1898.] Wortman, Extinct Camelidm of North America. 1 03 



phyla of the Selenodonts, but it appears to me certain that the 

 hypothesis herein advanced is the correct one for the formation 

 of the tetraselenodont superior molars of the Cameloids, Pecora, 

 Tragulines, and probably the Oreodonts and Anthracotheres. 



Parameryx (Leptotragulus) proavus S. &^ O. 



This genus was first described by Marsh' and later by Scott 

 and Osborn,'* who considered that it to belongs to the Traguline 

 division of the order. Later Scott gave a fuller account of it^ 

 and placed it in the Tylopoda"* immediately ancestral to Pocbro- 

 therium of the White River Oligocene. The materials in the 

 Museum Collection do not add very materially to the knowledge 

 of this form ; however, there are some important points to be 

 made out from it. There are four specimens which I refer to this 

 species, the most important of which are a fragmentary skeleton 

 containing a fairly good hind foot, together with the posterior 

 part of the last lower molar (No. 2509). The other specimens 

 pertain exclusively to the lower jaw (Nos. 1803, 1805 and 1808). 



In the lower jaw there is one diagnostic character by means of 

 which the last lower molar can be recognized, and that is the 

 presence of an extra cusp upon the inner border of the heel near 

 its point of junction with the postero-internal cusp. It is by 

 means of this character alone that I associate the fragmentary 

 skeleton with this species. The lower molars are of the typical 

 selenodont pattern, and the cusps more elongated than in any of 

 the cotemporary Selenodonts. 



The inferior premolars are three in number, the fourth being pro- 

 vided with a well-developed internal cusp and heel. The second 

 and third are simple and without accessory tubercles. In advance 

 of the second premolar there is a considerable diastema, in front 

 of which is the large procumbent alveolus for the canine. The 

 incisors are not preserved, and this region of the jaw is so much 

 broken as not to reveal their alveoli. 



1 ' Introduction and Succession of Vertebrate Life in America,' 1877. 



2 ' Preliminary Report on the Vertebrate Fossils of the Uinta Formation,' Proc. Am. Philos. 

 Soc, 1877, pp. 255, 264. 



3 'Mammalia of the Uinta Formation,' Trans. Am. Philos. Soc, N. S., Vol. XVI, Part iii, 

 Aug. 20, 1S96, pp. 479-486. 



■* Marsh had, however, clearly recognized the affinities of this genus with the Tylopoda ten 

 years previously, since we find in the address above quoted the following statement : " A most 

 interesting line, that leading to the Camels and Llamas, separates from the primitive seleno- 

 dont branch in the Eocene, probably through the genus Parameryx. 



