1887.] ^♦^J- [Cope 



The direct connection with the f^imilies previously described is not yet 

 known. The indications point to the Oreodontidfc, but no approach to 

 the cervical vertebrae of the Poebrotheriidi3e has yet been found in that 

 family. 



Messrs. Scott and Osborn have described a mammal, from the Bridger 

 Eocene of Wyoming, as a probable member of the camel series, under 

 the name of Ithygrammodoti cameloides. It is only known from two pre- 

 maxillary and a part of one maxillary bones. The former are slender and 

 bear a complete set of incisor teeth, which ai'e followed by a large canine. 

 It is probable that this genus belongs in the camel series, but it cannot 

 yet be positively affirmed. 



Ancestral to the Camelida; is the genus Protolabis Cope, which agrees 

 with Procamelus, the earliest genus of that family in most respects, but 

 differs decidedly in having a full set of superior incisor teeth. In this 

 genus we reach the stage, in tracing back the ancestry of the camels, 

 which we find represented by Oreodon, or the Gelocus in the line of the 

 cattle and deer. It is probable, though not certain, that in Protolabis the 

 metapodial bones are combined into a cannon bone as in the Camelidae. 

 If so it differs materially from its predecessor, the genus Pcebrotherium, 

 and must be regarded as the type of a special family, the Protolabidi- 

 D^. But one genus of this family is known up to the present time. Its 

 remains occur in the Ticholeptus beds of Oregon and the Loup Fork beds 

 of Nebraska and Kansas. 



In the Camelid^ we begin to realize the characters of the latest Artio- 

 dactyla, the ruminants. But they diflfer from the typical forms of these, 

 the Booidea, in three important points of the osteology, viz., in the 

 absence of a canal of the cervical vertebrce which in other Mammalia en- 

 closes the vertebral artery ; the presence of an incisor tooth on each side 

 of the upper jaw ; and thirdly, the incompleteness of the keels of the dis- 

 tal ends of the metapodial bones. This character and that of the presence 

 of incisors, are primitive conditions common to all the early Mammalia. 

 The peculiar cervical vertebrsE constitute a specialization, but whether 

 degenerate or progressive remains to be ascertained. In one respect this 

 line exhibits a high specialization, which is present at the earliest known 

 period of its history. This consists in the reduction of the lateral (ii and 

 v) metapodial bones, so that but two functional toes remain. This condi- 

 tion has been reached by the more typical artiodactyles after a much 

 longer lapse of time, for most of the extinct and recent types display lat- 

 eral digits in a well-developed or rudimentary condition ; in but few of 

 them have they totally disappeared. In another respect the line of the 

 camels attains a higher specialization than that of the typical ruminants, 

 although its beginning is that which is common to the entire suborder. 

 This is in the dentition. The reduction in numbers of teeth shown by 

 Owen to characterize the historical succession of all Mammalia, is carried 

 further in the molar series of camels than in any hoofed order ;- for in the 

 final term or genus, Eschatius (Cope), there is but one premolar left in the 

 upper jaw, and that is reduced to a simple cone. The true molars never 



