Part 2

The fourth premolar has a very curious shape. The blade of this tooth resembles the crown of the third, but is smaller. It is inserted by three fangs, the disposition of which is opposite to that in _Canis_, the internal, being on the same transverse line as the posterior external, instead of the anterior, as in _Canis_. From the internal fang arises a sharp cusp, which is nearly as large as the blade of the tooth, the two are connate at base. The anterior face of the crown is much worn, and there is a small anterior heel formed by the basal ridge. The cingulum is complete all around.

The _maxillary_ does not show the outward bulge at the third premolar, which is so marked in the fox. The alveolus is straighter, and the palatine plates are comparatively thicker and flatter. The infraorbital foramen is oval, and not so much compressed as in the fox, to which it corresponds very nearly in position, though situated slightly forward as in _Hyænodon_.

_Measurements._

_Upper Jaw._ M.

Length of third premolar ·007 Breadth of third premolar ·004 Length of fourth premolar ·007 Breadth of fourth premolar ·007

_Lower Molars_, from Dr. Leidy.

Length of last premolar ·0075 Length of first molar ·009

These exhibit nearly the same proportionate size as in the gray fox.

_Genus_ ----. _Species_ ----.

_Sacrum_ (Plate IX., Fig. 8).--This peculiar sacrum is composed of only one true vertebra; there may have been one or more pseudo-sacrals, but this is not certain.

The centrum is very long, strongly depressed, and straight on the inner margin, not curved as in the sacrum of most mammals. The anterior articular face is much depressed, and is one third larger than the posterior. The neural canal is low and subtriangular, resembling very much that of _Canis_. The pleuropophysial plates for articulation with the ilia are large and stout. The laminæ are heavy and concave on their upper side, supporting a very long, stout spine, which is retroverted and decidedly tuberous at the end.

The pedicles are deeply notched behind; and on the fore part, just inside the metapophyses, there is a deep fossa.

The chief features of this sacrum are decidedly carnivorous; but to what genus or family it should be referred we are unable to say.

It has some of the characteristics of _Canis_, but the length and retroversion of the spine, as well as the size of the centrum, prevent this classification. In the general form of the pleuropophysial plates it approximates to the _seals_; while in its angle and curvature, it partakes of the character of the _Ursidæ_.

The chief point of interest in this fossil centres in the fact that it was found only a few feet from the brain cast that is described below.

_Measurements of Sacrum._

M. Length of centrum ·031 Long diameter of anterior articular face ·024 Long diameter of posterior articular face ·017 Width of neural canal ·019 Height of neural canal ·011 Length of neural spine ·036 Extreme width of sacrum ·052

MEGENCEPHALON.

Megencephalon primævus. _Gen. et spec. nov._

In close proximity to the pelvis of the _Uintatherium Leidianum_, in one of the upper beds we found an intracranial cast, separate from the bone which had enclosed it, and in such preservation as to warrant a partial determination, at least, of the type to which it belonged. Wishing to obtain as full information as the nature of the cast permitted, we put it in the hands of Dr. Spitzka, of New York, who kindly undertook an examination, and sent us the following as the result:

"Sir: The specimen submitted to me is the intracranial cast of some species of Placental Mammals. The cranium had been subject to the influences of the atmosphere, etc., for a considerable period preceding the formation of the cast, and therefore the cast reflects the sutural dislocations which occurred in consequence. The base of the brain cast it is not advisable to attempt to expose, on account of the treacherous nature of the material. The convolutions corresponding to the internal aspect of the _Os temporale_ have not been clearly demarcated by the bone surface. The two narrow eminences on it are casts of the grooves of the middle meningeal arteries. The convolutions of the occipital surface had been well marked, but somewhat obliterated through denudation, etc. The important region bordering on each side of the median fissure, and corresponding to the fronto-parietal suture, is unfortunately as good as destroyed; and with this destruction the key to the interpretation of the specimen is lost. However, this much can be stated with absolute certainty, that the frontal region is sufficiently well preserved to state that its convolutions do not correspond to those of the brain of the tapir, rhinoceros, hippopotamus, elephant, pig, horse, hyrax, manatus, or any ruminant or cetacean.

"They also differ in important particulars from those of the _Canidæ_, differ less from those of the _Felidæ_, still less from the _Ursidæ_, although corresponding to none of them. The outline of the cerebral cast is found in two living animals--the marine otter and the seal. But in the seal the gyri show the transverse interrupting series of sulci, characteristic of extreme brachycephaly; and it therefore cannot belong to any animal corresponding to the seal.

"The sea otter's convolutional details are unknown to me, and I believe have not yet been studied. I therefore content myself with stating that the outline of this cast corresponds to the outline of the sea otter's cranium.

"It would help us a great deal if we could decide the existence or non-existence of a bony tentorium. The sutures of this cranium, as far as I can reconstruct them, ran as in the diagram.

"We may state definitely that this was not an ursine, feline, or canine brain, nor the brain of any terrestrial viverrine. It is an open question between an _aquatic carnivore_ and an _aquatic pachyderm_; and although not placing my conclusion on an exact basis, yet, in view of the general outline, the course of the convolutions, and the course of the sutures, I incline to the former view.

"It certainly corresponds to no known brain of a living creature. In one point I was inclined to suspect it to be a pachyderm, namely, the decided asymmetry of some of the sulci, but this, by itself, is not decisive."

"Dr. Spitzka.

"308 East 123d street."

The interesting letter quoted in full above, contains as near a determination of the character of the animal to which the brain belonged, as the nature of the cast and the materials for comparison would permit. In a later report, by means of more complete comparative material, we hope to be able to reach a more satisfactory conclusion. However, as Dr. Spitzka writes, the _general outline_, the _course_ of the _convolutions_, and the _line_ of the _sutures_ offer strong presumptive evidence that the cast belongs to one of the _Aquatic carnivores_. Not far from the brain was found a sacrum, which is described above as belonging to some carnivore, though further determination was impossible. Whether there was any connection between the two is difficult to state. The presence of an aquatic carnivore in the Bridger eocene is new to science; but, aside from this, the brain is of a much higher order than previous discoveries would lead us to expect in such an early formation.

Professor Marsh's researches have led him to form the opinion that the eocene mammals had brains of a low character; but this specimen shows that this is not true of all, if it is of most of them. The convolutions are not only numerous and well marked, but they are complicated, showing the transverse as well as the longitudinal folds. To such an extent is this true that the brain will bear comparison with the very highest modern carnivorous types.

We hope to be able to give further notes upon this interesting specimen at a later date.

PERISSODACTYLA.

ANCHITHERIUM.

Von Meyer, Jahrbuch für Mineralogie, 1844, p. 298.

Anchitherium ---- ?

A small calcaneum and astragalus of equine type are provisionally referred to this genus until further material enables us to determine them with certainty.

The _astragalus_ has narrow and very oblique condyles, which are more equal in size than in _Orohippus_; the neck is very short, the internal condyle reaching to the face for the navicular; the posterior projection of this condyle is much shorter than in that genus. The articular face for the navicular is quadrate in shape and concave; the cuboid face is very narrow. The articulation with the calcaneum is made by a narrow, convex face. When the two are in position the navicular face of the astragalus is in the same horizontal line as the cuboid face of the calcaneum, thus resembling the arrangement of the horse's tarsus rather than that of _Orohippus_.

The calcaneum is a short, slender bone, having the upper and lower margins convergent toward the tuberosity, and not parallel as in _Orohippus_. The tuberosity is especially small. The face for the cuboid is very narrow.

From the articular facets of these two bones we can see that the tarsus resembled very much that of the modern horse, with a broad, short navicular, and a narrow cuboid. The strata in which these remains were found were somewhat higher than those containing the bones of _Orohippus_.

_Measurements._

M. Greatest length of astragalus 0·021 Greatest breadth of ditto ·018 Length of neck of ditto ·005 Width between the condyles ·010 Vertical diameter of face for navicular ·012 Transverse diameter of ditto ·012 Length of calcaneum ·046 Width of face for cuboid ·006

From Henry's Fork.

OROHIPPUS, Marsh.

Am. Jour. Sc. vol iv., p. 207, third series.

_Generic Characteristics._--"The crowns of the upper true molars are composed of a pair of external cusps similar to those of anchitherium. There are two corresponding inner tubercles, from which ridges extend obliquely to the anterior inner margin of the outer cusps; but the anterior ridge is divided so as to form an intermediate anterior tubercle. All the teeth preserved have a distinct basal ridge."

_Species Known._--

Orohippus pumilus, Marsh. Orohippus major, Marsh. Orohippus agilis, Marsh. Orohippus gracilis, Marsh.

Orohippus pumilus? Marsh.

Specimen obtained. Penultimate and third superior molars, with part of zygoma.

From Cottonwood Creek.

Orohippus major? Marsh.

_Femur_ (Plate IX., Fig. 1).--The femur has a small, nearly hemispherical head, developed on a long and slender neck; the head is but slightly out of the axis of the shaft, and has a large pit for ligamentous insertion. The shaft is long, simple, and curved slightly forward. At the proximal end it is broad and flattened axially; below this it becomes expanded fore-and-aft, but it thickens greatly at the distal end, just above the condyles. The great trochanter is large and retroverted, rising above the head, with two prominences rising from it, one on top, the other back. The digital fossa is wide and deep, penetrating far into the great trochanter. The second trochanter is a small rounded ridge; the third trochanter is large and prominent, curving slightly forward. The condyles are long and narrow, projecting very far back, and are separated by a wide and deep popliteal groove. From the external condyle a low ridge runs obliquely, forming the upper border of the shallow popliteal space. The trochleæ are long, very convex, deeply grooved, and symmetrical.

_Measurements of Femur._

M. Width between head and great trochanter ·019 Width at third trochanter ·034 Diameter of head ·019 Width at condyles ·028 Width of trochlea ·015 Height of great trochanter ·015 Diameter fore-and-aft of shaft at middle ·018

The _tibia_ (Plate IX., Fig. 3) is very long and heavy, with broad proximal articular face, the inner borders of which are prolonged upward and separated by a groove.

The shaft at the tuberosity is subtriangular, with strongly concave sides. The tuberosity is prominent, with a deep pit on its upper surface for the insertion of the ligament of the patella. The shaft below becomes sub-cylindrical, and decreases regularly in size downward. Its curvature is forward. The distal articular face is divided by a smooth ridge into two deep facets. The malleolus is long.

The _fibula_ (Plate IX., Fig. 2) is distinct, straight, and very slender. The distal end is but slightly expanded, and is strongly marked by a vertical groove externally. The proximal end articulates with the overhanging portion of the proximal face of the tibia.

_Measurements of Tibia._

TIBIA.

M. Length ·178 Width of proximal surfaces (transverse) ·032 Width of proximal surfaces (antero-posterior) ·019 Transverse diameter of shaft ·022 Antero-posterior diameter of distal articulation ·018 Transverse diameter of distal articulation ·018

_The _tarsus_._--The _astragalus_ (Plate IX., Fig. 5) has the condyles asymmetrical and divided by a deep groove; the head is narrow, with the neck elongate. The face for the cuboid is small, and confined to the external border.

The _calcaneum_ (Plate IX., Fig. 4) is long and compressed, with its upper and lower margins straight and nearly parallel; its tuberosity is large. The face for the cuboid is small.

The _navicular_ (Plate IX., Fig. 6) is proportionately longer and narrower than it is in the modern horse. The internal and middle cuneiforms were probably separate.

_Metatarsals_ (Plate IX., Fig. 7).--Three in number. Are very much shorter proportionately than in the modern horse. In shape they are compressed and arched forward. The distal ends are flattened vertically, arched forward, and deeply grooved in the middle.

The _phalanges_ (Plate IX., Fig. 7) are very short, rather stout, and very smooth and convex above.

The ungual phalanges are very thin and crescent shaped.

_Measurements._

ASTRAGALUS.

M. Greatest width ·029 Greatest length ·022 Length of navicular facet ·017 Width of navicular facet ·012 Length of tibial trochleæ externally ·016

CALCANEUM.

M. Total length ·058 Total width ·019 Depth in front ·022 Length of heel ·035 Depth of heel ·018 Length of cuboid facet ·014

NAVICULAR.

M. Width ·009 Length ·010

PHALANGES.

M. Length of first phalanx ·022 Width of first phalanx ·012 Length of second phalanx ·013 Width of second phalanx ·010 Length of ungual phalanx ·005 Width of ungual phalanx ·010

PALÆOSYOPS, Leidy.

Hayden's Geological Survey of Montana, 1871.--Proceedings Academy Natural Sciences, Philadelphia, 1871, p. 118.--_Limnohyus._--Marsh, American Journal Science and Arts, 1872, p. 124.

_Generic characters._--The dentition is full, I. 3, C. 1, Pm. 4, M. 3; the same in lower jaw. The internal cones of the superior molars isolated from the crescentoid crests. One inner tubercle on the last three premolars. One internal cone on the last superior molar. In lower jaw, true molars with four acute tubercles alternating in pairs and connected by oblique crests. The last molar adds a fifth posterior tubercle. The last premolar lacks the posterior inner tubercle. The canines are in continuity with the incisors.

A broad, triangular forehead. A wide zygoma. Long, projecting nasals. Large temporal fossæ. High sagittal crest. Prominent and nearly vertical occiput.

Palæosyops major, Leidy.

Survey of Wyoming, 1871, p. 359.--_Limnohyus robustus._--Marsh, American Journal Science and Arts, 1872, p. 124.

_Specific characters._--Sagittal crest short and thick. Temporal fossæ not very deep. Frontals diverge rapidly. Occipital condyles wide and low; the same is true of the foramen magnum. Meatus auditorius high and deep. Glenoid cavity shallow; no internal process. As compared with _P. Paludosus_, post-glenoid process not so much compressed. Occipital region comparatively higher and not so concave. The occipital condyles are more prominent. The zygomas are lighter. Head larger than _Paludosus_, perhaps not so large as _Vallidens_.

Description from (i) a head, complete, but distorted, with complete dentition, upper and lower. (2) A head somewhat crushed, and lacking some portions, with full set of upper molars and canines. (3) A great number of fragmentary specimens of different parts of the body.

_Dentition._--In the upper jaw the incisors are arranged in a semi-circle as in _P. paludosus_; they have long fangs and short, conical crowns, with a decided basal ridge, which is very strong in the third. They increase from first to third, which is very large and pointed.

The canines have very large and long fangs (longer than the crowns). The crowns are very stout and pointed, constituting formidable weapons. In section they are nearly circular, with a distinct hinder margin and a slight recurve. A rudimentary anterior margin is sometimes present, and of the faces thus marked off, the inner is much smaller and flatter. The general direction is forwards, downwards, and slightly outwards. There is a diastema of about half an inch between the incisors and canines.

_Premolars._--The first is very small, about half an inch from the canine, simple and conical, with an obscurely marked basal ridge, and two heavy fangs.

Further description of the upper dentition is unnecessary, owing to the complete work of Dr. Leidy upon the subject.

The _lower incisors_ are placed in a semi-circular row, and are somewhat procumbent, though hardly as much so as in the tapir. They are much as in _P. paludosus_, but are relatively smaller, and have not such distinct basal ridges; features which indicate a departure from the carnivorous type, and a nearer approach to the herbivorous type. The lateral incisor, though the largest of the series, is not so large nor so pointed as in _P. paludosus_. There is no diastema.

The _canines_ are about equal in size to those of the upper jaw, growing from stout fangs and permanent pulps. The margins of the crowns are more decided, and are smooth, leaving a very narrow and flat inner face. A feeble basal ridge. When the jaw was closed, the lower canines passed inside and in front of the upper.

The _first premolar_ stands immediately behind the canine, is longer than that of the upper jaw, consisting of a single pointed lobe implanted by one fang, slightly recurved with a flat inner and convex outer face. Passing in front of the first upper premolar, it leaves a considerable diastema between this and the second premolar.

The _mandible_ approximates in form that of the tapir; the lower border is less curved fore and aft, the alveolar border is slightly concave antero-posteriorly. The molars converge in front, presenting a very different arrangement from that in _Sus_. The ramus is heavy, contracting in depth forward, and very slightly in section. Below the alveolus, on the interior side, the ramus is greatly swollen for two thirds of its depth, to accommodate the very long and strong molar fangs.

The rami converge to the second premolar, where they expand laterally to the canine alveolus. The symphysis is shorter relatively than in _P. paludosus_, and the chin is regularly rounded in front. The mental foramen is below the second premolar. The dental foramen is small, very high up, and far behind the molars. The alveolar border ascends rapidly behind the last molar, expanding laterally into two ridges.

The coronoid is slender and recurved. The condyle is broad, flat behind, inclines forward internally; there is scarcely any depression between the condyle and the coronoid. The masseteric fossa is very wide and deep. The angle of the ramus is broken, but evidently has no such posterior extension as in _P. paludosus_. It thins out rapidly behind.

_Measurements._

+---------+---------- | P. pal. | P. major. +---------+---------- UPPER JAW. | M. | M. Length of entire molar series | ·147 | ·170 Length of three true molars | ·085 | ·102 Length of three premolars | ·058 | ·068 Diameter of last molar, transverse | ·039 | ·047 Diameter of last molar, antero-posterior | ·036 | ·036 Diameter of second molar, transverse | ·036 | ·040 Diameter of second molar, antero-posterior | ·033 | ·036 Length of incisor series | ···· | ·075 Fore-and-aft diameter of canine at base | ·016 | ·021 Length of crown of canine | ···· | ·033 Diastema between canines and incisors | ···· | ·013 Diastema between canines and molars | ···· | ·010 --------------------------------------------------+---------+----------

+---------+---------- | P. pal. | P. major. +---------+---------- LOWER JAW. | M. | M. Incisor series | ···· | ·073 Median incisor fang, length | ···· | ·034 Median incisor crown, length | ···· | ·012 Diameter of median incisor crown, transverse | ···· | ·009 Diameter of lateral incisor crown, transverse | ···· | ·011 Diameter of lateral incisor crown, antero-posterior| ···· | ·012 Length of fang of canine | ·055 | ·052 Extreme breadth of fang of canine | ·023 | ·024 Crown of canine, length | ···· | ·034 Crown of canine, fore-and-aft diameter at base | ·019 | ·021 Diameter of first premolar, antero-posterior | ·015 | ·010 Diameter of first premolar, transverse | ·009 | ·007 Diastema between first and second premolars | ···· | ·014 Length of entire molar series | ·164 | ·186 Length of molar series, omitting first premolar | ·132 | ·163 Diameter of last molar, antero-posterior | ·017 | ·050 Diameter of last molar, transverse | ···· | ·027 Depth of jaw below last molar | ·068 | ·075 ---------------------------------------------------+---------+----------