_, p. 497

7. White spots on anterior third of carapace; white spots on carapace often surrounded by narrow blackish ocelli; small black dots sometimes interspersed among white spots _spinifer guadalupensis_, p. 517

White spots absent on anterior third of carapace, or small and inconspicuous; white spots not surrounded by narrow blackish ocelli 8

8. Pale rim of carapace narrow, partly obscured; over-all dorsal coloration (including soft parts of body) dark and lacking pattern; few, small, white tubercles confined to posterior third of carapace _ater_, p. 528

Pale rim distinct, without markings; soft parts of body dorsally not uniformly dark; many white tubercles usually contrasting on pale carapace 9

9. White spots confined to posterior third of carapace; ground color of carapace usually pale brown or tan, sometimes darker; a dark, slightly curved, line connecting anterior margins of orbits; postocular stripe usually interrupted leaving pale, blotch behind eye; pale rim of carapace four or five times wider posteriorly than laterally _spinifer emoryi_, p. 510

Small white spots on posterior half of carapace gradually decreasing in size anteriorly, often indistinct or absent on anterior third of carapace; pale rim of carapace no more than three times wider posteriorly than laterally _spinifer pallidus_, p. 522

10. Marginal ridge present; carapace having ill-defined dark blotches on uniform grayish, lacking whitish tubercles or well-defined black spots or ocelli; pale rim of carapace absent; tubercles on anterior edge of carapace resembling flattened hemispheres; anterior parts of plastron often visible in dorsal view; postocular stripe, if present, having thick, blackish borders _ferox_, p. 479

Marginal ridge absent 11

11. Carapace uniform pale brownish, lacking mottled and blotched pattern, white dots, black ocelli or spots 12

Carapace having mottled and blotched pattern, contrasting or not; white spots or tubercles, black ocelli or spots may be present 13

12. Pale rim of carapace four or five times wider posteriorly than laterally; dark, straight or slightly curved, line connecting anterior margins of orbits _spinifer emoryi_, p. 510

Pale rim of carapace no more than three times wider posteriorly than laterally _spinifer pallidus_, p. 522

13. Rear margin of carapace usually roughened by fine corrugations, edge often ragged; pale rim absent; carapace having dark brown-blackish, mottled and blotched pattern; anterior edge of carapace more or less smooth having scarcely elevated prominences; posterior part of plastral area and especially ventral surface of carapace having numerous black marks _ater_, p. 528

Rear margin of carapace smooth, edge entire; usually some evidence of pale rim 14

14. White, rounded tubercles or spots usually evident posteriorly on carapace, sometimes indistinct; black ocelli or spots lacking in center of carapace, sometimes present at sides; shape of tubercles on anterior edge of carapace variable 15

White spots or tubercles absent; margin of carapace usually having black ocelli or spots; tubercles on anterior edge of carapace equilateral or conical, not low and flattened 17

15. White spots often present on anterior half of carapace; tubercles on anterior edge equilateral and wartlike, or less elevated, not conical _spinifer guadalupensis_, p. 517

White spots usually absent on anterior half of carapace, sometimes indistinct; shape of tubercles on anterior edge of carapace variable 16

16. White spots absent on anterior half of carapace; tubercles on anterior edge of carapace low, scarcely elevated, never equilateral or conical; mottled and blotched pattern often not contrasting; ground color of carapace sometimes dark; pale rim of carapace four or five times wider posteriorly than laterally; dark, straight or slightly curved, line connecting anterior margins or orbits _spinifer emoryi_, p. 510

White spots sometimes indistinct on carapace, or few, small spots present on posterior half of carapace; tubercles on anterior edge of carapace equilateral and wartlike or conical; mottled and blotched pattern usually contrasting; pale rim less than three times wider posteriorly than laterally _spinifer pallidus_, p. 522

17. Carapace having evidence of more than one dark marginal line, and scattered, black spots or ocelli _spinifer asper_, p. 502

Carapace having only one, dark, marginal line 18

18. Carapace having small black spots, lacking large interrupted ocelli _spinifer hartwegi_, p. 497

Carapace having small black spots interspersed among larger, interrupted ocelli _spinifer spinifer_, p. 489

19. Carapace having pattern of dusky spots, sometimes short lines 20

Carapace lacking pattern of dark spots or lines, having a mottled and blotched pattern 21

20. Pattern of circular spots, lacking short lines or bacilliform marks; spots sometimes slightly ocellate; no pale stripes on snout _muticus calvatus_, p. 539

Pattern of dots, or dots and short lines; pale stripes on snout, at least just in front of eyes _muticus muticus_, p. 534

21. Mottled and blotched pattern usually contrasting; ill-defined, blackish blotch absent behind eye _muticus muticus_, p. 534

Mottled and blotched pattern usually not contrasting; ill-defined, dark blotch may be present behind eye _muticus calvatus_, p. 539

Systematic Account of Species and Subspecies

=Trionyx ferox= (Schneider)

Florida Softshell

Plates 31 and 32

_Testudo ferox_ Schneider, Naturg. Schildkr., p. 330, 1783 (based on Pennant, Philos. Trans. London, 61 (Pt. 1, Art. 32): 268, pl. 10 [figs. 1-3], 1772).

_Trionyx ferox_ Schwartz, Charleston Mus. Leaflet, No. 26:17, pls. 1-3, May, 1956.

_Testudo mollis_ Lacépède, Hist., Nat. Quadr. Ovip. Serp., 1:137, pl. 7, 1788.

_Testudo_ (_ferox_?) verrucosa Schoepff, Hist. Testud., Fasc. 5 (Plag. M):90, pl. 19, 1795.

_Testudo bartrami_ Daudin, Hist. Nat. Rept., 2:74, pl. 18, fig. 2, 1801.

_Trionyx georgicus_ Geoffroy, Ann. Mus. Hist. Nat., Paris, 14:17, August, 1809.

_Mesodeca bartrami_ Rafinesque, Atlan. Jour., Friend Knowledge, Philadelphia, 1 (No. 2, Art. 12):64, Summer, 1832.

_Trionyx harlani_ Bell in Harlan, Medic. Phys. Research, p. 159, 1835.

_Type._--Holotype, British Museum (Natural History) 1947.3.6.17; original number 53A, presumably that of Royal Society; stuffed adult female and skull; obtained from the Savannah River, Georgia, by Dr. Alexander Garden.

_Range._--Southern South Carolina, southeastern Georgia, and all of Florida except the Keys and perhaps the western end of the panhandle (see map, Fig. 18).

_Diagnosis._--Marginal ridge present; longitudinal rows of tubercles that resemble ridges on carapace of hatchlings; plastron often extending farther forward than carapace in adults; plastral area dark slate or gray in hatchlings; juvenal pattern of large slate or blackish blotches (often with pale centers) on a pale background; pale outer rim of carapace (absent on adults) narrow, not separated from ground color of carapace by distinct, dark line.

Size large; head wide; carapace relatively long and narrow; snout short; greatest width of skull at level of quadratojugal; often no suture between hypoplastra and hyoplastra; callosities on epiplastron and preplastra usually lacking.

_Description._--Plastral length of smallest hatchling, 2.9 centimeters (UMMZ 95613), of largest male, 26.0 centimeters (AMNH 63642), of largest female, 34.0 centimeters (UMMZ 38123).

Septal ridges present; over-all coloration of carapace and plastron, and soft parts of body of hatchlings slate or blackish; carapace having blackish, circular blotches, usually fused at margin, often with pale centers on buff background forming coarse reticulum; pale, narrow rim of carapace not separated from ground color by dark marginal line; pale rim, coincident with marginal ridge, absent from anteriormost nuchal region; longitudinal rows of tubercles on carapace resembling ridges; undersurface blackish, usually having posterior part of carapace pale with irregular blackish marks; blackish soft parts of body dorsally having large, pale markings, most consistent of which are postocular mark that may contact orbit, postlabial mark that curves around angle of jaws, inverted Y on top of snout, and one or two streaks on side of neck.

Over-all coloration of adults grayish, paler than in hatchlings; carapace gray sometimes having slightly darker, large, irregular markings; mottled and blotched pattern on females not contrasting; sex of many large individuals not distinguishable on basis of pattern on carapace; pale rim of carapace obscure or absent; soft parts of body dorsally gray or brownish on large adults of both sexes, sometimes having slightly paler, large markings; small adult males usually having contrasting pattern on head; surface of carapace smooth (not "sandpaper") on adult males; undersurface whitish, throat often grayish; well-defined marginal ridge; anterior edge of carapace laterally to region of insertion of forelimbs studded with low, flattened tubercles resembling hemispheres, never conical; carapace usually having blunted tubercles, best developed anteriorly and posteriorly on midline, but sometimes linearly arranged, resembling ridges, especially at margins; anterolateral parts of plastron often extending farther forward than corresponding parts of carapace.

Range in length (in cm.) of plastron of ten largest specimens of each sex (mean follows extremes), males, 17.0-26.0, 20.0; females 23.3-34.0, 27.9; ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 6.5 centimeters or less, 3.52, and exceeding 6.5 centimeters, 4.87; ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.0 centimeters or less, 1.18, and exceeding 8.0 centimeters, 1.30; mean CL/PCW, 2.01; mean HW/SL, 1.44; mean CL/PL, 1.26.

Jaws of some skulls that exceed 75 millimeters in basicranial length having expanded alveolar surfaces; greatest width of skull usually at level of quadratojugal (72%); ventral surface of supraoccipital spine narrow proximally, usually having medial ridge; foramen magnum rhomboidal; opisthotic-exoccipital spur absent (82%), sometimes indicated by ridge (16%); distal part of opisthotic wing tapered, not visible in dorsal view; lateral condyle of articular surface of quadrate larger than medial articular surface, not tapered posteriorly; maxillaries in contact above premaxillaries; usually a combination of seven neurals, seven pairs of pleurals, and contact of seventh pair of pleurals (56%), often eight pairs of pleurals (31%); angle of epiplastron forming approximate right angle; often no suture between hypoplastra and hyoplastra; callosities on preplastra and epiplastron usually lacking.

_Variation._--Crenshaw and Hopkins (1955:19) stated that in specimens from Lake Okeechobee and southward the carapace is wider relative to the width of the head, and Neill (1951:19) quoted Allen's observations that _ferox_ from southern Florida "average larger and darker than those collected farther north."

Carr (1952:417) reported that the pale reticulum on the carapace is yellowish olive, the markings on head are yellow on an olive ground color, some markings more orange, and the plastron slate gray. Duellman and Schwartz (1958:271) mentioned that the carapace of hatchlings is edged in orange grading to yellow posteriorly and has a pattern of bluish-black blotches on a dull brown background, whereas the carapace is dull brown or blackish on adults. Neill (_op. cit._:18) wrote "that the head stripes and the marginal ring of the 'carapace' are orange rather than yellow (yellow at the time of hatching, however)."

The transition from the dark coloration of hatchlings to the paler coloration of adults is gradual and subject to individual variation. The loss of dark color ventrally occurs first on the plastral area, then the hind limbs, forelimbs, posterior part of carapace and last on the neck and throat. The soft parts of the body dorsally are gray or dark gray, and do not become so pale as the ventral surface. The smallest specimen that I have seen displaying the dark features of the hatchlings is a male, 7.7 centimeters (UMMZ 100673); a female, 9.5 centimeters (UMMZ 110987), is the smallest specimen having a whitish plastral area. The change from dark to pale coloration on the ventral surface occurs at a size of 8.0 to 9.0 centimeters. The largest specimens I have seen having indistinct, dusky blotches of the underside of the carapace are a female, 11.3 centimeters (UMMZ 100836), and a male, 16.0 centimeters (UMMZ 106322). A contrasting pattern on head and limbs, and a dark throat are still evident in a female 19.2 centimeters (UMMZ 106302).

_Comparisons._--_Trionyx ferox_ can be distinguished from all other species of the genus in North America by the presence of a marginal ridge, longitudinal ridges of tubercles on the carapace of juveniles (less evident in adults), and the unique juvenal pattern and coloration. The lack of a juvenal pattern and a smooth surface on the carapace (not gritty like sandpaper) distinguish adult males from those of _T. spinifer_. Most adults of both sexes can be distinguished from _spinifer_ and _muticus_ by the extension of the plastron farther forward than the carapace (developed to a slight degree in some specimens of _T. s. emoryi_). Both sexes of all ages can be distinguished from _muticus_ by the presence of knoblike tubercles on the anterior edge of the carapace, and septal ridges.

_T. ferox_ is the largest species in North America; the maximum size of the plastron in adult males is approximately 26.0 centimeters (16.0 in _spinifer_) and of adult females, 34.0 centimeters (31.0 in _spinifer_). The head is wider in _ferox_ than in _muticus_ and most subspecies of _spinifer_ (closely approached by _asper_, _guadalupensis_, _emoryi_ and _T. ater_). The carapace is narrower in _ferox_ than in _muticus_ and most subspecies of _spinifer_ (closely approached by _emoryi_ and _T. ater_). The snout is shortest in _ferox_, but almost as short in _T. s. emoryi_ and _T. ater_. _T. ferox_ has proportionately the longest plastron in relation to length of carapace.

Most skulls of _ferox_ differ from those of _muticus_ and _spinifer_ in having the greatest width at the level of the quadratojugal (as do some _T. s. asper_; see account of that subspecies). In the skull, _ferox_ resembles _spinifer_ but differs from _muticus_ in having the 1) ventral surface of the supraoccipital spine narrow proximally, and usually having a medial ridge, 2) foramen magnum rhomboidal, 3) distal part of opisthotic wing tapered, 4) lateral condyle of articular surface of quadrate not tapered posteriorly, and larger than medial articular surface, and 5) maxillaries in contact above premaxillaries. _T. ferox_ resembles _muticus_ but differs from most individuals of _spinifer_ in lacking a well-developed opisthotic-exoccipital spur. _T. ferox_ resembles _spinifer_ but differs from _muticus_ in having the epiplastron bent at approximately a right angle; _ferox_ differs from both _muticus_ and _spinifer_ in lacking a callosity on the epiplastron and probably in the more frequent fusion of the hyoplastra and hypoplastra.

_Remarks._--The early taxonomic history of _Trionyx ferox_ has been discussed in detail by Stejneger (1944:27-32), who explained that Dr. Alexander Garden of Charleston, South Carolina, sent a description and specimen of _T. ferox_ to Thomas Pennant, and at the same time sent another specimen with drawings to a friend, John Ellis, in London. Pennant presented one of the specimens and drawings and the description to the Royal Society of London in 1771; the description was published in 1772 and included Garden's drawings. Because two specimens were involved the possibility exists that the description (text, drawings and type specimen) is a composite based on two specimens.

I have not seen the type. Garden's original description (_in_ Pennant, 1772:268-271) leaves little doubt that the text subject is a large adult female of _ferox_ (see especially the statements, "fore part, [of carapace] just where it covers the head and neck, is studded full of large knobs, [and] The under, or belly plate, ... is ... extended forward two or three inches more than the back plate, ..."). I am indebted to Mr. J. C. Battersby, British Museum (Natural History), Department of Zoology (Reptiles), for information concerning the type and for comparing it with the text description and three figures published by Pennant. The carapace of the type is approximately 16 inches long, 13-1/2 inches wide, and has low, flattened, knoblike tubercles along the anterior edge. Some inaccuracies on the part of the artist (such as five claws on both feet on the right side of Fig. 3, and four claws on the left front foot of Fig. 2 are evident), and slight changes in the proportions of the type would have occurred after death and preservation. It is the opinion of Mr. Battersby that the type, text description and three figures represent one specimen. Figures 1 and 2, dorsal and ventral views respectively, probably represent the same specimen from life; the neck is withdrawn and the tail tip is visible in dorsal view, but concealed beneath the posterior edge of the carapace in ventral view. Presumably the same specimen (probably drawn from dried and stuffed animal) is depicted in Figure 3 (dorsal view); the neck is fully extended and a large part of the thick, pyramidal tail is visible in dorsal view. British Museum (Natural History) 1947.3.6.17 is considered a holotype. The three figures published by Pennant have been duplicated by Schoepff (1795:Pl. 19) and Duméril and Bibron (1835:482). To my knowledge, the holotype was first specifically designated as the "(Type.)" of _T. ferox_ by Boulenger (1889:259). The skull of the holotype is figured by Stejneger (1944:Pl. 5).

Garden did not list a specific locality for the two specimens that he sent to London, but did mention that the turtle was common in the Savannah and Altamaha rivers (of Georgia), and rivers in east Florida. Boulenger (_loc. cit._) stated that the locality of the holotype was "Georgia." Baur (1893:220) restricted the type locality to the "Savannah river, Ga." Neill (1951:17), who believed _T. ferox_ to be absent from the Savannah River, changed the type locality of _ferox_ to east Florida. Schwartz (1956:8) reappraised the status of softshells in Georgia and Florida and reëstablished the Savannah River (at Savannah), Georgia, as the type locality of _T. ferox_.

Pennant failed to use binomial nomenclature when he published the type description of Garden. The first name-combination (_Testudo ferox_) was proposed by Schneider (1783:220).

Lacépède (1788:137, Pl. 7) referred to Garden's description in Pennant only as "The Molle" but on a folded paper chart entitled "Table Méthodique des Quadrupèdes ovipares," which is inserted after an introduction of 17 pages, listed _T. mollis_; this name is again listed on another folded chart, entitled "Synopsis methodica Quadrupedum oviparorum," which is inserted between pages 618 and 619 under the genus _Testudo_. The illustration (Pl. 7) was taken from Pennant (Duméril and Bibron, _loc. cit._). The type locality has been designated "(following Stejneger, 1944) as eastern Florida" by Schmidt (1953:108).

Bartram failed to use a binomial name with his description of "the great soft shelled tortoise," which appeared in his _Travels_ (1791:177-179, Pl. 4 and unnumbered plate between pages 282 and 283) and two editions of a French translation (1799 and 1801, 1:307); see Harper (1940). Recently, Bartram's _Travels_ has been placed on the Official Index of Rejected and Invalid Works in Zoological Nomenclature, Opinion 447 (see Hemming, 1957). Bartram's description of a soft-shelled turtle has provided the basis for the proposal of at least three name-combinations. The first was _Testudo_ (_ferox?_) _verrucosa_ proposed in 1795 by Schoepff; it appeared simultaneously in _The Historia Testudinum_ and in a German translation, _Naturgeschichte der Schildkröten_ (see Mittleman, 1944:245). Stejneger (1944:26) listed the type locality as eastern Florida. Daudin (1801:74), also referring to Bartram's description in his _Voyage_ (French translation), proposed the name _Testudo bartrami_; Harper (_op. cit._:717) restricted the type locality of _T. bartrami_ from "Halfway pond," east Florida, to southwestern Putnam County between Palatka and Gainesville, Florida. Rafinesque (1832:64-65), relying on the authenticity of the illustrations in Bartram's _Travels_ that depict a soft-shelled turtle having five claws on each of the hind feet, tubercles on the sides of the head and neck, and ten scales in the middle of the carapace (presumably inaccuracies or a composite on the part of the artist), referred to Bartram's description as a new genus, _Mesodeca bartrami_, a name which Boulenger (1889:245, footnote) referred to as "mythical." Geoffroy (1809a:18-19) considered Bartram's description the basis for the recognition of a second species of _Chelys_ (binomial nomenclature not employed), and Duméril and Bibron (_loc. cit._) suggested that the description was based partly on a "Chelyde Matamata." The descriptive comments of Bartram are not clearly applicable to _Testudo ferox_ Schneider; _Trionyx ferox_, however, is the only species of soft-shelled turtle known to occur in the region of Bartram's observations (east Florida), and the type locality was restricted to Putnam County, Florida, by Harper. The name-combinations, _Testudo___ (_ferox?_) _verrucosa_ Schoepff, _Testudo bartrami_ Daudin, and _Mesodeca bartrami_ Rafinesque are junior synonyms of _Testudo ferox_ Schneider.

Schweigger (1812:285) referred _ferox_ to the genus _Trionyx_ following the description of that genus by Geoffroy in 1809. _Testudo ferox_ was listed as a synonym by Geoffroy in the description of _Trionyx georgicus_ (1809a:17); Duméril and Bibron (1835:432) mentioned that the specific characters of _georgicus_ were taken from Pennant. The name _Trionyx georgianus_ presumably appears for this taxon in Geoffroy's earlier-published synopsis (1809:367). _T. georgicus_ was listed as occurring in rivers of Georgia and the Carolinas; the type locality was restricted by Schmidt (_op. cit._:109) to the Savannah River, Georgia. The two specific names _georgicus_ and _georgianus_ are regarded as substitute names and junior synonyms of _T. ferox_.

Geoffroy (1809a:14-15) also described _Trionyx carinatus_, a name-combination that hitherto has been considered a synonym of _Trionyx ferox_. There is no indication from the description that _carinatus_ is applicable to _ferox_. Most comments pertain to a description of the bony carapace and plastron, which Geoffroy depicts in Plate 4. It is a young specimen judging from the small and isolated preneural; the seventh pair of pleurals is unusual in being fused (no middorsal suture), and the neurals seem large in proportion to the size of the pleurals. The anterior border of the carapace is described as having tubercles. Geoffroy listed _Testudo membranacea_ and _Testudo rostrata_ as synonyms of _carinatus_. Fitzinger (1835:127) listed _T. membranacea_, _T. rostrata_ and _T. carinatus_ as synonyms of _Trionyx javanicus_ (= _T. cartilagineus_), which was also described by Geoffroy (_op. cit._:15). Duméril and Bibron (_op. cit._:478, 482) considered _carinatus_ to be the young of _spinifer_ (_ferox_ as synonym). Gray (1844:48), however, referred _T. membranacea_ and _T. rostrata_ to the synonymy of _T. javanicus_, but considered _T. carinatus_ to be a synonym of _T. ferox_ (_op. cit._:50), an interpretation followed by all subsequent authors. _Trionyx carinatus_ is questionably listed as a synonym of _ferox_ by Stejneger (1944:27). Duméril and Bibron (_op. cit._:482) wrote that the young type of _carinatus_ is in the museum at Paris. Dr. Jean Guibé informs me in letter of September 24, 1959, that the type of Geoffroy's _T. carinatus_ cannot be found in the Natural History Museum at Paris. For the present, _T. carinatus_ is considered a _nomen dubium_. According to Stejneger (1944:27), _Trionyx brongniarti_ Schweigger is a substitute name for _T. carinatus_.

I am unable to add anything to Stejneger's (_op. cit._:32) account of _Trionyx harlani_; the mention of its occurrence in east Florida indicates that it is indistinguishable from _Testudo ferox_ Schneider.

_T. ferox_ was considered to be indistinguishable from Lesueur's _Trionyx spiniferus_ (described in 1827), until Agassiz (1857:401) pointed out the differences between the two species. However, Agassiz (_op. cit._:402, Pl. 6, Fig. 3) regarded juveniles of _T. spinifer asper_ as the young of _ferox_. Consequently, the geographic range of _ferox_, as envisioned by Agassiz, extended from Georgia and Florida west to Louisiana. Neill (1951:15) considered all American forms conspecific. Crenshaw and Hopkins (1955) and Schwartz (1956) demonstrated that _ferox_ is a distinct species.

Fitzinger (1843:30) designated the species _ferox_ as the type species of his genus _Platypeltis_ as follows: "Platypeltis. Fitz. Am[erica]. _Platypelt. ferox_. Fitz. Typus." If populations of soft-shelled turtles that are referable to _Testudo ferox_ Schneider are considered to comprise a distinct genus by future workers, _Platypeltis_ Fitzinger, 1835, is available as a generic name with _Testudo ferox_ Schneider, 1783, as the type species (by subsequent designation).

_Trionyx ferox_ in the northern part of its range is sympatric with _T. spinifer asper_. In the region of overlap, the two species are nearly always ecologically isolated; _ferox_ inhabits lentic waters, whereas _T. s. asper_ is partial to lotic waters (Crenshaw and Hopkins, _op. cit._:16). There is no evidence of intergradation or hybridization.

Many characters of _Trionyx ferox_ that are lacking in other North American forms are shared with some Asiatic softshells, such as the large size, longitudinal rows of tubercles that resemble ridges on the carapace, and the marginal ridge. It is thought that, of the living softshells in North America, _ferox_ is more closely allied to Old World forms of the genus than to _muticus_ or _spinifer_.

Carr (1940:107) recorded _ferox_ from Okaloosa County, Florida, in the western end of the panhandle, whereas Crenshaw and Hopkins (1955:16) list the known westward extent of range as Leon and Wakulla counties. AMNH 6933 from west of the Apalachicola drainage in Washington County, Florida, tends to substantiate Carr's record, which is not included on the distribution map.

_Specimens examined._--Total 144, as follows: FLORIDA: _Alachua_: UMMZ 64178, 100969; USNM 10545, 10704, "near" Gainesville; UMMZ 56599, Levy Lake. _Brevard_: AMNH 12878, Canaveral. _Broward_: UMMZ 109441, Hugh Taylor Birch State Park; USNM 109548, 22 mi. WNW, 6 mi. SSE Fort Lauderdale. _Collier_: USNM 86828, Tamiami Trail, "near" Birdon. _Dade_: AMNH 50936, UMMZ 10183, 110981, Miami; USNM 84079, 86942, 15 mi. from (west) Miami, Tamiami Trail; UMMZ 111371, 19 mi. W, 1.3 mi. S Miami; UI 28984, 35 mi. W. (Miami) Tamiami Trail; AMNH 69932-33, UMMZ 101582, 101584, 104024, 40-45 mi. W Miami, Tamiami Trail. _Glades_: UMMZ 100836, mouth of Kissimmee River. _Hendry_: UMMZ 106302, 10.2 mi. SE Devil's Garden; UMMZ 106303-04, 106321-22, 30 mi. S Clewiston, near Devil's Garden. _Hernando_: TU 13624, 0.5 mi. S Citrus Co. line on US Hwy. 19. _Highland_: AMNH 65537, 71618, Archbold Biol. Stat., Lake Placid; AMNH 65622, Hicoria. _Hillsborough_: TU 13960, Hillsborough River, _ca._ 20 mi. NE Tampa; USNM 51184, Tampa; USNM 71156, Plant City. _Indian River_: USNM 55316, Vero Beach; USNM 59318, Sebastian. _Lake_: UMMZ 36072, USNM 20189, 029210, 029339, 38123, Eustis; UMMZ 76754-56, Lake Griffin. _Lee_: UMMZ 102276, 14 mi. SE Punta Gorda. _Leon_: CNHM 33701, USNM 95767, Lake Iamonia; USNM 103736, Silver Lake. _Marion_: AMNH 8294-95, UMMZ 95613 (4), USNM 52476-83, 100902-04, Eureka; AMNH 63642, near Salt Springs. _Martin_: TNHC 1292, 8.4 mi. N Port Mayaca. _Okeechobee_: AMNH 57379-84, Lake Okeechobee; AMNH 5931-32, Kissimmee Prairie. _Orange_: USNM 51421, 56805, Orlando; KU 16528. _Osceola_: USNM 029448, 029450-64, 029467-68, 029470, 029474-75, Kissimmee. _Palm Beach_: UMMZ 54101, Palm Beach; USNM 73199, Delray Beach. _Pinellas_: USNM 51417-20, St. Petersburg. _Polk_: AMNH 25543, Lakeland; UMMZ 112380, 6.7 mi. S Lake Wales; USNM 60496, 60532, 60534, 61083-87, Auburndale. _Putnam_: USNM 4373, 7651, Palatka; USNM 26035, ponds "near" Welaka. _Sarasota_: USNM 61352, Lake Myakka. _Sumpter_: UMMZ 71791, Bushnell. _Volusia_: UMMZ 100673, Lake Helen. _Washington_: AMNH 6933, Washington. _County unknown_: AMNH 4758; USNM 8899, St. John's River: USNM 59727-28, Lake Okeechobee, "near" mouth Taylor's Creek; USNM 84080.

GEORGIA: _Baker_: SM 2083, USNM 029619, 38980-81, 70398, Mimsville. _Berrien_: USNM 62217, Banks Mill Pond. _Charlton_: AMNH 69934, Okefinokee Swamp, SW Billy's Island; UMMZ 90010, east edge Okefinokee Swamp; USNM 84603, Okefinokee Swamp, Chesser's Island. _Irwin_: USNM 56804. _Lowndes_: UMMZ 67706, 10 mi. S Valdosta. _McIntosh_: USNM 19621, Darien.

SOUTH CAROLINA: _Charleston_: USNM 9670, Charleston.

NO DATA: AMNH 22750; USNM 71608-09.

_Records in the literature._--FLORIDA: _Alachua_: 10 mi. ENE Gainesville (Schwartz, 1956:18). _Brevard_: Merritt Island (Neill, 1958:6). _Broward_: Fort Lauderdale (Schwartz, _op. cit._:19). _Charlotte_: (Carr, 1940:107). _Clay_: Green Cove Springs (Brimley, 1910:18); St. John's River (Crenshaw and Hopkins, 1955:21); Doctor's Inlet (Schwartz, _op. cit._:18). _Collier_: Royal Palm Hammock (Crenshaw and Hopkins, _op. cit._:20); 11.2 mi. E Monroe Station (Schwartz, _op. cit._: 19). _Columbia_: (Carr, _loc. cit._). _Dade_: Paradise Key (Schwartz, _loc. cit._); Homestead (eggs, Stejneger, 1944:43). _Duval_: 4-10 mi. S Jacksonville (Deckert, 1918:31). _Glades_: _ca._ 8 mi. SW Okeechobee State Park. _Lake_: Alexander Springs (Schwartz, _op. cit._:18). _Lee_: 18 mi. S Fort Myers (Conant, 1930:63); 6 mi. SE Fort Myers (Hamilton, 1947:209). _Levy_: Gulf Hammock (Schwartz, _loc. cit._); Brownson (Stejneger, _op. cit._:42). _Monroe_ and _Okaloosa_ (Carr, _loc. cit._). _Okeechobee_: 6 mi. E Kissimmee River; state hwy. 78 "near" Okeechobee-Glades co. line. _Palm Beach_: SW part of Lake Okeechobee, near Clewiston; Milton Island Cove (Schwartz, _loc. cit._). _Pasco_: mouth Pithlachascotee River (Neill, _op. cit._:26). _Pinellas_: Belleair (Brimley, _loc. cit._); Seminole (Conant, _loc. cit._); 5 mi. E Clearwater (Schwartz, _op. cit._:19); Gulf Port (Stejneger, _op. cit._:43). _Polk_: Lake Shipp, near Winter Haven (Telford, 1952:185). _Sarasota_: 15 mi. E Sarasota (Conant, _loc. cit._); Venice (Conant, _op. cit._:61). _Taylor_: "near" Foley. _Wakulla_: "near" Crawfordville (Crenshaw and Hopkins, _op. cit._:15).

GEORGIA: _Baker_: 5 mi. NW Newton, 5 mi. W Newton, 4 mi. N Newton. _Ben Hill_: 6 mi. E Fitzgerald (Crenshaw and Hopkins, 1955:15). _Bulloch_: 14 mi. SE Statesboro (Schwartz, 1956:19). _Decatur_: "near" Bainbridge (Crenshaw and Hopkins, _loc. cit._). _Emanuel_: "near" Midville. _Evans_: 8 mi. NE Manassas, Tattnall County. _Ware_: Laura Walker State Park (Schwartz, _loc. cit._). _Wilcox_: 3 mi. SE Forest Glen (Crenshaw and Hopkins, _op. cit._:19).

SOUTH CAROLINA: _Beaufort_: 7 mi. NE Gardens Corner (Schwartz, 1956:19). _Chatham_: Savannah River at Savannah (Schwartz, _op. cit._:8-9). _Colleton_: 5 mi. from Whitehall, Combahee River (Schwartz, _op. cit._:19).

=Trionyx spinifer= Lesueur

Spiny Softshell

_Range._--In Canada, southern Ontario and Quebec; in the United States, northwestern Vermont and western New York south to northern Florida, east to central Montana, eastern Wyoming and Colorado, and New Mexico; introduced into the Colorado River system of California, Nevada, Arizona and New Mexico; in México, the northern part of the states of Tamaulipas, Nuevo León, Coahuila, and eastern Chihuahua (see map, Fig. 19).

_Diagnosis._--Juvenal pattern uniform tan or brownish lacking markings, having whitish dots or spots, or having well-defined, blackish ocelli or spots; surface of carapace "sandpapery" in adult males; conical projections (in some subspecies) along anterior edge of carapace in large females; contrasting pattern of blackish marks on pale background (in some subspecies) on dorsal surface of limbs of adult males.

Opisthotic-exoccipital spur well-developed; epiplastral callosity, when present, not covering entire surface.

_Description._--Septal ridges present; external and proportional characteristics variable (see accounts of subspecies); range in length of plastron (cm.) of ten largest specimens of each sex (mean follows extremes), males, 13.8-16.0, 14.4; females, 26.0-31.0, 28.0.

Greatest width of skull usually at level of squamosal (74%); foramen magnum rhomboidal; ventral surface of supraoccipital spine narrow proximally, usually having medial ridge; opisthotic-exoccipital spur well-developed (66%); distal part of opisthotic wing tapered, not visible in dorsal view; lateral condyle of articular surface of quadrate larger than medial articular surface, not tapered posteriorly; maxillaries in contact above premaxillaries (88%); usually a combination of seven neurals, seven pairs of pleurals and contact of seventh pair of pleurals (83%); angle of epiplastron approximately 90 degrees; callosities when present on epiplastron not covering entire surface; hyo-hypoplastral suture usually present.

_Comparisons._--_Trionyx spinifer_ can be distinguished from _T. ferox_ and _T. muticus_ by the presence of any one of the characters mentioned in the "Diagnosis." Both sexes and all sizes of _T. spinifer_ resemble _ferox_ but differ from _muticus_ in having septal ridges. Most individuals of _T. spinifer_ (except some large females) resemble _muticus_ but differ from _ferox_ and large females of _ater_ in having a pale outer rim that is separated from the ground color of the carapace by a distinct (_spinifer_) or dusky (_muticus_) dark line. Large females of the subspecies _spinifer_, _hartwegi_, _asper_ and _pallidus_ may have enlarged conical projections along the anterior edge of the carapace and, unless these projections are considerably worn, are readily distinguished from large females of _ferox_ (flattened, knoblike prominences), and _muticus_ and _ater_ (smooth surface, no prominences). Large females of the subspecies _guadalupensis_ and _emoryi_ resemble _muticus_ and _ater_, and to some extent _ferox_, in having low, scarcely elevated prominences along the anterior edge of the carapace. Some females of _emoryi_ resemble _ferox_ in that the plastron extends farther forward than the carapace.

_T. spinifer_ is intermediate in size between _ferox_ (larger) and _muticus_ (smaller); the maximum size of the plastron in adult males is approximately 16.0 centimeters (14.0, _muticus_; 26.0, _ferox_), and of females, 31.0 centimeters (21.5, _muticus_; 32.5, _ferox_). The head for all subspecies of _spinifer_ is proportionately narrower than in _ferox_ but wider than in _muticus_.

In the skull, _spinifer_ more closely resembles _ferox_ than _muticus_, but differs from both _ferox_ and _muticus_ in usually having a well-developed opisthotic-exoccipital spur. Skulls of _spinifer_ resemble those of _muticus_ but differ from those of _ferox_ in being widest at the level of the squamosal. Skulls of _spinifer_ resemble those of _ferox_ but differ from those of _muticus_ in having the 1) ventral surface of the supraoccipital spine narrow proximally, and usually having a medial ridge, 2) foramen magnum rhomboidal, 3) distal part of opisthotic wing tapered, 4) lateral condyle of articular surface of quadrate not tapered posteriorly, and larger than medial articular surface, and 5) maxillaries in contact above premaxillaries. _T. spinifer_ resembles _ferox_ but differs from _muticus_ in having the epiplastron bent at an approximate right angle. _T. spinifer_ differs from _ferox_ in having an epiplastral callosity, and from _muticus_ in that the callosity does not cover the entire surface of the epiplastron. The hyo-hypoplastral suture is present more often in _spinifer_ and _muticus_ than in _ferox_.

_Remarks._--Gray (1869:221) proposed the generic name _Callinia_ as a new name for _Aspidonectes_ as understood by Agassiz (1857:403). Gray referred _Trionyx spiciferus_ (= _spiniferus_) Lesueur to _Callinia_. Stejneger (1907:514) designated _Trionyx spiniferus_ Lesueur as the type species of _Callinia_. If _Trionyx spiniferus_ Lesueur is considered to be generically distinct from other soft-shelled turtles, _Callinia_ Gray, 1869, is available as a generic name with _Trionyx spiniferus_ Lesueur, 1827, as the type species by subsequent designation.

_Geographic variation._--_T. spinifer_ is the most variable and widespread species of the genus in North America. Size of ocelli on the carapace decreases from east to west on turtles inhabiting waterways of the Upper Mississippi River drainage. The most impressive gradient, geographically oriented from western Louisiana to southwestern Texas is seen in each of several features: decrease in size of tubercles on the anterior edge of the carapace, reduction in contrast of pattern on the dorsal surface of limbs and side of head, change in pattern on the dorsal surface of the snout, and increase in the size of white spots on the carapace. But the gradient in size of white spots is reversed in _T. s. emoryi_, which has small white spots on the carapace. Some of the characters at the western terminus of this geographical gradient are shared with _T. ater_ and _muticus_. Those subspecies comprising the _emoryi_ group also show proportional characters that correspond closely with those of _T. ferox_.

On the basis of tuberculation and pattern on carapace, side of head, dorsal surface of limbs and snout, _Trionyx spinifer_ may be divided into six subspecies.

=Trionyx spinifer spinifer= Lesueur

Eastern Spiny Softshell

Plates 33, 34, and 52

_Trionyx spiniferus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:258, pl. 6, December, 1827.

_T[rionyx] s[pinifer] spinifer_ Schwartz, Charleston Mus. Leaflet, No. 26:11, May, 1956.

_Trionyx ocellatus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:261, December, 1827.

_Apalone hudsonica_ Rafinesque, Atlan. Jour., Friend Knowledge, Philadelphia, 1(No. 2, Art. 12):64, Summer, 1832.

_Trionyx annulifer_ Wied-Neuwied, Riese Nord-Amerika, 1(pt. 3):140, 1838.

_Tyrse argus_ Gray, Cat. Tort. Croc. Amphis. Brit. Mus., p. 48, 1844.

_Aspidonectes nuchalis_ Agassiz, Contr. Nat. Hist. United States, 1(pt. 2):406, 1857.

_?G[ymnopus] olivaceus_ Wied-Neuwied, Nova Acta Acad. Leopold.-Carol., 32:55, pl. 5, 1865.

_Type._--Lectotype, Museum d'Histoire Naturelle, Paris, No. 8808; large stuffed female obtained by C. A. Lesueur from the Wabash River, New Harmony, Posey County, Indiana (Pl. 52).

_Range._--Northeastern United States and extreme southeastern Canada in tributaries flowing into the Mississippi River from the east, and the St. Lawrence River drainage; extreme southern Quebec and Ontario, Canada, east through southern Great Lakes region to Wisconsin, and south through New York, western Pennsylvania and Illinois to Tennessee and western Virginia (see map, Fig. 19).

_Diagnosis._--Juvenal pattern of large, thick-bordered black ocelli, often 9-10 millimeters in diameter in center of carapace on adult males, and 2-3 millimeters in diameter on hatchlings (mean OD/PL, Michigan, .066); only one dark marginal line separating pale rim of carapace from dorsal ground color.

_Description._--Plastral length of smallest hatchling, 2.7 centimeters (UMMZ 89950, INHS 3143); of largest male, 14.5 centimeters (UMMZ 72512); of largest female, 31.0 centimeters (UMMZ 40866).

Carapace olive, having large ocelli in center but smaller ocelli or spots at sides; ocelli often interrupted; pale rim of carapace not four or five times wider posteriorly than laterally, separated from darker ground color of carapace by one dark marginal line; large females often having remnants of ocelli at sides of carapace on mottled and blotched background; pattern on snout of pale, dark-bordered stripes that unite forming acute angle in front of eyes; well-defined dark markings in subocular and postlabial region; pattern contrasting with ground color on side of head; postlabial stripe interrupted, diffuse; pale postocular stripe having blackish borders interrupted, not uniting with postlabial stripe; dorsal surface of soft parts of body having contrasting pattern, largest blackish marks on hind limbs; elongate tail of adult males having pale dorsolateral bands with well-defined lower blackish borders; underparts whitish, often having blackish marks, except in center of plastral area; dark marks on webbing of limbs, palms and soles; dark streaks often coincident with digits; small conical tubercles on anterior edge of carapace on adult males; conical or equilateral tubercles on anterior edge of carapace of large females; accessory knoblike tubercles in nuchal region and in middle of carapace posteriorly on large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 7.0 centimeters or less, 4.09, and exceeding 7.0 centimeters, 5.50; ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.5 centimeters or less, 1.12, and exceeding 8.5 centimeters, 1.21; mean CL/PCW, 2.02; mean HW/SL, 1.30 (including subspecies _hartwegi_); mean CL/PL, 1.39.

_Variation._--Variant individuals include: UMMZ 72512, an adult male, having some ocelli seven millimeters in diameter that are almost solid spots; UMMZ 89659 having postocular and postlabial stripes connected on right side of head; UMMZ 95615, 52948, 54402 having inner dark borders of pale stripes on snout represented by short dashes and dots (a ragged line connecting anterior margins of orbits on 54402); UMMZ 52948, 89659 having interrupted, black marginal lines on carapace with ends of some segments oriented inward and overlapping portion of adjacent segments; UMMZ 81699, female having plastral length of 19.0 centimeters, lacking conspicuous tubercles on anterior edge of carapace; UI 2403, CNHM 92204 having extensive dark mottling and marbling on throat and neck, undersurface of limbs and posterior portion of carapace.

_Comparisons._--_T. s. spinifer_ can be distinguished from all other subspecies of _T. spinifer_ by the presence of large black ocelli (diameter 9-10 mm. on adult males, 2-3 mm. on hatchlings) in combination with only one dark marginal line. _T. s. spinifer_ resembles _asper_ in having ocelli or dots on the carapace but differs from _asper_ in having only one dark marginal line and larger ocelli. _T. s. spinifer_ differs from _hartwegi_ only in the large size of the ocelli. _T. s. spinifer_ resembles _hartwegi_ and _asper_ but differs from _pallidus_, _guadalupensis_ and _emoryi_ in having blackish spots and ocelli on the carapace and lacking whitish dots. _T. s. spinifer_ resembles _hartwegi_, _asper_, and _pallidus_ and differs from _guadalupensis_ and _emoryi_ in having conical or knoblike tubercles on the anterior edge of the carapace on large females.

_T. s. spinifer_ differs from the subspecies _asper_, _guadalupensis_ and _emoryi_ in having a relatively narrower head, and from _emoryi_ in having a relatively wider carapace. _T. s. spinifer_ resembles _hartwegi_ and _asper_ but differs from the other subspecies in having the carapace widest at a plane approximately one-half way back on the carapace. The subspecies _spinifer_ and _hartwegi_ have longer snouts than _pallidus_, _guadalupensis_, and _emoryi_. _T. s. spinifer_ differs from _asper_ but resembles all the other subspecies in having a relatively longer plastron.

_Remarks._--Lesueur's description of _Trionyx spiniferus_ (1827:258-261, Pl. 6) seems to be based mostly, if not entirely, on a large female (length of carapace, 13 inches), which was "Le plus grand des individus observes ..." (_op. cit._:258); an accompanying illustration depicting the dorsal surface of the bony carapace is unusual in lacking neurals (Pl. 6, E). Duméril and Bibron (1835:481) mentioned eight or nine additional specimens that Lesueur sent to the Museum of Natural History in Paris. Dr. Jean Guibé informed me under letter dated September 24, 1959, that a larger stuffed female, bearing catalog number 8808 is regarded as the holotype, and that there are seven additional specimens (1949, 4143, 8807, 8809-12) in the museum at Paris. All turtles were obtained by Lesueur from the Wabash River. To my knowledge no specimen that was available to Lesueur has been specifically designated as a type. Because the description seems to be based on one specimen, undoubtedly No. 8808, this specimen has been regarded as the holotype. However, Lesueur referred to several specimens and did not mention a type in the original description; consequently I prefer to regard No. 8808 as a lectotype.

Lesueur also described _Trionyx ocellatus_ (_op. cit._:261-263) as a variety of _T. spiniferus_ having ocelli, or parts thereof, on the carapace and mentioned three specimens. The total number of specimens that were available to Lesueur is unknown. One young alcoholic specimen having ocelli is in the British Museum (Natural History) (Gray, 1855:69). The same letter from Dr. Guibé stated that a specimen in the Museum of Natural History, Paris, No. 6957, having a carapace 17 centimeters in length, conforms to the characters of _ocellatus_ as mentioned by Lesueur, and was obtained from the Wabash River by Lesueur. Two of the specimens mentioned by Lesueur (_loc. cit._) are stated to be females. No. 6957 is an adult male and clearly shows the juvenal pattern; it is regarded as the lectotype of _T. ocellatus_ Lesueur, a name-combination, which is a synonym, based on a secondary sexual difference in pattern.

Rafinesque (1832:64) described a soft-shelled turtle from "the River Hudson between the falls of Hadley, Glen and Baker, and further up to the source" as _Apalone hudsonica_. The most outstanding characteristic was the presence of five claws on the digits of each limb. Rafinesque's recording of this characteristic was perhaps influenced by the illustration of a softshell in Bartram's _Travels_ that showed each limb with five, clawed digits. Perhaps this was the basis for Boulenger (1889:245, footnote) regarding _Apalone_ as "mythical." The large, yellowish, black-bordered spots, one behind and one in front of the eye presumably represent segments of the postocular stripe and the stripe on the snout; Rafinesque described the carapace as "entire ... the margin is yellowish unspotted, then comes a circular black line ..." and having "many round spots occulated and clouded by having a brown margin, with grey dots within." Except for five claws, the description is applicable to a softshell and referable to _T. s. spinifer_. To my knowledge, the only other records of the occurrence of soft-shelled turtles in the Hudson river drainage are those of Eights (_in_ Bishop, 1923:120, Mohawk River at Cohoes), and DeKay (1842:7, Mohawk River and Hudson River near Albany); presumably these records are the basis for the comments of Holbrook (_in_ Bishop, _loc. cit._), and symbolized as an isolated locality by Conant (1958:318, map 35). The type locality of _Apalone hudsonica_ is herein restricted to the Hudson River, near Baker's Falls, Saratoga County, New York.

Gray (1844:48) proposed the name _Tyrse argus_ for a specimen reported to have come from Sierra Leone, West Africa; later (1855:68), he referred the species to the genus _Trionyx_. After comparison with a specimen of _T. spiniferus_ Lesueur, Gray (1864:89) was "doubtful whether there must not have been some confusion about the habitat of the specimen [which formed the basis of the description of _Tyrse argus_], and whether it is not more probably a North American species." The same author (1869:222; 1870:109) listed _Tyrse argus_ as a synonym of _Callinia spinifera_ (= _Trionyx spiniferus_ Lesueur).

Agassiz (_op. cit._:406-07) described _Aspidonectes nuchalis_ on the basis of three adults from the Cumberland River and a number of young from the headwaters of the Tennessee River. Boulenger (1889:245, footnote 2) suggested that the status of _A. nuchalis_ required further investigation. The species was not generally recognized after the turn of the century. Barbour and Loveridge (1929:226) listed MCZ 1908 (one of the juveniles) and 1623-25 as cotypes. Stejneger (1944:52) showed that _nuchalis_ was not distinguishable from _T. s. spinifer_, and (_op. cit._:49) listed MCZ 1623-25 as cotypes. Schmidt (1953:110) restricted the type locality to the Cumberland River, near Nashville, Tennessee.

Agassiz (_loc. cit._) mentioned that _nuchalis_ "differs strikingly from Asp. spinifer in the much more elongated form of the male, and in the great development of the marginal spines and of the tubercles upon the carapace, ... But the most prominent specific character consists in the marked depressions on either side of the blunt median keel, and also in the triangular dilation of that keel behind the front margin of the carapace." These characters seem to be of no taxonomic worth. I have seen three syntypes (MCZ 1623-25) that undoubtedly correspond to the three adult specimens mentioned by Agassiz. All are females, measuring 19.5, 22.0, and 19.0 centimeters, respectively, in plastral length, and lack a contrasting mottled pattern on the carapace; the juvenal pattern is obscured, except for blackish spots at the edge of the carapace on MCZ 1625, and parts of an ocellus on MCZ 1624. The dorsal surfaces of the limbs are boldly marked. MCZ 1623, showing the diagnostic feature mentioned by Agassiz, is photographed by Stejneger (_op. cit._:Pls. 14, 15), and may be regarded as the lectotype of _Aspidonectes nuchalis_ Agassiz. MCZ 1908 is one of the young syntypes mentioned by Agassiz, and is referable to _spinifer_. The juvenal pattern consists of spots and ocelli; the plastron measures 3.1 centimeters in length, and the carapace 4.2 centimeters.

Wied-Neuwied (1865:55-57, Pl. 5) described the species _?G_[_ymnopus_] _olivaceus_, but was uncertain whether his interpretation was based on a species, a variety or a secondary sexual difference. Wied-Neuwied mentioned that Lesueur had already named this soft-shelled turtle as _Trionyx ocellatus_, and agreed with Lesueur that those turtles having occulated spots on the carapace were distinguishable from _T. spiniferus_ and _T. muticus_. But because Duméril and Bibron in their _Erpétologie Général_ failed to recognize _T. ocellatus_, Wied-Neuwied felt obliged to bring it to the attention of his American colleagues and he renamed it. Wied-Neuwied also stated, in the context of a synonym, "Beschreibung einer Reise in Nord-America Bd. I., pag. 140." This comment presumably refers to his earlier description of _T. annulifer_ (1838:140); seemingly Wied-Neuwied considered _T. annulifer_ and _G. olivacea_ as conspecific, although there is no mention of _annulifer_ in the text proper. Stejneger (_op. cit._:49) designated the type locality of _T. annulifer_ as the Ohio River at Pittsburgh, Pennsylvania, and of _Gymnopus olivacea_ as New Harmony, Wabash River, Illinois (_lapsus_ for Indiana).

_Trionyx spiniferus_ was questionably considered distinct from _T. ferox_ by Lesueur who listed "Testudo ferox Gm. Tortue de Pennant?" and "Trionyx georgicus Geoffr.?" as synonyms. Subsequently, most authors considered _T. spiniferus_ synonymous with _T. ferox_ until Agassiz (1857) pointed out differences between the two species.

The average size of the ocelli on the carapace of the subspecies _spinifer_ decreases westward toward the Mississippi River; ocelli of different sizes occur on different individuals from the same state and presumably from the same population. For example, INHS 2281, plastron 9.9 centimeters in length, from Effingham County, Illinois, has some ocelli eight millimeters in diameter, whereas a larger male from the same locality, UI 1322, plastron 11.6 centimeters in length, has the largest ocelli only five millimeters in diameter. For convenience, all softshells having locality data from states east of the Mississippi River are referred to _spinifer_, recognizing that intergradation occurs with _hartwegi_ over a broad area paralleling the Mississippi River. The type locality of _spinifer_ is in an area where most turtles do not have the larger ocelli (diameter of seven to ten mm. on adult males); however, some individuals from the Wabash River (UMMZ 63523, adult male, plastron 11.5 cm. in length, ocelli diameter seven mm.) agree with more "typical" _spinifer_ to the east. Intergradation with _asper_ possibly occurs in that part of the Tennessee River in eastern Tennessee as exemplified by UMMZ 59198.

Published reports indicate that _T. s. spinifer_ is not abundant in some of the northeasterly parts of its geographic range. Adams and Clark (1958:10) wrote that few softshells at Long Point on the Canadian side of Lake Erie are "ever collected and the area's game keepers report ... (none) ... seen in recent years. They also tell of recurrent severe stormy winters in which the muddy bottom of the marshland was repeatedly churned up and frozen. Such climatic conditions could easily destroy a large part of the _Trionyx_ population overwintering in the mud bottom." Wright (1919:8) reported that softshells are "rarely seen" in bays on the New York side of Lake Ontario, and Babcock (1938:53) wrote that _spinifer_ "is not common in Lake Champlain."

_T. s. spinifer_ probably extended its geographic range into the Hudson River drainage of New York _via_ the Erie Canal (connected Buffalo and Albany) after its completion in the early 1800's (DeKay, 1842:7). Now, the New York Barge Canal (essentially the Erie Canal, but with minor changes in course and the addition of several spurs) provides an avenue for dispersal of _spinifer_ to the Hudson River drainage, Lake Ontario and intervening waterways in New York (Mertens, 1928:199). Netting (1944:86-87), however, suggested that _spinifer_ occupied Lake Champlain, the Finger Lakes, Mohawk River and upper Hudson in the late stages of the formation of the Great Lakes.

A publication not seen by me is that of Mansueti and Wallace (1960). Its title suggests that _Trionyx_ occurs in Maryland.

The unsuccessful introduction of _T. s. spinifer_ in the Delaware drainage in New Jersey has been discussed by Fowler (1907:213), who wrote that they were found as early as the late 1860's and were introduced when young presumably to stock aquaria. Records of occurrence include Cooper's Creek, Camden County (Stone, 1906:168); Woodbury, Gloucester County (Cope, 1894:889); and Paulins Kill at Hainesburg, Warren County (Johnson, 1894:889).

Surface (1908:122) believed that soft-shelled turtles "have doubtless been introduced into the eastern part of Pennsylvania through the canal from the Western and Central part of New York," and Roddy (_in_ Neill, 1951:21) suggested that the species may be found in the Susquehanna River. Babcock (1919:420) mentioned a young specimen of _spinifer_ in the collection of the Boston Society of Natural History that was obtained "in White River, Vermont," a tributary of the Connecticut River of the Atlantic Coast drainage; seemingly this record has not been accepted and the species is not established. To my knowledge, populations of _T. s. spinifer_ do not occur in rivers of the Atlantic Coast drainage, except probably the Hudson-Mohawk drainage.

Stockwell (1878:401) wrote that _spinifer_ was found "as high as Athabasca." Presumably Stockwell referred to Lake Athabaska in northern Alberta and Saskatchewan, Canada, a region where soft-shelled turtles are unknown; see also the comments by Stejneger (1944:52).

_Specimens examined._--Total 250 as follows: ALABAMA: _Morgan_: UMMZ 99578, "near" Decatur.

ILLINOIS: _Adams_: INHS 2150, Quincy. _Bond_: INHS 8345, Greenville. _Carroll_: CNHM 42116, Ordnance School Proving Ground. _Cass_: INHS 2151, Beardstown. _Champaign_: INHS 2273, 2311, 2413, 3142, "near" Seymour; INHS 4229, Champaign; INHS 6163, Sidney. _Christian_: INHS 1560, Pana. _Coles_: INHS 1968-69, 2 mi. W Charleston. _Cumberland_: INHS 2282, Greenup. _De Witt_: INHS 7674, Farmer City. _Effingham_: UI 1322, 2281, 19365, "near" Effingham. _Fulton_: INHS 5531, 2 mi. NE Bluff City, Schyler County; UI 23449, Liverpool; UI 24611, Spoon River, 18 mi. NW Canton. _Hancock_: USNM 53522, 59277, "near" Hamilton. _Iroquois_: INHS 6869-70, 2.5 mi. N Crescent City. _Jackson_: TU 1369 (12), Elkville. _Kane_: CNHM 42400, Aurora. _Kankakee_: CNHM 324, Momence. _Kendall_: UI 2411, Plano. _Logan_: INHS 7171-72, 6 mi. N Lincoln. _Madison_: USNM 60571. _Macoupin_: UI 2401-02, Beaver Dam Lake. _Mason_: CNHM 346, 470, INHS 1122, 1559, 5756-58, UI 42, 2404, Havana, Lake Chautauqua. _Mercer_: CNHM 3220, New Boston. _Morgan_: CNHM 2067 (2), 3290, 3303-04, 3306, INHS 2152, 2154, 5132-37, USNM 54747, Meredosia. _Moultrie_: INHS 8989, 2 mi. NW Lovington. _Peoria_: UI 2406-10, Peoria. _Pope_: INHS 5505, Lake Glendale. _Putnam_: UMMZ 81604-14, 5 mi. N Henry, Marshall County. _Schuyler_: UI 2405, "near" Ripley, Brown County. _Scott_: INHS 2149, 2153, Naples. _Union_: CNHM 18623, 6 mi. SW Jonesboro. _Vermilion_: INHS 3142, Muncie; INHS (1 untagged); UI 1970, 3209, Danville; UI 2403, 1.5 mi. E Oakwood; UI 16265, Kickapoo State Park. _Wabash_: USNM 12061, Mt. Carmel. _Winnebago_: INHS 7185, Kishwaukee Forest Preserve; INHS 7294, 1/2 mi. S Shirland. _County unknown_: USNM 7661.

INDIANA: _Bartholomew_: UMMZ 61060, 10 mi. W Columbus. _Carroll_: USNM 42905-06, Burlington. _Clark_: UMMZ 110599, 14-mile Creek, 3 mi. NW Charleston. _Decatur_: UMMZ 55416, 3 mi. S Westport. _Elkhart_: UMMZ 105598, Elkhart River, south of Goshen. _Gibson_: UMMZ 89744, Foot's Pond. _Johnson_: UMMZ 108062, 2 mi. S Trafalgar. _Knox_: USNM 22711, Vincennes. _Kosciusko_: AMNH 8379, UMMZ 84287 (5), Winona Lake; UMMZ 110235, Wawasee Lake. _Lake_: CNHM 11019, 11021-24, Crown Point. _Marion_: UMMZ 103393, Ravenswood; UMMZ 110236, 1 mi. N Lawrence. _Marshall_: CNHM 39299; USNM 33495, Yellow River north of Burr Oak; USNM 33496-501, 35404, 42583-84, Lake Maxinkuckee. _Wells_: UMMZ 63523, Wabash River, Bluffton. _County unknown_ (Lagrange or Marshall): USNM 50670, Twin Lakes.

KENTUCKY: _Casey_: UMMZ 112252, trib. of Green River, south of Yosemite. _Green_: UMMZ 116718, Little Barren River, 1.5 mi. E Monroe, Hart County. _Rockcastle_: UMMZ 98767, Rockcastle River, 5 mi. above Livingston.

MICHIGAN: _Allegan_: UMMZ 42112, Kalamazoo River. _Barry_: UMMZ 53874, Thornapple River, 3 mi. NW Hastings. _Bay_: UMMZ 74670. _Branch_: UMMZ 95615, 1 mi. S Kinderhook; UMMZ 70748, Hog Creek. _Calhoun_: UMMZ 89950 (3); UMMZ 79133, near Battle Creek. _Cass_: UMMZ 40866-67, 53005, Diamond Lake; UMMZ 40868, 52948, Long Lake. _Jackson_: UMMZ 72494. _Kalamazoo_: UMMZ 42130, 80534, Kalamazoo; UMMZ 90506, Gull Lake; UMMZ 92599, Kellogg Bird Sanctuary. _Lenawee_: UMMZ 72457, Devil's Lake; UMMZ 74662, Wolf Lake Park. _Livingston_: UMMZ 54401, 76190, Portage Lake. _Monroe_: UMMZ 44604-06, USNM 51213, "near" Monroe. _Newaygo_: UMMZ 63469. _Oakland_: UMMZ 64363, Hay's Creek; UMMZ 96539, Clinton River. _Ottawa_: UMMZ 81699. _St. Joseph_: UMMZ 38876, 38889, "near" White Pigeon; UMMZ 96537, Corey Lake. _Van Buren_: UMMZ 90003, Wolf River, west of Kalamazoo, Kalamazoo County. _Washtenaw_: SM 2035, 2038, 2105, UMMZ 39847, 96538, "near" Ann Arbor; UMMZ 35765, 35769, 74518 (2), Portage Lake; UMMZ 54402-03, Little Lake; UMMZ 89659, Huron River, Dexter; UMMZ 110583-85. _County unknown_ (Washtenaw or Livingston): UMMZ 54400, Huron River near Portage Lake.

MISSISSIPPI: _Adams_: MCZ 46615, UMMZ 76446, "near" Natchez; MCZ 46621, 46633, USNM 01084, 01086, Washington. _Coahoma_: AMNH 5289, 5285-86, Moon Lake. _Lafayette_: MCZ 37173, Oxford; USNM 7650, Abbeville? (reported from Abbeville, South Carolina by Pickens, 1927:113; see discussion by Stejneger, 1944:50, and my comments on page 509 beyond). _LeFlore_: USNM 73668-69, Greenwood. _Madison_: USNM 95192, Big Black River. _Washington_: USNM 115980, Deer Creek. _Yazoo_: UMMZ 86669, Panther Creek west of Yazoo City; UMMZ 83304, Yazoo City.

NEW YORK: _Monroe_: CNHM 92001-02, Genesee River, Rochester. _Wayne_: AMNH 69931, CNHM 92004, Sodus Bay.

OHIO: _Athens_: UMMZ 111793, east branch Shade Creek. _Franklin_: USNM 26290. _Lucas_: USNM 51214, Toledo. _Pike_: UMMZ 99309, Morgan's Fork, Sunfish Creek. _Warren_: AMNH 4763, Little Miami River, 3 mi. below Morrow. _County unknown_: USNM 21128-29, Cuyahoga River.

TENNESSEE: _Benton_: UMMZ 113036, Eagle Creek, 1/2 mi. E Holliday. _Bradley_: UMMZ 59197, west branch of Chestnee Creek, 7 mi. E Cleveland. _Claiborne_: USNM 86677, 5 mi. SE Cumberland Gap, Powell River. _Davidson_: MCZ 1623-25, Cumberland River near Nashville (restricted locality); USNM 7165-67, Nashville. _Decatur_: KU 3000, Perryville. _Hamilton_: USNM 131861, Chattanooga. _Monroe_: TU 16058, Little Tennessee River, 10 mi. N Madisonville. _Obion_: UMMZ 53199, USNM 102911, Reelfoot Lake. _Overton_: UMMZ 69561 (2), Wirmingham. _Sevier_: TU 16132, UMMZ 86735, USNM 86681-82, near Sevierville; UMMZ 86734, Walden Creek "near" Gatlinburg. _County unknown_: MCZ 1908, headwaters of Tennessee River.

VIRGINIA: _Smythe_: USNM 101386, Holston River, Seven Mile Ford.

WEST VIRGINIA: _McDowell_: USNM 33767, Dry Fork, Perryville (county questionable, perhaps Randolph County).

WISCONSIN: _Chippewa_: CNHM 8223, Lake Wissota, mouth of Yellow River, Anson Twp. _Polk_: UMMZ 72511-12, St. Croix River "near" Never's Dam. _County unknown_: CNHM 15971, Eau Claire River.

_Records in the literature._--ONTARIO: _Carleton_: Ottawa (questionable record). _Essex_: Point Pelee. _Haldimand_: Dunville. _Kent_: Lake St. Clair. _Norfolk_: Long Point. _Oxford_: Beachville. _Wentworth_: Hamilton Bay (Logier and Toner, 1955:51).

QUEBEC: _Iberville_: Richelieu River at Iberville (Logier and Toner, 1955:51).

ALABAMA: _Lawrence_: Courtland (Stejneger, 1944:53).

ILLINOIS: _Boone_: Belvidere. _Bureau_: Bureau. _Cass_: Chandlerville. _Clay_: Louisville (Cahn, 1937:189). _Cook_: Lake Michigan (Kennicott _in_ Stejneger, 1944:44); Evanston (Necker, 1939:10); Chicago (Schmidt and Necker, 1935:76). _Crawford_: Robinson. _Douglas_: northern part of county (P. W. Smith, 1947:39). _Fayette_: Vandalia. _Fulton_: Ellisville (Cahn, _loc. cit._). _Grundy_: Morris (Stille and Edgren, 1948:201). _Jackson_: Jacob (Cagle, 1942:158). _Jersey_: Grafton (Cahn, _loc. cit._). _Kane_: Batavia; Dundee Game Farm (Stille and Edgren, _loc. cit._). _Kankakee_: Kankakee River near Altort (Necker, _loc. cit._). _Lake_: Fox Lake. _LaSalle_: Streator (Cahn, _loc. cit._). _Lawrence_: (Hahn _in_ Stejneger, 1944:44). _Lee_: symbol on map (Cahn, _loc. cit._). _McHenry_: McHenry (Stille and Edgren, _loc. cit._). _Macon_: Decatur. _Macoupin_: Carlinville (Cahn, _loc. cit._). _Ogle_: Oregon (Garman _in_ Cahn, _loc. cit._). _Randolph_: Chester, Reily Lake. _Rock Island_: Barstow, Hillsdale, Rock Island (Cahn, _loc. cit._). _Saline_: Horseshoe Lake (Stein, 1954:312). _Stephenson_: Freeport (Cahn, _loc. cit._). _Union_: Bluff Lake (Garman _in_ Cahn, _loc. cit._). _Whiteside_: Sterling, symbol on map (Cahn, _loc. cit._). _Williamson_: Marion (Cagle, 1942:158). _Winnebago_: Rockton; symbol in western part of county (Cahn, _loc. cit._). _County unknown_: Fox River (Yarrow, 1882:29).

INDIANA: _Brown_: 1 mi. below Helmsburg (Myers, 1927:339). _Clay_: Eel River (Kirsch _in_ Stejneger, 1944:45). _Franklin_: (Hughes _in_ Stejneger, _loc. cit._). _Jasper_: Jasper-Pulaski Game Preserve (Swanson, 1939:690). _Jefferson_: Madison (Myers, _loc. cit._). _Marion_: Irvington (Stejneger, _op. cit._:55). _Marshall_: 2 mi. NW Culver (KKA). _Monroe_: Bloomington (McLain _in_ Stejneger, _op. cit._:45). _Newton_: Lake Village (Stille and Edgren, _loc. cit._). _Posey_: Wabash River at New Harmony (Lesueur, 1827:257). _Starke_: Grant (Stille and Edgren, _loc. cit._). _Steuben_: Fish Creek "near" Hamilton (Stejneger, _op. cit._:53). _County unknown_ (Knox or Starke): USNM 72387, Knox (Stejneger, _op. cit._:55); "White Water valley," east-central part of state (Butler, 1894:224). USNM 8359 (= _Trionyx spinifer asper_) has been erroneously recorded from Madison, Indiana, by Yarrow (1882:29) and Hay (1892:145); see discussion by Cahn (1937:200) and Stejneger, (_op. cit._:73, 75).

KENTUCKY: _Edmonson_: Green River, Mammoth Cave National Park (Hibbard, 1936:281). _Fleming_: Fox Creek (Welter and Carr, 1939:130). _Jefferson_: (Funkhouser, 1925:71). _Morgan_: (Stejneger, 1944:54). _County unknown_: Ohio and Pond rivers (Funkhouser, _loc. cit._).

MICHIGAN: _Berrien_: mouth of St. Joseph River at St. Joseph (Lagler, 1943:303). _Eaton_: Brookfield; Olivet (Clark _in_ Ruthven, Thompson and Thompson, 1912:133). _Genesee_: (Miles _in_ Ruthven, Thompson and Thompson, _loc. cit._). _Iosco_: (Lagler, 1943:283, symbol on map). _Kent_: (Lagler, _loc. cit._). _Montcalm_: (Clark _in_ Ruthven, Thompson and Thompson, _loc. cit._). _Muskegon_: Muskegon River "near" Muskegon (Lagler, _op. cit._:303). _Van Buren_: Reynolds Lake, 2.5 mi. E Lawrence (Edgren, 1942:180).

MISSISSIPPI: _De Soto_: Lake Cormorant (Stejneger, 1944:55). _Holmes_: Thornton (Cook, 1946:185). _Humphreys_: Belzoni (Stejneger, _loc. cit._). _Sunflower_: _Warren_: Vicksburg, Eagle Lake (Cook, _loc. cit._). _Washington_: Lake Washington (Smith and List, 1955:125); Greenville (Stejneger, _loc. cit._).

NEW YORK: _Albany_: Hudson River at Albany (DeKay, 1842:7); Mohawk River at Cohoes (Eights _in_ Bishop, 1923:120). _Cattaraugus_: Allegheny River and Red House Lake in Allegheny State Park (Eaton, 1945:115). _Chautauqua_: Lake Chautauqua (DeKay, _loc. cit._). _Monroe_: Braddocks Bay and Long Pond on Lake Ontario (Wright, 1919:8). _Saratoga_: Hudson River near Baker's Falls (restricted locality, Rafinesque, 1832:64). _County unknown_: Lake Cayuga; Mohawk River (DeKay, _loc. cit._).

OHIO (Conant, 1951:158-59, 264, except records from Allen, Geauga and Noble counties): _Allen_: Sugar Creek, 6 mi. N Lima (Adler and Dennis, 1960:27). _Ashland_: Long Lake, Lake Twp.; Black Fork, Sec. 27, Green Twp. _Athens_: Hocking River "near" Athens; "near" Fisher, Alexander Twp. _Auglaize_: Pusheta Creek, west of Wapakoneta. _Brown_: White Oak Creek, 1 mi. N Higginsport. _Butler_: Oxford. _Champaign_: Mad River, 4 mi. SW Urbana. _Coshocton_: Walhouding River, below dam. _Defiance_: Auglaize River, Shawnee Scout Camp, Defiance Twp. _Erie_: Huron; Sandusky. _Fairfield_: Buckeye Lake. _Franklin_: Alum Creek, Westerville; Columbus. _Geauga_: Chardon Twp. (Wood, 1959:8). _Greene_: Huffman Dam. _Hamilton_: Harrison; mouth of Miami River. _Hardin_: "near" Hepburn. _Henry_: Maumee River, east of Napoleon; Maumee River "near" Texas; Maumee River, 3 mi. W Texas. _Highland_: Little Brush Creek, 2 mi. N Sinking Spring. _Huron_: Huron River "near" Monroeville. _Jackson_: Canter's Cove, Jackson Twp.; Jackson Lake. _Knox_: Brinkhaven. _Lake_: east branch Chagrin River, Kirtland; Grand River, 4 mi. E Painesville. _Lawrence_: Pine Creek, Elizabeth Twp. _Logan_: Miami River, "near" Indian Lake. _Lorain_: Oberlin. _Lucas_: Lake Erie at Reno Beach, Jerusalem Twp.; Lake Erie, 1/2 mi. offshore from mouth of Crane Creek; Maumee River at Maumee; Swan Creek, W of Toledo; "near" Waterville; Swan Creek "near" Whitehorse. _Madison_: London. _Medina_: Hinckley Lake. _Meigs_: Shade River, below Darwin. _Miami_: Miami River, above Troy. _Monroe_: Cranenest Fork, Green Twp. _Montgomery_: Mad River, Dayton; Miami River, Dayton; Stillwater River, Dayton. _Morrow_: Kokosing River, Franklin Twp. _Noble_: Jct. Sharon Twp. 1 and St. Rt. 78. (Adler and Dennis, 1960:27). _Ottawa_: East Harbour, Catawba Island. _Pike_: Chenoweth Fork, Sunfish Twp.; Scioto River, Camp Creek Twp. _Ross_: Paint Creek near Bainbridge. _Vinton_: Lake Hope; Lake Alma. _Warren_: Fort Ancient. _Washington_: Dam No. 2, Muskingum River, "near" Marietta. _Williams_: 1 mi. S Blakesley; St. Joseph River "near" Blakesley; West Branch, St. Joseph River, Sec. 8, Bridgewater Twp.; Edgerton. _Wood_: Grand Rapids; Grassy Creek, Rossford; Haskins; Maumee River opposite Toledo.

PENNSYLVANIA: _Allegheny_: Monongahela River above McKeesport (Atkinson, 1901:154); Ohio River at Pittsburgh (Wied-Neuwied _in_ Stejneger, 1944:44, 49). _Armstrong_: (Swanson, 1952:165). _Clarion_: Clarion River "near" Clarion (Allen, 1955:228); Foxburg (= Foxbury?, Boulenger, 1889:260). _Crawford_: _Elk_: _Erie_: Edinboro Lake. _Forest_: (Swanson, _loc. cit._). _Indiana_: Plum Creek; Crooked Creek (Netting _in_ Stejneger, 1944:48). _McKean_: (Swanson, _loc. cit._). _Somerset_: Stoyestown (Surface, 1908:122). _Warren_: _Venango_: Allegheny River south of Franklin (Swanson, _loc. cit._).

TENNESSEE: _Chester_: South Fork, Forked Deer River just E Henderson (Endsley, 1954:40). _Clay_: Mill Creek, 3 mi. from Butler's Landing; Obey River above mouth of Wolf River at Lilydale; mouth of Wolf River (Shoup, Peyton and Gentry, 1941:75); Iron Creek "near" Willow Grove (Stejneger, 1944:56). _Fentress_: _Jackson_: (Gentry, 1941:332). _Lake_: Reelfoot Lake (Parker, 1948:29). _Obion_: Walnut Log (Parker, 1937:85); east shore of Reelfoot Lake, Samburg (Rhoads, 1895:386). _Overton_: Medlock Branch, tributary of West Fork Obey River north of Allred (Shoup, Peyton and Gentry, _loc. cit._). _Roane_: 2 mi. S Kingston (Stejneger, 1944:55).

VERMONT: _Chittenden_: Lake Champlain, mouth of Winooski River; "near" Burlington; Milton (= Minton) (Babcock, 1919:420). _Franklin_: Swanton (Stejneger, 1944:55).

WEST VIRGINIA: _Randolph_: Tygart River at Elkins (Green, 1937:116).

WISCONSIN: _Burnett_: _Crawford_: (Pope and Dickinson, 1928:83). _Dane_: Lake Wingra, Madison (Noland, 1951:54). _Grant_: (Pope and Dickinson, _loc. cit._). _Green Lake_: Berlin (AMNH 6840-41, listed in card file March 2, 1959). _Jefferson_: Lake Mills (Dickinson, 1950:75). _La Crosse_: West Salem (Pope, 1930:281). _Oneida_: _Pepin_: (Pope and Dickinson, _loc. cit._). _Racine_: Eagle Lake (Edgren, 1944:498); Burlington; Rochester (Stille and Edgren, 1948:201). _Sheboygan_: Sheboygan (KKA). _Trempealeau_: _Vernon_: "near" Viroqua (Pope, _loc. cit._). _Walworth_: Lake Beulah (Dickinson, _loc. cit._). _Washburn_: (Pope and Dickinson, _loc. cit._). _Waukesha_: Lac La Belle (Cahn, 1929:8). _Winnebago_: Wolfe River (Dickinson, _loc. cit._).

=Trionyx spinifer hartwegi= (Conant and Goin)

Western Spiny Softshell

Plates 35 and 36

_Amyda spinifera hartwegi_ Conant and Goin, Occas. Papers Mus. Zool. Univ. Mich., No. 510:1, pl. 1, map 1, June 15, 1948.

_T[rionyx] s[pinifer] hartwegi_ Schwartz, Charleston Mus. Leaflet, No. 26:11, May, 1956.

_Type._--Holotype, UMMZ 95365; alcoholic adult male; obtained at Wichita, Sedgwick County, Kansas, in May, 1945, by Robert Young.

_Range._--Central United States in tributaries flowing into the Mississippi River from the west, except the Red River drainage; eastern Montana, North Dakota, and southern Minnesota south to eastern Colorado, northern Oklahoma and Arkansas (see map, Fig. 19).

_Diagnosis._--Juvenal pattern of small ocelli, rarely as large as two millimeters in diameter, or usually solid black dots that are not much larger in center of carapace than at sides (mean OD/PL, Kansas, .022); only one dark marginal line separating pale rim of carapace from dorsal ground color.

_Description._--Plastral length of smallest hatchling, 2.8 centimeters (USNM 9928); of largest male, 13.1 centimeters (USNM 55687); of largest female, 25.5 centimeters (KU 2283).

Carapace olive, having small ocelli or black spots that are not much larger in the center of the carapace than at the sides; pale rim of carapace separated from darker ground color by one dark marginal line and not four or five times wider posteriorly than laterally; large females often having black dots at sides of carapace on mottled and blotched pattern; pattern on snout of pale, dark-bordered stripes that unite forming acute angle in front of eyes; well-defined dark markings in subocular and postlabial region; pattern contrasting with ground color on side of head; postlabial stripe broken, interrupted; pale postocular stripe having blackish borders interrupted, not joining with postlabial stripes; dorsal surface of soft parts of body having contrasting pattern, largest blackish marks on hind limbs; elongate tail of males having pale dorsolateral bands with well-defined, lower, blackish borders; patterns on soft parts of body usually obscured or absent on large females; underparts whitish, often having blackish marks, except in center of plastral area; dark marks on webbing of limbs, palms and soles; dark streaks often coincident with digits; tubercles along anterior edge of carapace small and conical on adult males, and conical or knoblike on large females; accessory, knoblike tubercles in nuchal region and in middle of carapace posteriorly on large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 7.0 centimeters or less, 4.24, and exceeding 7.0 centimeters, 5.33; ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.5 centimeters or less, 1.12, and exceeding 8.5 centimeters, 1.19; mean CL/PCW, 2.00; mean SL/HW, 1.30 (including subspecies _spinifer_); mean CL/PL, 1.38.

_Variation._--Variants include: CNHM 8949, UMMZ 72511 and TU 14591 having ocelli approximately 4 millimeters in diameter that are almost solid spots; KU 17728 having pale stripes on snout that lack black, inner borders; TTC 719 (female, plastral length 20.7 cm.), having distinct pattern on snout; USNM 14535, 17823, 55684, and 123446 (from different localities) having markings confined to margins of carapace (Stejneger, 1944:66, suggested that USNM 17823 probably came from Texas); UMMZ 92667 (female, plastral length 6.7 cm.) lacking pattern on carapace.

_Comparisons._--_T. s. hartwegi_ can be distinguished from all other subspecies of _T. spinifer_ by the presence of small dots and ocelli on the carapace that are all of approximately the same size in combination with only one dark marginal line. _T. s. hartwegi_ resembles _asper_ in having small blackish ocelli or dots on the carapace but differs from _asper_ in having only one dark marginal line. _T. s. hartwegi_ differs from _spinifer_ only in the small size of the ocelli. _T. s. hartwegi_ resembles _spinifer_ and _asper_, but differs from _pallidus_, _guadalupensis_ and _emoryi_ in having blackish spots and ocelli on the carapace and lacking small whitish spots. _T. s. hartwegi_ resembles _spinifer_, _asper_ and _pallidus_ but differs from _guadalupensis_ and _emoryi_ in having conical or knoblike tubercles on the anterior edge of the carapace on large females.

_T. s. hartwegi_ differs from the subspecies _asper_, _guadalupensis_ and _emoryi_ in having a narrower head, and from _emoryi_ in having a wider carapace. _T. s. hartwegi_ resembles _spinifer_ and _asper_ but differs from the other subspecies in having the carapace widest at a plane approximately one-half way back on the carapace. _T. s. hartwegi_ and _spinifer_ have longer snouts than do _pallidus_ and _guadalupensis_ or _emoryi_. _T. s. hartwegi_ differs from _asper_ but resembles the other subspecies in having a relatively longer plastron.

_Remarks._--The validity of _T. s. hartwegi_ has never been questioned. It intergrades with _spinifer_ over a broad area paralleling the Mississippi River. For convenience, specimens occurring west of the Mississippi River are referred to the subspecies _hartwegi_. Figure 8 shows much variation in size of ocelli on different individuals from the same state. For example, UMMZ 92667, plastral length 6.7 centimeters has a uniform pale brown carapace lacking any dark marks, whereas UMMZ 92652, plastral length 5.9 centimeters has some ocelli three millimeters in diameter on the carapace. Both are from Iowa. One specimen from Kansas, KU 1954 (Doniphan County, plastral length 11.8 cm.), has ocelli four millimeters in diameter, and USNM 7648 captured farther west at Fort Laramie, Wyoming, an adult male having a plastral length of 11.0 centimeters, has some ocelli five millimeters in diameter on the carapace. TTC 1090, an adult male from the panhandle of Texas has some ocelli so much as 5.5 millimeters in diameter. The size of the ocelli seemingly varies in the same local population.

Specimens of _T. spinifer_ in the lower Mississippi Valley are intergrades. Most individuals have small black dots on the carapace; some have small ocelli (TU 7216, 7501, 11912, 12123-24) interspersed with black dots (TU 5863), others have black dots confined to the edge of the carapace (TU 157, 4539, 7105), and still others have no pattern on the carapace (TU 7506, 13698.1, 10087.6). Two large males (TU 11580, 13025) have large ocelli (approximately five mm. in diameter) that have nearly black centers. In general, there is more dark pigmentation than farther north; some specimens have extensive pigmentation on the ventral surface of the carapace and soft parts of the body (TU 156, 5648). The dorsal surface of the limbs, especially the hind limbs, have a bold, black marbling and may be almost completely black (TU 5484, 5597). Many females, not exceeding plastral lengths of 7.0 centimeters, have a pale blotched pattern of lichenlike figures or have ill-defined black dots on the carapace (TU 10087, 13698.13, 13753.15).

Localities of specimens of _T. spinifer_ occurring in the Mississippi River drainage in Mississippi are arbitrarily listed under the account of the subspecies _spinifer_, whereas those in Louisiana (excluding _pallidus_) are listed under the account of _hartwegi_.

Neither Over (1943) nor Wheeler (1947:169) record _T. s. hartwegi_, respectively, from South Dakota or North Dakota; records from the Missouri River drainage in Montana suggest the occurrence of the species in that drainage in North and South Dakota.

_Specimens examined._--Total, 392 as follows: ARKANSAS: _Clay_: UMMZ 70735 (2), 7 mi. S St. Francis. _Crawford_: USNM 95352, Lee Creek, 7 mi. NW Natural Dam. _Drew_: CNHM 40785. _Lafayette_: KU 2225-29, 2944 (one of three specimens bearing last catalog number), 2963 (one of three specimens bearing this catalog number), 2964 (one of two specimens bearing this catalog number), Lewisville (see remarks under the account of the subspecies _pallidus_). _Lawrence_: CNHM 8949; CNHM 12598-600, 12602-04, TU 5855, UI 2413, Imboden; UI 2412, Black River at Powhatan. _Marion_: TU 14591 (6), White River at Cotter. _Prairie_: KU 1867, 1869, 1879, 1949-51, 2280-83, 2285-91 (2 specimens bear catalog number 2287), 2307, 2761-62, 2666, 2826, 2842, 3346-47, White River at DeValls Bluff. _Pulaski_: UMMZ 96540, Little Rock. _Saline_: USNM 17823, Saline River at Benton. _Searcy_: UMMZ 92755, Little Red River, 1.5 mi. SE Leslie. _Yell_: TU 14565, Petit Jean Creek, 10 mi. N Casa. _County unknown_: CNHM 28566-67, Ouachita River.

IOWA: _Allamakee_: UMMZ 72556-58, 92642-49, Mississippi River "near" Lansing. _Appanoose_: UMMZ 92667, Chariton River, 4.3 mi. N. Centerville. _Decatur_: UMMZ 92651, Grand River, 3.5 mi. WSW Decatur. _Dickinson_: UMMZ 55249, Milford; UMMZ 92655, Spirit Lake Twp. _Hamilton_: USNM 9928, Webster City. _Hardin_: UMMZ 92650, Eldora. _Louisa_: UMMZ 92654, Muscatine Slough, 12 mi. SW Muscatine, Muscatine County. _Muscatine_: INHS 7675, 5.5 mi. SE Muscatine; USNM 54730-32, Fairport. _Scott_: CNHM 433, Davenport; UMMZ 92656, Steamboat Slough, 2 mi. N Princeton. _Story_: UMMZ 92653, Squaw Creek at Ames. _Washington_: UMMZ 92652, English River, 2 mi. E Riverside.

KANSAS: _Anderson_: KU 52286-87, 3-1/4 mi. E, 1/2 mi. N Colony. _Atchison_: UMMZ 66939-41, Atchison. _Barber_: KU 17728, 4.5 mi. S Sun City; KU 41379, 41742, 6 mi. N, 3.5 mi. E Sharon; USNM 100580, Medicine River, 1 mi. S Lake City. _Cherokee_: KU 1323, Galena. _Comanche_: KU 18385, 3-4 mi. SE Arrington. _Cowley_: UMMZ 75963, USNM 90441-44, 91022, 100529-30, "near" Winfield. _Doniphan_: KU 1943, 1952-54, Doniphan Lake. _Douglas_: KU 1955-56, Wakarusa River; KU 40176-77, Kansas River at Lawrence. _Franklin_: KU 3290. _Hamilton_: KU 2990, Syracuse. _Harper_: KU 18159, 1 mi. N Harper. _Kingman_: USNM 95261, 2 mi. E Calista. _Labette_: KU 3339. _Lane_: KU 3738-41, Pendennis. _Logan_: KU 16531, Smoky Hill River, 3 mi. SW Elkader. _Meade_: KU 40210, Crooked Creek, 12.5 mi. S, 1-1/4 mi. W Meade. _Montgomery_: KU 3731-32, Independence; KU 50856, Cherryvale Lake. _Neosho_: UMMZ 69294, Caneville Creek, 32 mi. N. Parsons, Labette County. _Osage_: KU 3294-96, Appanoose Creek. _Pratt_: KU 15931-32, 15934, State Fish Hatchery "near" Pratt. _Riley_: KU 48239, McDowell Creek, WSW Manhattan; UMMZ 64434, "near" Manhattan. _Russell_: KU 3289. _Sedgwick_: UMMZ 95363-65, Wichita. _Shawnee_: USNM 123446, Kansas River at Topeka. _Stafford_: KU 3758, Little Salt Marsh; KU 41743, 13.5 mi. N, 6 mi. E Stafford. _Trego_: KU 2757, 3769, Smoky Hill River, 10 mi. N (NNE) Utica, Ness County; KU 51517, Saline River, 5 mi. N, 1/2 mi. E Wakeeney. _Wilson_: KU 56744-45, Verdigris River, 1 mi. S Altoona. _Woodson_: KU 55295, Neosho River, 1/2 mi. E, 1-1/2 mi. S Neosho Falls. _County unknown_: USNM 51529.

LOUISIANA: _Catahoula_: TU 12629, Ouachita River, 4 mi. N Harrisonburg. _Claiborne_: TU 13080, Caney Lake "near" Summerfield. _Concordia_: KU 50849, Tensas River at Clayton; TU 16524 (3), USNM 012349, Lake Concordia; USNM 99865, Red River "near" Shaw. _East Carrol_: TU 827-30, 905, 5644-45, Lake Providence. _Grant_: TU 12735, Big Creek at Fishville, "near" Pollock. _Jefferson_: TU 5592-98, 7184, 10741, 10171, Mahogany Pond. _Lafourche_: TU 7105, 7132, 7216, 7501, 7505-07, 10087 (14), 11828-29, 11912, 11983 (2), 12123-28, 13502, 13679 (8), 13753 (22), 13766.2, Bayou Lafourche at Raceland. _Morehouse_: USNM 11631 (2), Mer Rouge. _Natchitoches_: USNM 100420, Cane River "near" Natchitoches. _Orleans_: TU 16169 (3), Audubon Park, New Orleans; USNM 029310, "near" New Orleans. _Ouachita_: TU 12916, 12954, 12970-71, 13019, 13025, Bartholomew Bayou at Sterlington; TU 5988, Monroe. _Pointe Coupee_: TU 153, 156-59, 165, 5484, 5513, 5518-19, 5646, 5648, 5651, USNM 100202-12, False River at New Roads. _Rapides_: TU 14040, Red River at Rapides. _Richland_: OU 25082. _St. Bernard_: TU 16170, Delacroix Island. _St. Charles_: TU 4539, 4579, 5224, 5990, 11928 (12), 13698 (16), Bayou Gauche between Paradis and Des Allemands; TU 5863, 11580, Bonnet Carre Spillway at Norco. _Tensas_: TU 5762, Lake St. Joseph near Newellton. _Union_: USNM 138946, Meridian Creek, 1 mi. E Conway; USNM 138947, Ouachita River, Alabama Landing. _Parish unknown_: MCZ 1622, Lake St. John (Concordia or Tensas Parish); USNM 029266, Louisiana?

MINNESOTA: _Hennepin_: AMNH 4759-60, Fort Snelling. _Lesueur_: KU 46742-43, Waterville, Lake Tetonka. _Winona_: USNM 59263-66, Homer.

MISSOURI: _Carter_: UMMZ 70737, "near" Van Buren. _Chariton_: UI 17509, Triplett. _Franklin_: USNM 55689. _Gasconade_: UMMZ 95900, Bourbeuse Creek, 8 mi. S Owensville. _Jefferson_: USNM 95405, Glaize Creek. _Lewis_: USNM 59279-80, Canton. _Miller_: UMMZ 91929, Barren Fork Tavern Creek, 5 mi. NW Iowna. _Newton_: UMMZ 82822, Shoal Creek, 12 mi. W Momit. _Phelps_: UMMZ 91930, Bourbeuse River, 10 mi. N St. James. _Reynolds_: CNHM 35392, Black River at Warner Bay Spring; USNM 55688. _Ripley_: UMMZ 90435. _Shannon_: INHS 6223, Alley Spring State Park. _St. Charles_: USNM 93089-94, Dardenne Creek, St. Peters. _St. Louis_: USNM 55685-87, Mississippi River at St. Louis. _Stone_: USNM 55684. _Washington_: USNM 55690. _Wayne_: UI 16554, Sam A. Baker State Park; UMMZ 95879, St. Francis River at Lodi. _County unknown_ (Wayne or Butler): UMMZ 83264, Clark National Forest, St. Francis River.

MONTANA: _Big Horn_: USNM 54421, Crow Agency. _Roosevelt_: USNM 58, Fort Union (locality reads "Yellowstone, Fort Union"; probably the Yellowstone River near Fort Union). _Wheatland_: UMMZ 92005, Musselshell River near Shawmut. _Yellowstone_: USNM 14535, Custer.

OKLAHOMA: _Alfalfa_: OU 9316, 2 mi. S Cherokee. _Cleveland_: OU 22973, Norman. _Delaware_: UMMZ 81476, Spavinaw. _LeFlore_: OU 16802, 1.5 mi. E Zoe. _Osage_: UMMZ 89628, Big Hominy Creek. _Pottawatomie_: OU 25175, 5 mi. SW Shawnee. _Rogers_: OU 7317, Verdigris River, 5 mi. W Claremore; UMMZ 81473-74, near Garnett, Tulsa County; UMMZ 81475, 4 mi. NE Inola. _Sequoyah_: OU 9008, 2 mi. NE Gore; TU 13885, Little Vian Creek, 1 mi. E Vian. _Texas_: OU 5005, 5 mi. SE Guymon. _Tulsa_: TU 17061, Bird Creek "near" Skiatook, Osage County. _Woods_: CHNM 11809, Waynoka; OU 9432, 2.5 mi. W Waynoka; OU 9579, 9581-82, 1 mi. S Waynoka.

TEXAS: _Hansford_: TTC 719, 10 mi. S, 2 mi. W Gruver. _Hutchinson_: TTC 1090, Carson Creek, Turkey Track Ranch.

WYOMING: _Goshen_: USNM 7648, Fort Laramie. _Weston_: UMMZ 78080, Beaver Creek.

NO DATA: CNHM 21687-88, 22925. SM 142 (locality of Waco, McLennan County, Texas, believed in error). USNM 7649, 11625, 19622-23, 36412 (Illinois River).

_Records in the literature._--ARKANSAS: _Benton_: (Dowling, 1957:37). _Chicot_: Lake Chicot. _Clark_: Terre Noir Creek, 13 mi. W Arkadelphia. _Garland_: Ouachita River, Mountain Pine (Conant and Goin, 1948:7). _Hempstead_: _Jefferson_: (Dowling, _loc. cit._). _Lawrence_: Black Rock (Dellinger and Black, 1938:46). _Madison_: _Scott_: _St. Francis_: (Dowling, _loc. cit._). _Washington_: near Greenland (Dellinger and Black, _loc. cit._).

COLORADO: _Boulder_: Boulder Creek, E Boulder; Boulder Creek, 6 mi. S and 1 mi. E Longmont. _Larimer_: Cache la Poudre River. _Logan_: 8 mi. NE Sterling. _Morgan_: Platte River "near" Fort Morgan. _Otero_: Purgatoire River at Higbee. _Prowers_: Arkansas River at Lamar. _Weld_: Poudre River "near" Greeley; Evans. _Yuma_: Bonny Dam, Republican River (Maslin, 1959:24-25).

IOWA: _Dickinson_: Little Sioux River, Okoboji Twp. (Blanchard, 1923:24). _Story_: Skunk River, 5 mi. NNE Ames (Conant and Goin, 1948:9).

KANSAS: _Allen_: Petrolia (KKA). _Barber_: 7 mi. S Sun City. _Butler_: 3 mi. SE Augusta (Burt and Hoyle, 1934:198). _Chase_: 10 mi. SW Olpe; 7 mi. SW Saffordville (Breukelman and Smith, 1946:112). _Cherokee_: tributary of Spring River, 1 mi. N Riverton (Hall and Smith, 1947:451). _Coffey_: (Smith, 1956:160, symbol on map). _Cowley_: 11 mi. SE Winfield (Stejneger, 1944:55). _Crawford_: Pittsburg (Hall and Smith, _loc. cit._). _Doniphan_: "near" Geary (Linsdale, 1927:81). _Elk_: (Smith, _loc. cit._). _Ellis_: Big Creek (Brennan, 1934:190); Ellis (Conant and Goin, 1948:2). _Franklin_: Middle Creek, SE part of county (Gloyd, 1928:135). _Greenwood_: (Stejneger, _op. cit._:54). _Leavenworth_: Missouri River "near" Fort Leavenworth (Brumwell, 1951:208). _Lyon_: 5 mi. E Emporia (Breukelman and Smith, _loc. cit._). _Marion_: (Smith, _loc. cit._). _Meade_: Meade County State Park, _ca._ 13 mi. SW Meade (Tihen and Sprague, 1939:505). _Ness_: 5.5 mi. NW Ness (Breukelman and Smith, _loc. cit._). _Osage_: Marais des Cygnes River; Long and Jordan Creeks (Clarke, 1958:21). _Reno_: 6 mi. E Turon. _Sedgwick_: 2 mi. NE Cheney (Burt, 1935:321). _Sheridan_: State Lake 7 mi. NE Quinter, Gove County (Breukelman and Smith, _loc. cit._). _Wabaunsee_: Dragoon Creek at Harveyville (Clarke, 1956:215). _Wallace_: (Burt, 1933:208). _Wilson_: Fall River, 1/2 mi. S Neodesha (Clarke, _loc. cit._).

MINNESOTA: _Anoka_: _Benton_: _Chisago_: (Breckenridge, 1944:184, symbols on map). _Crow Wing_: (Breckenridge, _op. cit._:185). _Dakota_: (Hedrick and Holmes, 1956:126). _Goodhue_: (Breckenridge, _op. cit._:184, symbol on map). _Hennepin_: Minneapolis; Lake Minnetonka (Breckenridge, _op. cit._:187); 5 mi. N. Minneapolis (Breckenridge, 1955:5). _Houston_: Root River near Hokah. _Lesueur_: Lake Washington (Hedrick and Holmes, _loc. cit._). _Meeker_: Swan Lake (Breckenridge, 1957:232). _Pine_: (Breckenridge, 1944:185). _Ramsey_: _Rice_: _Sherburne_: _Stearns_: (Breckenridge, _op. cit._:184, symbols on map). _Washington_: just north of Stillwater (Hedrick and Holmes, _loc. cit._). _Winona_: Winona (Breckenridge, _op. cit._:187). _Yellow Medicine_: (Breckenridge, _op. cit._:185). _County unknown_ (Goodhue or Wabasha): Lake Pepin (Breckenridge, _op. cit._:184).

MISSOURI: _Boone_: east of Ashland (Henning, 1938:92). _Jackson_: Missouri River "near" Atherton (Anderson, 1942:219). _Jefferson_: Mississippi River "near" mouth Glaize Creek at Sulphur Springs; Glaize Creek at Barnhart (Boyer and Heinze, 1934:199). _St. Clair_: Osage River "near" Osceola. _Vernon_: Marmaton River, 7 mi. N Moundville (Conant and Goin, 1948:9).

MONTANA: Yellowstone River (Conant and Goin, 1948:9).

NEBRASKA: _Adams_: 1 mi. N Ayr (Hudson, 1942:101). _Dawson_: 2 mi. SE Gothenburg (Gehlbach and Collette, 1959:142). _Franklin_: 2 mi. SW Naponee. _Gage_: 1 mi. W Barnston. _Hitchcock_: 3 mi. E Stratton. _Holt_: Elkhorn River "near" Atkinson. _Lancaster_: Lincoln (Hudson, _loc. cit._). _Lincoln_: 1 mi. S Sutherland (Gehlbach and Collette, _loc. cit._). _Red Willow_: 14 mi. NW McCook. _Richardson_: 2 mi. S Rulo. _Wheeler_: 2 mi. W Ericson (Hudson, _loc. cit._).

OKLAHOMA: _LeFlore_: Wister (Conant and Goin, 1948:9); Shady Pointe (KKA); Poteau River, 6.5 mi. W Heavener (Trowbridge, 1937:301). _Tulsa_: Arkansas River "near" Tulsa (Force, 1930:38).

WYOMING: _Goshen_: Platte River (Conant and Goin, 1948:10).

=Trionyx spinifer asper= (Agassiz)

Gulf Coast Spiny Softshell

Plates 37 and 38

_Aspidonectes asper_ Agassiz, Contr. Nat. Hist. United States, 1(Pt. 2):405; 2(Pt. 3):pl. 6, fig. 3, 1857.

_Trionyx spinifer asper_ Schwartz, Charleston Mus. Leaflet, No. 26:17, pls. 1-3, map 2, May, 1956.

_Platypeltis agassizii_ Baur, Amer. Nat., 22:1121, 1888.

_Type._--Lectotype, MCZ 1597; alcoholic female; locality designated as Pearl River, Columbus, Marion County, Mississippi; received from Mr. Winthrop Sargent of Natchez, Mississippi.

_Range._--Southeastern United States except peninsular Florida from the Florida Parishes of Louisiana east to southern North Carolina; Gulf Coast drainage including that of Lake Pontchartrain, Louisiana, eastward to the Apalachicola River system, and Atlantic Coast drainage including that of the Altamaha River in Georgia northward to the Pee Dee River drainage in South Carolina (see map, Fig 19).

_Diagnosis._--Juvenal pattern of black ocelli and spots, and two or more black, interrupted, lines paralleling rear margin of carapace; pale postocular and postlabial stripes often united on side of head; length of plastron short.

_Description._--Plastral length of smallest hatchling, 2.9 centimeters (USNM 134244); of largest male, 13.2 centimeters (TU 17117); of largest female, 27.0 centimeters (TU 13474).

Blackish marginal rings on carapace number two, three or four posteriorly, but decrease in number anteriorly; segments of marginal rings may extend to nuchal region; marginal rings increasingly interrupted inwardly; pattern of hatchlings having well-defined marginal rings that are not extensively interrupted (often males), or having marginal rings broken into small segments or series of dots, and pale outer margin of carapace marked by ill-defined, hazy, inner border (often females); conspicuous marginal rings often lacking on hatchling females; pale rim of carapace not four or five times wider posteriorly than laterally; carapace having blackish dots, spots, small ocelli or a combination thereof; marks on carapace of slightly varying sizes, some occasionally barlike (usually males); some hatchling females showing pale, irregular blotching on carapace, often characterized by small lichenlike figures superimposed on blackish dots.

Striping on snout variable; pale, dark-bordered stripes usually unite in front of eyes and form right or acute angle; medial dark borders of pale stripes on snout not joined anteriorly, broken into segments or dots, reduced to single median line, united to form straight line connecting anterior margins of orbits (usually with slight medial indentation), or absent; pale postocular and postlabial stripes often joined, relationship variable and on either side of head; side of head with or without dark markings, sometimes a pale subocular blotch bordered below by a dark line; pattern on dorsal portions of soft parts of body contrasting, less so on limbs of hatchlings; pattern of irregular dark marks, dark streaks usually coincident with digits; longitudinal streaks often occur on neck; elongate tail of adult males usually having well-defined, dorsolateral, pale bands with dark lower border more diffuse than upper border.

Underparts whitish often with dusky markings on rear of carapace or in region of bridge; blackish marks often on webbing and portions of soles and palms, and chin and throat.

Small conical tubercles along anterior edge of carapace on adult males; remnants of juvenal pattern usually present on carapace of large females; conical or knoblike tubercles on anterior edge of carapace of large females; accessory knoblike tubercles in nuchal region (a paravertebral pair usually most prominent), and posteriorly in middle of carapace on large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 7.0 centimeters or less, 3.87, and exceeding 7.0 centimeters, 4.94; ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.5 centimeters or less, 1.11, and exceeding 8.5 centimeters, 1.16; mean CL/PCW, 1.71; mean CL/PL, 1.45.

_Variation._--The sex of some hatchlings can be distinguished by the pattern on the carapace (see Plate 37 for different patterns), but the sex of many hatchlings cannot be distinguished on the basis of pattern.

In the early stages of this study, I thought that the pattern on the carapace differed in eastern and western populations, and that the zone of intergradation was in Alabama. Adult males from the Tombigbee-Alabama river drainage and westward were noted to have blackish spots (some slightly ocellate) intermixed with few, if any, smaller blackish dots, whereas the adult males from east of the Tombigbee-Alabama river drainage had many small, black dots intermixed with slightly larger, mostly ocellate marks (see Plate 38, left, top and bottom, for contrast); also, hatchlings from western populations were never observed to have four marginal rings. On the basis of pattern, I would have thought that the individual having many ocelli, that lacks correct locality data and that is photographed by Stejneger (1944:Pl. 26), came from Georgia or South Carolina; but, the pattern (_op. cit._:Pl. 27) of a specimen, probably an adult male, from South Carolina, resembles the pattern on adult males from Louisiana. The differences noted above are probably due to individual variation rather than geographic variation.

Color notes taken from life of a freshly-killed adult male (TU 16071, Louisiana) are: carapace olive, spots blackish, outer rim buff; top of head olive, postocular and postlabial stripes yellow with blackish borders, stripes on snout buff with blackish borders; dorsal ground color of soft parts of body pale olive-green, larger marks blackish, ground color laterally toward juncture of pattern and immaculate undersurface, and toward insertions of neck and limbs becoming yellowish; webbing on hind limbs having reddish tinge; dorsolateral bands on tail yellow with blackish borders; undersurface whitish; chin and throat olive-green with blackish marks; becoming buff then whitish posteriorly.

Occasional specimens have only one definite dark line paralleling the rear margin of the carapace. Schwartz (1956:16) reported that Charleston Museum No. 55.159.26 has only one solid line at the margin of the carapace, and I received an adult male (KU 47120) reported to have come from the Pearl River that is aberrant in not having more than one dark marginal line. USNM 95191, a large stuffed female from the Pearl River is mentioned by Stejneger (1944:59, Pl. 17) as having marks that "assume the form of short lines parallel with the submarginal ring"; I examined this specimen and noted that it had only one dark marginal line. Stejneger (_op. cit._:64) mentioned another from the Pearl River drainage, and Crenshaw and Hopkins (1955:20) wrote that some individuals from Georgia have only one dark marginal line. Presumably MCZ 1606 (now in the Albany Museum) recorded by Stejneger (_op. cit._:52) as _Amyda s. spinifer_ from Columbus, Georgia, is another specimen.

Some skulls of soft-shelled turtles from streams of the Atlantic Coast drainage, including the skull of the holotype of _Platypeltis_ (= _Trionyx_) _agassizi_ Baur (MCZ 37172, Pl. 54), show at least two differences from other skulls of _asper_ and from those of other subspecies of _T. spinifer_. Figure 20 shows that skulls of _agassizi_ tend to have slightly smaller internal choanae (ratio IC/MB) than those of _T. spinifer_ and _T. ferox_; there is seemingly little difference between skulls of _ferox_ and _spinifer_, and little, if any, ontogenetic variation. Figure 21 shows that most skulls of the _agassizi_-form that exceed 43.0 millimeters have a more expanded, alveolar surface of the maxilla than skulls of _spinifer_ of approximately the same size; most skulls exceeding a basicranial length of 43.0 millimeters, and certainly all skulls exceeding 50.0 millimeters are those of females. Stejneger (1944:Pl. 30) also has provided photographs of a skull of the _agassizi_-form. It is of interest that of the 12 _agassizi_-form skulls (MCZ 37172; USNM 8708, 029034, 51981, 66859, 71681, 91282, 91310-11, 92521, 92583-84) that I examined some resemble _ferox_ (Neill, 1951:9) in having the alveolar surfaces of the jaws broadened, and the greatest width at the level of the quadratojugal (Table 3, Plate 54); also, the localities of all 12 skulls are within the geographic range of _ferox_. Skulls of _ferox_, however, have conspicuously broadened alveolar surfaces of the jaws only when they exceed in length the largest skulls of _agassizi_. The differences of skulls of the _agassizi_-form possibly reflect isolation in the Atlantic Coast drainage, and an adaptation in feeding habits. So far as I can ascertain, individuals occurring in rivers of the Atlantic Coast drainage in Georgia and South Carolina (referable to _agassizi_) do not differ consistently in external characters from individuals of _T. s. asper_ that occur westward in the Apalachicola drainage.

_Comparisons._--_Trionyx s. asper_ can be distinguished from all other subspecies of _T. spinifer_ by usually having more than one black line paralleling the rear margin of the carapace. This character and the frequent fusion of the postlabial and postocular stripes on the side of the head distinguish _asper_ from _spinifer_ and _hartwegi_. _T. s. asper_ differs from _pallidus_, _guadalupensis_ and _emoryi_ in having blackish spots and ocelli on the carapace, and lacking whitish dots or tubercles. _T. s. asper_ resembles _spinifer_, _hartwegi_ and _pallidus_ but differs from _guadalupensis_ and _emoryi_ in having conical tubercles along the anterior edge of the carapace in large females. For additional differences see accounts of other subspecies.

Of the subspecies of _T. spinifer_, _asper_ has a proportionately wide head that is closely approached in the subspecies _guadalupensis_ and _emoryi_; _T. s. asper_ differs from _guadalupensis_ and _emoryi_ in having a wider carapace, and resembles _hartwegi_ and _spinifer_, but differs from the other subspecies in having the carapace widest at a plane approximately one-half way back on the carapace. _T. s. asper_ differs from the other subspecies in having the shortest plastron.

_Remarks._--Stejneger (1944:72-74) has discussed the history of Baur's _Platypeltis agassizi_. Briefly, Agassiz's description of _Platypeltis ferox_ wherein he (1857:402) states that "The young ferox [Pl. 6, fig. 3] has two or three concentric black lines separating the pale margin ...," was applicable to _T. s. asper_. Agassiz mentioned also that the young of his _Aspidonectes asper_ (_op. cit._:406) "as in Platypeltis ferox, ... has ... two or three black lines separating the pale rim of the posterior margin, ..."; however, _A. asper_ was distinguished chiefly by the "... prominent warts of the bony plates (_loc. cit._)." Because the description of the pattern of _ferox_ resembled that of _asper_, the validity of _asper_ was not agreed upon by all workers. Boulenger (1889:245, footnote 1) referred to _asper_ as a species that required "... further investigation."

Baur (1888:1121) realized that Agassiz's description of _ferox_ was not that of _Testudo ferox_ Schneider, and regarded the description of Agassiz as applying to a new species, which he named _Platypeltis agassizii_; Baur (_op. cit._:1122) also recognized _asper_, referring it to the genus _Aspidonectes_. Baur designated a specimen from Georgia (the only individual seen by him) as the type of _agassizi_ (Stejneger, _op. cit._:73, footnote); this specimen is now MCZ 37172. Five years later (1893:218), Baur discussed generic relationships of trionychids, seemingly only on the basis of skulls (holotype of _agassizi_ not mentioned), and referred _agassizi_ to the resurrected genus _Pelodiscus_ Fitzinger, 1835, which was distinguished from the other two American genera that Baur recognized (_Platypeltis_ and _Amyda_) by having the "Posterior nares reduced in size by the inner and posterior extension of the maxillaries." Baur also transferred _asper_ to the genus _Platypeltis_, and restricted the type locality of that species to "Lake Concordia, La." (_op. cit._:220); the type locality of _agassizi_ was restricted to "Western Georgia" (_loc. cit._).

The name-combination, _Pelodiscus agassizi_, was not generally accepted. Hay (1892:144) and Siebenrock (1924:188) referred _agassizi_ to the genus _Trionyx_. Hay regarded _agassizi_ as a full species (see discussion by Stejneger, 1944:73), whereas Siebenrock considered it a subspecies of _spiniferus_; both authors regarded _asper_ as a synonym of _agassizi_. Neither _asper_ nor _agassizi_ was mentioned in the first three editions of the Check List of North American Amphibians and Reptiles (Stejneger and Barbour, 1917, 1923, 1933); the same authors in the fourth (1939:171, 172) and fifth editions (1943:212, 213) listed _agassizi_ as a full species, and _asper_ as a subspecies of _spinifera_. Stejneger (1944) used the same arrangement as set forth in the fourth and fifth editions of the Check List, and distinguished _agassizi_ on the basis of cranial characters, namely, the small size of the internal choanae, the greater width of the alveolar surface of the lower jaw, and the position of the suture between the palatine and basisphenoid relative to the posterior edge of the temporal fossa. Neill (1951:9) regarded the peculiarities of the _agassizi_-type skull as inconstant, but recognized _agassizi_ (and _asper_) as a subspecies of _ferox_. Crenshaw and Hopkins (1955) showed that _asper_ did not intergrade with _ferox_. Schwartz showed that _agassizi_ did not intergrade with _ferox_, and regarded _agassizi_ as a synonym of _T. s. asper_ (1956:17), but stated that _agassizi_ possessed "wider crushing surfaces on the maxillae than does _T. s. asper_, even when skulls of the same size and sex are compared" (_op. cit._:9).

The holotype of _Platypeltis agassizi_ (MCZ 37172) is a dried adult female consisting of shell, skull and limb bones; the carapace is approximately 300 millimeters long (Schwartz, _loc. cit._). I have examined only the skull of MCZ 37172 (Plate 54), and it is the largest of 12 _agassizi_-type skulls I have seen. The basicranial length is 72.5 millimeters, and the greatest width, which occurs at the level of the quadratojugals, is 52.9 millimeters. The _agassizi_-type skulls have been discussed under the subsection on variation.

The type locality of _T. s. asper_, Lake Concordia, Louisiana (lower Mississippi River drainage) as restricted by Baur (1893:220), is in an area of intergradation of three subspecies of _Trionyx spinifer_ where most individuals are not typical of _asper_. The syntypes, the designation of MCZ 1597 as a lectotype, and Pearl River, Columbus, Marion County, Mississippi, as the type locality have been discussed elsewhere (Webb, 1960).

The range of _T. s. asper_ overlaps that of _T. ferox_ in Georgia and South Carolina. The two species remain distinct in the area of overlap of their geographic ranges (Crenshaw and Hopkins, 1955:16; Schwartz, _op. cit._:5). _Trionyx s. asper_ intergrades with _T. s. hartwegi_ and _T. s. spinifer_ in the lower Mississippi Valley (Conant and Goin, 1948:11).

However, there are few specimens available that indicate intergradation of _asper_ with the _spinifer-hartwegi_ complex in the lower Mississippi River drainage; this may be due to the fact that _asper_ inhabits waterways that do not drain into the Mississippi River. Perhaps intergradation is more prevalent than the morphological basis that I have relied upon indicates; in any event, there are few specimens that have more than one dark marginal line (which is the only character that is unique for _asper_) from the lower Mississippi drainage. A young male (TU 11928.9) from Bayou Gauche between Paradis and Des Allemands, St. Charles Parish, Louisiana, has a pattern on the carapace resembling that of _asper_; several other small softshells (TU) are available from the same locality but none shows more than one dark marginal line. Another specimen (USNM 95192), a young female from a barrow pit of the Big Black River (Mississippi River drainage), Madison County, Mississippi, resembles _asper_ in having more than one marginal ring. Of three large females from Moon Lake, an ox-bow of the Mississippi River in Coatopa County, Mississippi (AMNH 5285-86, 5289), only 5289 shows evidence of two marginal lines. USNM 73669 (Greenwood, LeFlore County, Mississippi) also indicates intergradation in that the spots tend to be linear just inside the dark marginal line, but the specimen more closely resembles the _hartwegi-spinifer_ complex rather than _asper_.

There seems to be little adumbration of the dark marginal lines of _asper_ in populations from the lower Mississippi River drainage. Blackish spots and ocelli vary in size and there are many kinds of pattern on the carapace. Soft-shelled turtles inhabiting the Mississippi River and its tributaries in Louisiana and Mississippi certainly represent an intergrading population of _spinifer_ and _hartwegi_, and, to a lesser extent, of _asper_. Soft-shelled turtles inhabiting the Pearl River drainage and rivers that drain into Lake Pontchartrain immediately adjacent to the east are predominantly _asper_.

Specimens having localities from the Pearl River and Lake Pontchartrain drainages are listed under the account of _asper_ and are referred to that subspecies on the distribution map; specimens from the Mississippi drainage in Mississippi are referred to _spinifer_.

One specimen (UMMZ 59198, Bradley County, Tennessee), from the Tennessee River drainage where _T. s. spinifer_ occurs, deviates markedly from _spinifer_ and suggests intergradation. UMMZ 59198, plastral length 4.8 centimeters, has ocelli in the center of the carapace only two millimeters in diameter, a distinct but interrupted, second marginal ring consisting of spots, and the pale postlabial and postocular stripes in contact on both sides of the head.

_Specimens examined._--Total 110, as follows: ALABAMA: _Barbour_: UMMZ 113038, Chattahoochee River, Eufala. _Cherokee_: ANSP 24592, "near" center of Terrapin Creek. _Conecuh_: UMMZ 70736, Murder Creek, Castleberry. _Escambia_: TU 15823, Escambia River, 1 mi. N Sardine; UMMZ 70734, Escambia River at Flomaton. _Henry_: TU 15630, 3 mi. NW jct. Echo Farm Rd. and Rt. 136 on Echo Farm Rd. _Lowndes_: UMMZ 67759, Pintlalla Creek. _Mobile_: MCZ 1608 (2), 1608A, Mobile. _Sumpter_: USNM 83996, 3 mi. SE Coatopa. _Tuscaloosa_: TU 14673 (5), Black Warrior River, 17.5 mi. SSW Tuscaloosa; UA 52-1085, Cottondale. _Walker_: KU 50843, 50851, TU 17137, Mulberry Fork, Black Warrior River, 9 mi. E Jasper.

FLORIDA: _Calhoun_: KU 50837-38, Chipola River, 4 mi. N Scott's Ferry; TU 16689 (4), Chipola River "near" Blountstown. _Escambia_: TU 13474, 15869 (3), 16584, Escambia River, 1.2 mi. E Century. _Okaloosa_: TU 15661, Blackwater River, 4.3 mi. NW Baker on Route 4. _Santa Rosa_: AMNH 44621, Blackwater River, Milton. _Walton_: UMMZ 110421, Pond Creek, 4 mi. SW Florala, Covington County, Alabama.

GEORGIA: _Baker_: TU 15889 (3), USNM 134243-48, Flint River "near" Newton; USNM 30822. _Baldwin_: USNM 8708, Milledgeville. _Bryan_: TU 15090, Canouche River, 2.3 mi. W Groveland. _Chatham_: USNM 51981, 92583-84, Savannah. _Chattooga_: UMMZ 113037, tributary of Chattooga River, Lyerly. _Decatur_: KU 50839-42, Flint River, 1.5 mi. S Bainbridge. _Fulton_: UMMZ 53037, Roswell. _Lincoln_: USNM 91282-83, above Price Island, Savannah River. _Murray_: UMMZ 59196, 9 mi. N Spring Place. _Pulaski_: TU 14882, Ocmulgee River, 4.3 mi. SE Hawkinsville. _Richmond_: USNM 66859, Augusta. _Whitfield_: UMMZ 74209, Cohulla Creek, Prater's Mill "near" Dalton. _County unknown_: MCZ 37172; UMMZ 109864, Flint River at mouth of Dry Creek; USNM 029034.

LOUISIANA: _East Baton Rouge_: LSU 11, 1643-44, City Park Lake in Baton Rouge; TU 17237, Amite River "near" Baton Rouge. _St. Tammany_: TU 6356, headwater creek of Bayou Lacombe; TU 16071, USNM 66147, mouth of Tchefuncta Creek in Lake Pontchartrain. _Tangipahoa_: TU 13623, 3.1 mi. W Hammond; USNM 68054, Robert. _Washington_: KU 50840, 50846, TU 17117, Pearl River at Varnado. _Parish unknown_ (East Baton Rouge or Tangipahoa): UMMZ 95614, Manchac.

MISSISSIPPI: _Chickasaw_: USNM 115981, Chookatonkchie Creek. _Clarke_: USNM 79350-51, 1 mi. W Melvin, Choctaw County, Alabama; USNM 100805, Enterprise. _Forrest_: WEB 55-586, 1 mi. S Hattiesburg. _Hancock_: AMNH 46780; WEB 54-651, Hickory Creek "near" Kiln. _Lauderdale_: UMMZ 74681, 9 mi. W Meridian; UMMZ 90130, Lake Juanita, 15 mi. W Meridian. _Lawrence_: KU 47120, TU 17307.1, Pearl River, 9 mi. S Monticello; USNM 7653-54, Pearl River at Monticello. _Lee_: CM 31904, Verona; USNM 115979, Cower's Area near Guntown. _Madison_: USNM 95191, 95193-94, Pearl River. _Marion_: MCZ 1597, Pearl River at Columbus (designated type locality). _Pearl River_: CM 21100, Pearl River, 20 mi. W Poplarville; TU 14362, Hobolochito Creek, 1 mi. N Picayune. _Perry_: WEB 55-580, Beaver Dam Creek, 1 mi. N Richton. _Walthall_: KU 50844, Bogue Chitto River, Dillon.

SOUTH CAROLINA: _Abbeville_: USNM 7650, Abbeville? (reported by Pickens, 1927:113; locality considered in error by Stejneger, 1944:50; USNM 7650 having only one dark marginal line paralleling rear margin of carapace is possibly an aberrant specimen--see page 495 of present account). _Greenwood_: USNM 71681, 73668, Greenwood. _McCormick_: USNM 91310-12, Savannah River, 5 mi. W Plum Branch; USNM 92521, near Parksville. _Richland_: AMNH 70724-25, Broad River, Columbia.

NO DATA: USNM 8359 (erroneously reported from Madison, Indiana by Yarrow, 1882:29 and Hay, 1892:145; see discussion by Cahn, 1937:200, and Stejneger, 1944:73-75); USNM 131859.

_Records in the literature._--ALABAMA: _Coffee_: Elba (KKA). _Marengo_: Tombigbee River near Demopolis. _Mobile_: Fig Island (Löding, 1922:47).

FLORIDA: _Jackson_: Chattahoochee River, 8 mi. SE Butler. _Leon_: Ochlocknee River, NW of Tallahassee (Goin, 1948:304).

GEORGIA: _Bartow_: Etowah River below Allatoona Dam, _ca._ 4 mi. ESE Cartersville (Crenshaw and Hopkins, 1955:15). _Berrien_: (Knepton, 1956:324). _Emanuel_: Ogeeche River (Schwartz, 1956:19). _Fulton_: Nancy Creek, Atlanta (Dunston, 1960:278). _Gwinnett_: _Irwin_: (Knepton, _loc. cit._). _Jenkins_: Ogeeche River near Buckland Creek jct., 2.5 mi. S Millen. _Liberty_: Camp Stewart, 4 mi. N Hinesville. _Morgan_: Lake Rutledge (Schwartz, _loc. cit._). _Muscogee_: Columbus (Stejneger, 1944:52). _Wayne_: Altamaha River, 5 mi. N Mt. Pleasant (Schwartz, _loc. cit._). _Wilcox_: Ocmulgee River, 3-4 mi. SSE Abbeville (Crenshaw and Hopkins, _op cit._:16, footnote; Schwartz, _loc. cit._).

MISSISSIPPI: _George_: Whiskey Creek (Cook, 1946:185). _Harrison_: near Biloxi. _Jackson_: Pascagoula Swamp, _ca._ 40 mi. E. Biloxi (Corrington, 1927:101). _Jones_: Eastabuchie. _Lee_: Cain Creek Bottom. _Lincoln_: Old Brook Creek. _Lowndes_: Tombigbee River, Camp Henry Pratt and Columbus; Lake Park, Columbus. _Pearl River_: 21 mi. SW Poplarville; 10 mi. W Poplarville; 4 mi. W Poplarville. _Wayne_: Trigg Area (Cook, _loc. cit._).

NORTH CAROLINA: _Mecklenburg_: Catawba River near Charlotte (Schwartz, 1956:20).

SOUTH CAROLINA: _Aiken_: Savannah River, 10 mi. SW Jackson. _Allendale_: Savannah River, Fennell Hill, 2 mi. S US 301. _Anderson_: Pendleton. _Bamberg_: South Edisto River, Cannon's Bridge, 5 mi. from Bamberg. _Berkeley_: 2.5 mi. W Pinopolis. _Charleston_: Charleston. _Clarendon_: Upper Lake Marion at US 301; Lake Marion, 13 mi. SW Manning; 3.3 mi. S Jordan; 6.3 mi. S Jordan; Wyboo Creek, 8.5 mi. from Manning. _Colleton_: Edisto River (Schwartz, 1956:19-20). _Darlington_: Pee Dee River, Society Hill (Stejneger, 1944:72). _Dorchester_: Edisto River, 17 mi. from Summerville; Edisto River, 14 mi. W Summerville; Edisto River, 2.5 mi. S Hart's Bluff. _Fairfield_: 1 mi. N Peak, Newberry County. _Georgetown_: North Santee River, 1 mi. above US 17. _McCormick_: Little River near McCormick; Little River, 3 mi. NE Mt. Carmel. _Laurens_: Enoree River, 3 mi. S Cashville, Spartanburg County; Enoree River, 9.4 mi. N Clinton. _Orangeburg_: Edisto River, Orangeburg. _Saluda_: Batesburg; Lake Murray; Little Saluda River; 5 mi. from Saluda. _County unknown_: Upper Lake Santee (Schwartz, _loc. cit._).

=Trionyx spinifer emoryi= (Agassiz)

Texas Spiny Softshell

Plates 43, 44

_Aspidonectes emoryi_ Agassiz (in part), Contr. Nat. Hist. United States, Vol. 1, Pt. 2, p. 407; Vol. 2, Pt. 3, pl. 6, figs. 4-5, 1857.

_T[rionyx] s[pinifer] emoryi_ Schwartz, Charleston Mus. Leaflet, No. 26, p. 11, 1956.

_Type._--Lectotype, USNM 7855; alcoholic (sex undetermined); obtained from the Río Grande near Brownsville, Texas, in the course of the Mexican Boundary Survey under the command of Colonel Wm. H. Emory.

_Range._--Southwestern United States and northern México; the Río Grande drainage in Texas, New Mexico and northern México; the Río San Fernando and Río Purificación drainages in northeastern México; the Colorado River drainage in Arizona, New Mexico, and southern Nevada (see map, Fig. 19).

_Diagnosis._--Juvenal pattern of white dots, not encircled with dusky or blackish ocelli, confined to posterior third of carapace; pale rim of carapace conspicuously widened, four to five times wider posteriorly than laterally; a dark triangle in front of eyes, base line connecting anterior margins of orbits; pale postocular stripe interrupted leaving conspicuous pale, usually dark-bordered, blotch just behind eye.

_Description._--Plastral length of smallest hatchling, 2.5 centimeters (USNM 7632); of largest male, 13.0 centimeters (KU 2914, 3125, 3150); of largest female, 22.0 centimeters (TNHC 8023, 8104).

Carapace pale brownish or tan, lacking whitish dots on anterior half; whitish dots confined to posterior third of carapace, sometimes lacking posteriorly, especially on juveniles; small, blackish dots rarely occurring on surface of carapace, usually confined to margins when present; pale rim of carapace four to five times wider posteriorly than laterally.

Pattern on snout rarely variable, consisting of pale stripes extending forward from eyes that have only their outer borders darkened and a straight or slightly curved, dark line that connects anterior margins of orbits; few, if any, dark markings in subocular and postlabial region; pattern on side of head having few contrasting marks, often of nearly uniform coloration; postocular stripe usually interrupted; anterior segment of postocular stripe just behind eye usually dark-bordered; posterior segment usually not dark-bordered or sharply distinguished from background; pattern on dorsal parts of soft parts of body contrasting, of relatively small dark marks; dark streaks often coincident with digits.

Underparts whitish, occasionally having blackish dots or smudges on posterior part of carapace, in region of bridge, or on lateral parts of chin and throat; few dark marks often on webbing of limbs and on palms and soles.

Small, flattened or wartlike, tubercles that occasionally have sharp tips along anterior edge of carapace on adult males; tubercles flattened, scarcely elevated, never conical along anterior edge of carapace on large females; whitish, knoblike tubercles often present posteriorly in middle of carapace and in nuchal region on large females; mottled and blotched pattern sometimes contrasting on carapace of large females; whitish dots of juvenal pattern often visible through overlying blotched pattern of large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 7.0 centimeters or less, 3.68, and exceeding 7.0 centimeters, 5.19; ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.5 centimeters or less, 1.17, and exceeding 8.5 centimeters, 1.27; mean CL/PCW, 2.18; mean HW/SL, 1.43; mean CL/PL, 1.37.

_Variation._--Ten topotypes (six males, three females, one juvenile) from Brownsville, Texas (BCB 7465-73, 7564), have the following characteristics: pale rim widened posteriorly as described above; females (plastral lengths 9.8, 10.2 and 11.7 cm.) having blackish marks in pale rim, which are absent in males of corresponding size; interrupted postocular stripe with pale blotch behind eye; postocular pale blotch having blackish borders or not; dark triangular mark on snout in front of eyes; white dots present only on posterior third of carapace; carapace of females grayish, blotched pattern not contrasting; carapace of males paler, greenish-gray; undersurface immaculate except 7468 and 7472 that have blackish flecks at bridge and, on 7472, blackish marks that extend posteriorly onto ventral surface of carapace; tubercles along anterior edge of carapace flattened and rounded in adult males, more knoblike in females; largest specimen, BCB 7472, female, plastron 11.7 centimeters long.

_T. s. emoryi_ varies more than any other subspecies of _Trionyx spinifer_. A large series of males and females (KU) from the Salt River (Colorado River drainage), near Phoenix, Arizona, is characterized by many adult males having indistinct white dots on posterior half of carapace; blotching on carapace of females of contrasting lichenlike figures, but usually non-contrasting and pale brownish or tan; pale rim of carapace distinct from ground color of carapace in largest female (KU 2905, plastron 21.5 cm. in length), but having dark or dusky markings: dark interorbital stripe often lacking. AMNH 58370 (Nevada) and UMMZ 92006 (Arizona) also have the dark line connecting the anterior margins of the orbits interrupted; seemingly the dark interorbital line is most often interrupted in those softshells inhabiting the Colorado River system of Nevada and Arizona.

Other variant individuals are: TU 14453.2, 14462 and 3696 having the plastron extending slightly farther forward than the carapace, thus resembling _T. ferox_; UMMZ 54021 and CNHM 39999, hatchlings, lacking distinct whitish dots on posterior half of carapace; UI 43509 and KU 39991 having stained (brown or blackish) claws; and, CNHM 6810, an adult male, lacking a spinose (sandpapery) carapace. I am unable to discern geographic variation in these or other characters.

The ground color of the carapace on some individuals from the Pecos River (TU, Terrell County, Texas) is grayish and in contrast with the pale rim (Pl. 44). UI 43509 from the Río Florida, La Cruz, Chihuahua, a female, has a dark brownish carapace with little evidence of a blotched pattern except on the pale rim of the carapace. A female and adult male from the Río Sabinas, Coahuila (MSU 905-06), also show considerable darkening on the dorsal surfaces; the pale rim is evident but not in sharp contrast to the coloration of the carapace. Notes taken on the freshly-killed Sabinas individuals are: male--carapace olive-gray; dorsal surface of soft parts of body olive-green to grayish, a bright yellow suffusion on limbs and neck; female--carapace and soft parts of body dark olive, laterally pale yellow; the plastron extends slightly farther forward than the carapace in both sexes.

Notes on coloration (judged to be the most common or "normal" type) of living _emoryi_ from the Río Mesquites, central Coahuila, are: Adult male (KU 53753)--pale rim butterscotch yellow; marginal line blackish; whitish dots on pale brown or tan carapace; soft parts of body olive or olive-green, slightly darker on head and paler (yellowish) on hind limbs; pale areas on side of head pale yellow, having tint of orange on neck; ventral surface white, yellow laterally on neck. Adult female (KU 53754)--carapace having contrasting blotched and mottled pattern of pale browns and tans; soft parts of body olive brown, darker brown blotching on head; dorsal surface of limbs olive-green having pale areas lemon yellow and webbing butterscotch yellow; side of neck and head, chin and throat pale lemon yellow; ventral surface white having slight red tinge to groin and soft parts posteriorly; underside of carapace near edge pale yellow.

Softshells from the Río Grande in the Big Bend region of Texas, and the Río Conchos in Chihuahua differ from other specimens of _emoryi_. Fifteen adult males, KU 51187-201 (no females in sample), were taken from the mouth of the Río San Pedro at Meoquí, Chihuahua (see KU 51194, Pl. 44). They are noteworthy because of a conspicuous orange or orange-yellow on the side of the head. Another relatively consistent character is the blackish tip of snout (excepting 51199), although the degree (palest on 51190) and extent of pigmentation posteriorly on the snout is variable. Eleven males, KU 51175-85, from approximately 100 miles northeastward in the Río Conchos near Ojinaga, Chihuahua, also have the bright orange on the side of the head; the tip of the snout is not blackish, although in some it is slightly darkened. Three females, KU 51174, 51186 (from Ojinaga) and 51173 (from 8 mi. S, 16