Part 3

Among other specimens obtained at the divide between Henry's Fork and Cottonwood Creek, was a nearly complete but somewhat shattered skeleton of a _Palæosyops major_, found contiguous to the head of the same, parts of which are just described. Portions of these are figured on a one fourth scale in Plate II. The description is from a nearly perfect atlas and axis, several cervical, dorsal, and lumbar vertebræ, more or less complete, and a portion of the sacrum and pelvis, in addition to several bones of the limbs.

The _atlas_ has a broad inferior arch, contracted antero-posteriorly, and deeply notched for the prominent odontoid of the axis. The heavy superior arch, inclosing a large and depressed neural canal, is capped by a low tuberosity. It slopes into a flat, and very broad transverse process, which thickens backwards, and is perforated by the vertebraterial canal. Forwards the transverse process is notched for the exit of the first spinal nerve. The anterior or condylar faces are continuous, deeply concave from above downwards; and slightly so from side to side; while the posterior faces are oval, nearly flat, and directed backwards and inwards.

The _axis_ is proportionately small, with a long opisthocœlous centrum, depressed, and produced forwards into a stout conical odontoid process, and marked below by a strong hypapophysial keel, which, developed on the latter half, thickens backwards. The wide and thin pedicles inclose a high neural canal, support the posterior zygapophyses and a prominent and peculiar neural spine. The latter is flattened, broad, and recurved posteriorly, thinning rapidly forwards into a prow-shaped recurved edge. The transverse processes arising from the latter half of the centrum are undersized and widely perforated at base. The anterior faces are very broad, directed outwards, and slightly rounded from above downwards; they expand as they diverge (see Fig. 2). The post-zygapophyses are small convex faces, projecting at the base of the neural spine.

The _remaining cervicals_, five in number, are short, all carinate, except the seventh, and opisthocœlous; with the faces expanding only slightly beyond the body of the centrum. A peculiar feature is a small pit upon the convex anterior face, indicating either a ligamentous attachment with the antecedent vertebra, or a remnant of the notochord. This is a feature we have not noticed elsewhere. A long and heavy transverse process supports a large and widely-perforated inferior lamella. The pedicles are quite wide at base, inclosing a large neural canal. The entire upper part of the arch is unfortunately wanting.

The dorsal centra are smaller than the cervical, slightly opisthocœlous, and carinate. They are sub-cylindrical anteriorly, with decided costal surfaces before and behind; approaching the lumbar region they become subtriangular. A high neural arch supports a stout, but never very high neural spine; this projects backwards, keeled in front, expanding and deeply grooved behind. The zygapophyses are small and nearly vertical. There is a short and thick transverse process.

The _lumbar_ vertebræ are long, decidedly opisthocœlous, becoming wider and more depressed as they approach the sacrum. The first _sacral_ vertebra presents the same characteristics as the last lumbar, only the body of the centrum is slightly shorter. It has a very broad pleuropophysial plate. The remaining sacral vertebræ are broad, and very greatly depressed, rapidly decreasing in size. The transverse processes are slender. The very low neural spines anchylose into a long ridge. The number cannot be ascertained, owing to the fragmentary state of the sacrum. The caudals indicate a tail of not very great length; as the neural canal is small and persists in only a few of the anterior vertebræ.

_Measurements of Vertebræ._ _Pal, major._

M. Atlas, width, including transverse processes ·195 Atlas, length of inferior arch ·082 Atlas, height, including superior and inferior arches ·078 Axis, width, anterior articular faces ·110 Axis, length, excluding odontoid process ·058 Axis, height of neural spine ·096 Axis, length of odontoid process ·025 Seventh cervical, length of centrum ·037 Seventh cervical, width of posterior face ·043 Dorsals, anterior region, length ·038 Dorsals, anterior region, width, articular face ·034 Lumbar, width of posterior face ·058 Lumbar, length of centrum ·056 First sacral, width of anterior face ·059

The ribs, of which great quantities of fragments remain, were slender and not of very great width.

The _femur_, which is figured in Plate I., has a small head, supported by a short neck. The shaft, very broad below the head, supports the third trochanter one third of the way down; below which it takes a cylindrical form, and expands slightly above the trochlea. The two condyles, separated by a wide and deep popliteal groove, are nearly subequal in size--the internal somewhat the larger, while the trochlea is long, narrow, and symmetrical. The great trochanter rises slightly above the head, and overhangs a long and quite deep digital fossa. The second trochanter is small. The popliteal space is slightly concave.

_Tibia._--The proximal end of the tibia is very large, with massive rugosities for muscular attachment. The two proximal faces are subequal, slightly convex, and separated by a prominent spine, which is grooved at the top. The shaft is long, straight, and compressed antero-posteriorly; the anterior ridge on upper third is very high, and expands into the tuberosity, which is enormous; while on the posterior face is a deep fossa just below the head. The distal end of the shaft is remarkably small, with two concave faces--the internal the smallest--with a low oblique ridge dividing them. There is a prominent malleolus.

The fibula (which is a distinct bone) has a small proximal end, and expands slightly below, with a large external malleolus.

_Measurements of Limbs._

M. Femur, total length .420 Femur, transverse diameter at distal end ·098 Tibia, length ·310 Tibia, transverse diameter, proximal articular face ·090 Tibia, transverse diameter, distal articular face ·077

The _pelvis_ is described from the right and left ilia, which are broken as they expand towards the crest; the acetabulum is fragmentary, but all the parts remain. The ischium and pubis are only represented by fragments. As figured in Plate V., the acetabulum is restored from a somewhat smaller specimen. The most striking feature of the _ilium_ is the long and somewhat constricted neck. The acetabular border is long and curved forward, thinning gradually as it approaches the crest; and marked on the iliac surface, near the acetabulum, by a slight rugosity for the rectus muscle.

The ischial border, while less arched, is probably longer; and the sacral surface, distinctly defined, indicates that the rounded upper border of the ilium rarely reached above the sacral spines. There is a deep groove between the ischial and pubic borders, the latter disappearing about half way up the iliac surface. The gluteal surface near the acetabulum is much depressed; above it expands into a broad, flat, thin plate.

The _ischium_ has a stout neck and thick expansion below; the upper border is very heavy. From what remains of the _ischium_ and _pubis_ we can infer a large elliptical obturator foramen, a short pubic symphysis, a narrow and rather slight pubis, with a small nearly cylindrical neck. The acetabulum is deep, with a thick well-raised border, and a large, oblong, and very deep pit for the ligamentum teres.

_Measurements of Pelvis._

M. Ilium, transverse diameter above acetabulum ·062 Ilium, long diameter (estimated) ·232 Acetabulum, greatest diameter ·050 Ischium, transverse diameter below acetabulum ·041 Pubis, diameter at obturator foramen ·035

The _tarsus_ is arranged in the usual Perissodactyle order. The _calcaneum_ is stout, of good length, tuberous, but not expanding much at the extremity; presenting two faces for the astragalus, of which the internal is the largest, and a large distal face for the cuboid. The _astragalus_ is wide, with less asymmetry in the two articular facets than is common. It articulates with both the cuboid and navicular.

_Measurements of Tarsus._

M. Astragalus, total width, tibial facets ·048 Astragalus, total length ·056 Astragalus, length, navicular facet ·046 Astragalus, width, navicular facet ·035 Calcaneum, total length ·120 Calcaneum, total breadth ·057 Calcaneum, length of tuber calcis ·050

All the above were found at Henry's Fork Divide. In another locality, in connection with a fine head of _P. major_, was found the lower half of a _humerus_.

The _shaft_ is cylindrical and twisted, expanding widely at the distal end. Of the two condyles the external is the largest; and, to quote from Dr. Leidy, "a deep supra-condylar fossa occupies the front of the humerus, opposed by a deeper and more capacious anconeal fossa." The greatest breadth between the supracondyloid eminences is ·091 m.

Palæosyops paludosus, Leidy.

Cont. to Ext. Vert. Faun, _P. lævidens_ Cope. U. S. Geol. Survey of Terrs, 1872, p. 591.

_Specific characters._--Second superior molar has but one outer tubercle. The cones are low as compared with _P. major_. The cingula are much less developed. The angle of the lower ramus is much longer. The zygoma is massive and wide. An internal process on the glenoid cavity. Temporal fossæ very deep. Crest of occiput nearly in same vertical line as occipital condyles.

The full details of _P. paludosus_, which follow, may seem somewhat unnecessary, to one familiar with the comprehensive work of Dr. Leidy upon the subject. Care has been taken not to retrace any of his steps; and the descriptions given below are of those parts of the animal which he did not possess at the time of writing. They include (1) a cranium perfect posterior to the orbits; (2) a right _ramus_ mandibuli, with full dentition, except the first premolar; (3) portions of the fore-limbs, scapula, and pelvis, pes and manus, and many fragments of other parts.

Among the first discoveries on Cottonwood Creek, in a stratum of fine green sand, was a head of _P. paludosus_, complete posteriorly, and broken off just behind the orbit. A rear view of this has been admirably figured in Plate I.

_General appearance._--The base of the cranium is of great width; the occiput is high, inclined very slightly backwards, and deeply concave from side to side. The forehead is triangular and narrow. The temporal fossa is of immense size and depth, leaving a small intracranial cavity. The zygomas are heavy, and arching widely outwards give this part of the head a strong resemblance to the _Felidæ_.

_Description in detail._--The narrow but prominent _basioccipital_ segment is broadest posteriorly and tapers forwards; divided by a median ridge, which expands anteriorly into a large tuberosity; a feature also characteristic of the tapir. About half an inch in advance of the condyles are the condylar foramina. The _condyles_ are formed of the exoccipitals, which are low and of great lateral expansion. Their junction with the mastoids is marked by a large foramen. The _par-occipitals_ are short and styliform. The _supra-occipital_ region is very large, high, and deeply concave from side to side, much wider than in the tapir, with a marked interparietal suture. The _condyles_ are wide, but not very deep, approaching each other very closely below. The _basisphenoids_ are long and narrow, tapering forwards. The _alisphenoids_ are mutilated, but indicate large vertical ridges joining the parietals, and heavy pterygoid processes, perforated at the base by the alisphenoid canal. They are again perforated by the foramen ovale three fourths of an inch behind this. This completes the base of the skull.

The _parietals_ are very large, they form nearly the whole of the temporal fossil; which, deep and wide, enclosing a small cranial cavity, contrast strongly with the long and shallow temporal fossæ of the tapir. The parietal crest is very broad, and grooved at the top. This high crest and deep adjacent temporal fossæ we at first mistook as pointing to an exclusively carnivorous type. The forehead has a triangular appearance, from the divergence of the two side ridges of the sagittal crest. The _postorbital_ processes are very large, but do not reach the opposing processes of the _malar_. The orbit is thus left incomplete posteriorly, while in form it greatly resembles that of the _Sus_. The _squamosal_ encroaches considerably upon the temporal; and sends outwards and downwards a great zygomatic process, which arches outwards from the skull as in the _Felidæ_, and is more powerful than in any living carnivore (Leidy.) A strong downward direction is especially characteristic, the whole describing a sigmoid curve. The _mastoids_ are of great size vertically, and transversely they are confluent with the par-occipitals. A low, thick process on the internal side of the glenoid cavity prevents lateral motion.

The _nasals_ are long, broad, and thick, convex from side to side, narrowing slightly anteriorly. They are straight, as in _Sus_, which they resemble more than they do either tapir or rhinoceros. The anterior borders are rounded, and do not reach as far forward as the symphysis of the premaxillary. The _malar_ is broad and thick, probably forming but little of the face, being directed downwards and backwards to meet the zygoma. The postorbital process is short, and rather larger than Dr. Leidy has indicated. The _maxillaries_, smaller proportionately than in _Sus_, form posteriorly the floor of the orbit; while the infraorbital foramen is situated over the last premolar. The premaxillaries fail to reach the nasals.

_Comparative Measurements of Head._

+----------+---------+------- | P. | P. | |paludosus.| major. | Tapir. ----------------------------------------+----------+---------+------- | M. | M. | M. Height of occiput | ·122 | ·148 | ·120 Breadth of occiput at post tympanic | | | processes | ·160 | ·166 | ·110 Breadth of cranium at ends of | | | post-glenoid processes | ·172 | ·210 | ·126 Transverse diameter of occipital foramen| ·031 | ·049 | ·040 Vertical diameter of occipital foramen | ·027 | ·033 | ·027 Depth of occipital condyles | ·033 | ·039 | ·029 Breadth of occipital condyles | ·040 | ·049 | ·041 Breadth at occipital condyles together | ·082 | ·100 | ·082 Width of basioccipital at anterior | | | condyloid foramina | ·038 | ·039 | ·028 Width of basioccipital at junction with | | | basisphenoid | ·025 | ·032 | ·020 Width of crest dividing the temporal | | | fossæ posteriorly | ·011 | ·020 | ·011 Breadth of cranium outside of zygomata | ·262 | ·280 | ·180 Depth of zygoma | ·046 | ···· | ·036 ----------------------------------------+----------+---------+-------

_Lower jaw_ of _P. paludosus_ described from another specimen.

The peculiar feature of this jaw is its remarkable extension back of the molar series (a feature which has not been noticed heretofore), the distance from the last tooth to the angle being greater than the length of the entire molar series. From beneath the last molar, the lower margin curves gently up to the symphysis. The alveolar border is but slightly curved. Behind the last molar the lower margin forms a sigmoid curve, much more decided than in _P. major_ (first upwards and then downwards), and the ramus thins out rapidly to the angle, where it has a slightly raised border; at the diastema the ramus curves outwards so as to throw the canines out of the line of the molars. The symphysis is long.

_Dentition._--The incisors, three in number, from length and shape indicate a semi-circular arrangement, as in most Perissodactyles. They increase from first to third. The crown of the first resembles very much that of the ruminants, but has a straight posterior basal ridge. Its forward edge is worn so as to expose a small tract of dentine. The second is larger, but very much like the first in conformation; while the third has an acute conical crown with a strong basal ridge.

Of the _premolars_ the first is wanting in this specimen. The second is bilobed, the anterior lobe much the larger. It has a small accessory tubercle on its anterior slope. The outer face is rounded, the inner nearly flat. The posterior lobe is very small and obtuse, and with the inner face slightly grooved. In third and fourth the valley between the lobes and the groove on their faces enlarge; while the anterior lobe becomes relatively smaller.

_Measurements of Lower Jaw._

M. Diastema between canine and first premolar ·024 Length of entire molar series ·143 Distance between last molar and extremity of angle ·147 Depth of jaw at last molar ·070

Among the first discoveries on Cottonwood Creek, in connection with the lower jaw of _P. paludosus_ just described, were an ulna and radius, and part of the manus and scapula of the same. These have been figured, together with other fragments belonging to the same species, in Plate III., and form an interesting complement to the nearly complete hind limb of _P. major_ previously described.

The _scapula_ has a shallow oval glenoid cavity, which is concave longitudinally. Separated from it by a narrow notch is a strongly recurved coracoid, placed on the inner side of the bone. Above the coracoid the border is thin, and arches inwards and then forwards; while the glenoid border is much straighter, rising from a slight tuberosity. The spine rises gradually from the glenoid, and does not bear any indication of an acromion.

The _humerus_ is represented by proximal and distal extremities. The latter presents the same characters on a smaller scale as in _P. major_. Upon the proximal end there is a deep bicipital groove. The greater tuberosity has a hooked anterior projection, and runs back into a ridge behind. (See Fig 7, Plate III.)

The proximal end of the _ulna_ (of median breadth anteriorly) narrows into a prominent ridge behind. This gives a trihedral character to the shaft. This is persistent, but is less marked as the fore-and-aft diameter decreases. The remaining features of note are a high tuberous olecranon expanding behind; a shallow sigmoid, divided by a deep fossa into two long divergent articular faces; a trihedral shaft tapering slightly, but distinct from the radius; a narrow distal extremity, with a small irregular face for the cuneiform.

The _radius_ has a rather short shaft, curved forwards, expanding below, and placed immediately in front of the ulna. A strong ridge runs from the external tuberosity up the posterior face of the shaft, disappearing two inches from the top. The proximal end, fitting against the ulna by two small faces, forms the greater part of the elbow-joint, a strong median ridge dividing the proximal face into two subequal surfaces with well-raised borders. The distal end of the shaft is rugose, and more prominent than the proximal. It has an oblong transverse face, which is slightly concave fore and aft. The position of the radius, immediately in front of the ulna, and its manner of articulation, remove any possibility of rotation, a feature in strong contrast with what we should expect from the character of the head.

_Measurements of Ulna and Radius._

M. Ulna, length, excluding olecranon ·224 Ulna, length of olecranon ·080 Ulna, transverse diameter, proximal surfaces ·041 Ulna, diameter of shaft at median line ·038 Ulna, fore-and-aft diameter, distal face ·025 Ulna, transverse diameter, distal face ·017 Radius, proximal face, transverse ·048 Radius, proximal lace, fore-and-aft ·030 Radius, median diameter, shaft ·019 Radius, median diameter distal face, transverse ·043 Radius, median diameter distal face, fore-and-aft ·016

The _manus_ is described from the third and fourth metatarsals, with three phalanges. The metatarsals are short, with a wide, stout shaft, flat in front and slightly arched forwards behind. The proximal ends unite and form a continuous articular face, concave from side to side; while upon the exposed sides are smooth facets, indicating the presence of two additional toes of less size. (See Plate III.) The convex distal faces are marked behind by a slight groove.

The _phalanges_ are very short and broad, the lower facets marked by a shallow median groove. The ungual phalanx is wide and short, with a crescentic outline.

_Measurements._

M. Third metatarsal, total length ·090 Third metatarsal, transverse diameter, proximal face ·017 Third metatarsal, transverse diameter, distal end ·019 Second phalanx, length ·024 Third phalanx ·014 Total estimated length of manus (6 inches) ·155

Palæosyops vallidens, Cope.

Proceedings Am. Phil. Society, 1872, p. 487; Hayden's Survey, 1872, p. 572.

_Specific characters._--Founded on details of dental structure. Superior size. In the upper molars two strong transverse ridges connect the inner tubercle with the outer crescents, inclosing a pit between them. In the premolars the outer crescents fuse almost into a single ridge. These united crescents are relatively narrower. The inner molars are also narrower, and the posterior tubercle of the last is an elevated cone.

Fragment of a lower jaw containing the two posterior molars. The measurements of the teeth are identical with those given by Professor Cope. The depth of the ramus below the last molar is three and one third inches, and it is slightly heavier below than in _P. major_.

_Restoration of Palæosyops._--The elevation of _Palæosyops major_, which is taken as a type, was approximately the same as that of _Palæotherium magnum_ as restored by Cuvier.

The nearly complete ilium, femur, tibia, and tarsus of _P. major_ in our possession, enable us to make the following estimate of the elevation of the hind quarters.

INCHES.

_Pelvis_, height of ilium above acetabulum 9 _Femur_ and _tibia_ by actual measurement, allowing for bend at the knee 26 _Tarsus_, from astragalus, and cuboid 3 _Metatarsus_ and _phalanges_ (estimated from manus of _P. paludosus_) 8 -- 46