436 Annals of the Carnegie Museum. 



than the third and fourth and is fixed by two strong roots. Pm. ^ is 

 very similar to pm. -^, but has a much stronger internal basal cingulum 

 and has a deep, narrow median valley, which is subject to consider- 

 able variation in different individuals. Pm. i differs from the others 

 by having the internal crescent complete, and the anterior and poste- 

 rior depressions of the external surface not so deep as in pm. -2. and ^. 

 On the antero-external face of pm. A there is a prominent rib re- 

 sembling the corresponding rib on pm. A in the recent camel and 

 llama. 



In O. longipes premolars -, ^ and i have undergone no reduction in 

 size and little modification in form and resemble those of Poebrotherium 

 and Protomeryx."' 



The molars are brachyodont and closely resemble those of Pro- 

 tomeryx. The first is nearly one third longer antero-posteriorly 

 than pm. i. The succeeding teeth increase rapidly in length, 

 the last molar being the longest by 2 or 3 mm. In width, the first 

 molar differs from that in the recent camel and the llama. The latter 

 genera, especially the llama, have the first molar the widest with a 

 gradual decrease to the posterior portion of the last molar. In 

 Oxydactylus the second molar is the widest while the first is the 

 narrowest in the molar series. The ridges on the external face of the 

 molars are quite prominent especially on the last tooth. This character 

 is subject to individual variation. On molar ^ there are no basal pillars 

 such as are found in the recent camel. The molar teeth in the pres- 

 ent species are narrow and long, differing in this respect from another 

 species of Oxydactylus which will be described later in this paper. 



Inferior Dentition. — (PI. IV, Fig. 4.) The similarity of the 

 superior incisors to those of Poebrotherium is repeated in the inferior 

 series. Taken as a whole, the inferior incisors are rather small in 

 comparison with those of the llama, the median pair being the small- 

 est. The incisors are placed nearly as close together as they are in 

 recent genera, and are well adapted for cropping grass.* As stated 

 above, the superior incisors are separated by short spaces ; they are 

 comparatively small and seem ill adapted for their required function 

 in feeding. It would seem that there were cartilaginous pads on the 

 premaxillaries which assisted to some extent at least in this operation. 

 The canine is very unlike that of Poebrotherium. The latter has the 

 canine greatly compressed laterally, the antero-posterior diameter be- 



'^ Memoirs Am. Mas. Nat. Hist., Vol. I, Part VII, p. 422, 1901. 



