120 Bulletin Amencan Museum of Natural History. [Vol. X, 



these John Day species are not in the direct line of the tylopodean 

 ancestry.' \ 



Protolabis Cope. 



The next step in the line of cameline ancestry is furnished by 

 the genus Protolabis., originally established upon the greater por- 

 tion of both preniaxillse and maxillne, together with the front of 

 the lower jaw upon one side. This specimen was found near 

 Pawnee Buttes, Colorado, and is from the typical Loup Fork 

 horizon." Another specimen was found by the writer in the so- 

 called Toup Fork Beds of the upper John Day Valley of central 

 Oregon, which was described by Cope as a new species of the 

 same genus. It consists of the anterior portion of the cranium 

 bearing the complete upper dentition in good preservation. 



As regards the type specimen upon which the genus was origi- 

 nally founded, it is necessary to remark that the only distinction 

 between it and Procamelus robustus is to be found in the posses- 

 sion of alveoli for the first and second incisors above, which 

 would indicate a complete superior incisor dentition. In Proca- 

 melus, of the adult stage at least, these incisors are wanting. A 

 careful examination of the specimen shows that the part of the 

 premaxilla in front of the third incisor, upon the right side, is 

 much shorter than that upon the left side, and instead of two 

 alveoli there are in reality three, wh'ch would make altogether 

 four incisors in the premaxilla upon this side. The correspond- 

 ing part of the premaxilla upon the opposite side is much longer, 

 and contains the two alveoli for the first and second incisors. In 

 every other detail the specimen agrees perfectly with Procamelus 

 robustus. Indeed, Cope has pointed out that these first and sec- 

 ond incisors of this series, in all the species of Procamelus., were 



' In this connection it is proper to call attention to the fact that there are important faunal 

 differences between the upper and lower beds of the John Day deposits. These distinctions 

 are so marked as to entitle them to be regarded as separate and distinct divisions of the 

 North American Miocene Be-sides the species of cameloids above described, this upper 

 division contains two species of Merycochwrus among the Oreodonls. J\Icso/up/'iis /irics/ans 

 among the Horses, and Elotlieriuin liuinerosuiii of the Elotheres, which have not been found 

 thus far in the lower division of the beds. There can be little doubt that other important 

 faunal distinctions will be discovered when careful collections are made with this particular 

 object in view. Kor the lower series the name Diceratherium Beds may be retained, but for 

 the upper series 1 herewith propose the name Merycochoerus Beds. 



- Proc. Philad. Acad., 1876, p. 145. 



