646 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



ous series of I. 2 or 3 ; 0. 1, P. M. 3-4; M. 3 ; the canines but moderately 

 developed. 



A comparison with Nasua reveals no distant affinity. As above re- 

 marked, the fore-limb presented a great similarity in this genus and 

 TomitJierium. The teeth, though less numerous, in the molar series have 

 tlie cutting tj^pe anterior and tubercular posterior, in both genera. 

 Notharctus, Leidy, resembles Ifasua still more than does TomitJierium, 

 and occurs in the same Eocene strata. Professor Leidy originally re- 

 garded it as a Carnivore, and subsequently (Hayden's Survey Montana, 

 1871) placed it among UDgulates. He was probably nearly correct on 

 both occasions, and that only a technical line will ultimately decide 

 whether it be not a monkey. 



But the genus which associates more definitely the orders Carnivora 

 and Quadrmnana is the Cercoleptes, which F. Cuvier* placed between 

 the tv7o. Its two cutting premolars and three true molars, with the co- 

 ossified rami of the mandible, are truly Quadrumanous features, although 

 it should on other grounds be regarded as a plantigrade Carnivore. 

 Several of the extinct genera of the Wyoming Eocene will prove to be 

 allied to this form. 



Cercoleptes does not, however, present us with the ultimate original 

 type of the Carnivora. Such a type must also generalize the seals, with 

 their longitudinal, cone-bearing molars, and flat, fissured claws. Some 

 of the seals also unite the scaphoid and lunar bones later in life than 

 other Carnivora ; hence we would reasonably look for the division of 

 these bones in their ]}redecessors. The flat-clawed genera of Wyoming t 

 answer these demands. The genera Mesonyx and Synoplotherium pre- 

 sent us with a series of molar teeth which repeat each other in form, 

 are compressed below, and bear conical cusps. The jaws in the latter 

 genus are slender, and the canines tend to the great development seen 

 in many seals; but priucipally, the scaphoid and lunar bones are dis- 

 tinct, and the claws flat and widely fissured. The tympanic bone is 

 more like that of the bear and some seals, than that of the digitigrade 

 Carnivora. These geuera, though probably good swimmers, were well 

 removed from the seals in the structure of the long bones of the limbs, 

 and were probably remote in their ancestry. 



In Oligotomtcs, Orotherium, HyopsodMS, and similar forms, the conic 

 tubercles have a slight alternation, and the posterior, which has a cres- 

 centoid section in wearing, inclines to connection with both the inner- 

 conic tubercles by low ridges. These ridges are fully developed in 

 Palmosyops, so that we have a dental crest of two Y's in the inferior 

 molars. This, in wearing, produces the two crescents of FalwotJierium. 

 The addition of two tubercles on the inner side takes place in the higher 

 forms, which terminates in the four crescent-bearing molars of the 

 Ruminants. How this is done is best proven by examples from the 

 maxillary teeth. ,? 



In Orotherium vasacciense, there is a tendency for the conic tubercles 

 to be connected in pairs by low cross-ridges. These ridges, fully de- 

 veloped, produce the two cross-crests of Ryrachyus and Tapirus. In 

 Bhinoeerus, the outer portion retains a crescentoid form, giving rise to an 

 L-shaped crest. In Batlimodon diagonal ridges appear, which would 

 result in two V's, as in Falieosyops, were it not that both transverse and 

 oblique elements of the posterior Y disappear, leaving but one such in 



* Deutes des mammifers, p. 31. 



t See the Flat-clawed Carnivora of Wyoming, by E. D. Cope, April, 1873. 



