472 Annals of the Carnegie Museum. 



and neck, second superior premolar reduced, hypsodont dentition, 

 and the metacarpals entirely separated ; while Oxydactylus has the 

 cervical region and limbs greatly elongated, no reduction in the den- 

 tition, brachydont teeth, metacarpals entirely separate and the meta- 

 tarsals coosified only by their palmar processes. Alticamelus differs 

 from Oxydactylus in its much greater size, by having the first and 

 second incisors absent and the metapodials united. In Protomoyx 

 (^Goinphotheriiii)i~) the limbs are comparatively much shorter than in 

 Oxydactylus, the orbit is rounder and more anterior in position, the 

 angle on the lower jaw is longer, and the metapodials are separated. 



After a careful study of all the material at hand it is believed by the 

 writer that Oxydactylus is most nearly allied to Protomeryx (^Gompho- 

 therium) from the John Day formation and that some form similar to 

 Alticamelus'^''" in the Pleistocene is the termination of this phylum. 

 While the characters in the dentition of the latter genus, are little 

 changed from those in Frotoine/yx, the orbit is more oblong in shape 

 and more posterior in position. The region between the alveolar 

 border and condyles of the skull is also comparatively shorter. The 

 greatly elongated limbs especially in O. lougipes contrasts strikingly 

 with the rather short limbs in Protomeryx. 



Alticamelus altus""'^ retains some important characters similar to those 

 in O. lo/igipes, although it is much larger and more modified than the 

 latter. The small cranium, and the structure of the neck, limbs and 

 phalanges are suggestive of O. loiigipes. 



In the Pleistocene formation are remains of camels with greatly 

 elongated limbs" and these may represent the termination of this line 

 of American fossil cameloids. This phylum appears to be divergent 

 from that of the true camels and we are at present able to trace it 

 with some certainty to the genus Protomeryx of the upper Oligocene. 

 Oxydactylus presents characters resembling both the recent camels and 

 other Loup Fork genera, but some of these are doubtless due to paral- 

 lelism in development and do not signify relationship. In O. loiigipes 

 we seem to have an animal which in some respects is even more spe- 

 cialized than the recent Camelida^ while in other respects it is more 

 primitive. The elongated cervical region with the comparatively 

 longer limbs, the metacarpals being 15 mm. and metatarsal 8 mm. 



'^'^ Memoirs Am. Mus. Nat. Hist., Vol. I, Part VII, page 422, 1901. 

 '^^ Memoirs Am. Mus. Nat. Hist., Vol. I, Part VII, p. 430, 1901. 

 ^* Memoits Am. Mus. Nat. Hist., Vol. X, p. 132, 1898. 



