MERYCOCHCERUS 159 



P 1 is simple, has an internal cingulum, and in some cases is set somewhat obliquely in the jaw. The 

 remainder of the teeth are more hypsodont than in P r ornery cochcerus. P 4 is more quadrilateral 

 than in that genus and has a small posterointernal cusp. The molars increase rapidly in size, so that 

 the length of M 3 is more than four-fifths of the combined length of M 1 and M 2 . The metastyle of 

 M 3 is robust, and in some specimens the posterior half of the tooth is rotated inward to some extent. 

 The parastyles and mesostyles are rolled forward more than in M. magnus, where they are nearly 

 normal to the outer face of the tooth. 



Inferior: The lower molar-premolar index is 0.72. The incisors are narrow and slender. The 

 true canine is moderately large, and Pi is more robust than the superior canine. P 2 is rotated in the 

 jaw to such an extent that half of the crown is situated internal to the canine and a third is external 

 to P 3 . The premolars are shorter than those of Promerycochcerus, and the molars are more hypso- 

 dont. The latter teeth increase rapidly in length from front to back, so that the length of M 3 is 

 greater than the combined length of M, and M 2 . 



Skeleton: The cervical centra are very short, the seventh being about one-fifth shorter and 

 wider than the corresponding one of Sus and having much larger zygapophysial facets. There is no 

 vertebrarterial foramen. The dorsal centra are large, with stout and long triangular spines. The 

 lumbars are reduced in length. The humerus is short and stout. The ulna and radius are moder- 

 ately short, with the ulna larger than the radius and not much recurved. 



Matthew (1901 A, p. 408) described the fore foot as follows: 



The scaphoid has a narrow facet for the trapezoid and one about twice as wide for the magnum. The 

 fourth and fifth metacarpals are very short and stout, the latter over one fifth shorter but of the same proportionate 

 weight of shaft. 



These animals had small feet, with short metapodials closely bound together and stubby toes. 



The iliac portion of the pelvis is short and wide. The femur is long in proportion to the 

 tibia and the foot, thus resembling in this respect many of the Eocene Mammalia. The shaft is 

 straight, oval in cross section, and with the distal end moderately wide but not so thick anteropos- 

 teriorly as in most of the members of this family. 



Matthew (1901 A, p. 409) in describing the hind leg said: 



The trochlea is short, broad, low, and shallow, the condyles wide apart and not very prominent. The tibia 

 is rather short, straight-shafted, the cnemial crest prominent and extending nearly half-way down on the bone; 

 the external end more quadrate than is usual among oreodonts, from the thickening of the external side; the 

 internal malleolus long, and exceptionally broad anteroposteriorly. The fibula is slender, the proximal end rudi- 

 mentary with no facet for the tibia, the distal end enlarged suddenly anteroposteriorly to about the same width as 

 the internal malleolus; the shaft has in its middle third a prominent crest projecting antero-internally towards the 

 tibia, and is otherwise of oval section, the lesser diameter transverse. The astragalus is like that of Promeryco- 

 chaerus, shorter and more oblique than in any other oreodont. The foot is very much like that of P. montanus, 

 but one seventh smaller, the lateral toes a little less reduced, the second cuneiform united to the third with a less 

 noticeable step on the distal facet, the internal cuneiform narrower and its facet for metatarsal II less distal and 

 more external. The toes are proportionately shorter, and the ungual phalanges reduced to small, almost nodular 

 bones of semicircular outline, flattened and rugose without any trace of the medial ridge seen in other artiodactyls 

 (except the camel). 



Of the skeletons of the young individuals, Matthew (1901 A, p. 41 1) wrote: 



In the outlines of the skull the young resemble other oreodonts much more than does the adult. The short- 

 ness of the cranial region is marked, as in the adult, and the maxillopremaxillary coossification is complete and the 

 nasals much reduced. But the occiput is not nearly so high nor so wide, the mastoid plates are quite moderately 

 developed, the zygomatic arches not nearly so wide nor so deep, and the cellular bony tissue layer on the frontal 

 and cranial region is quite moderate in amount, so that the back of the skull is not exceptionally high, and the 

 temporal crests unite to form a short sagittal crest before reaching the occiput. 



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