TRANSACTIONS OF WAGNER 



UINTA SELENODONTS 



A. Upper Jazv. (Plate III., figs. 20-23; Plate IV., fig. 25.) The incisors 

 are rather small, antero-posteriorly compressed, and chisel-shaped. These 

 teeth would seem to vary in number; in some specimens, at least of P. parvus, 

 three are present, while in P. {Agriotherimn) paradoxiais only one or two are 

 found. Wortman says on this subject : " In all of our material I have not yet 

 seen a specimen among the oreodonts other than Lcptoreodon that has a full 

 set of incisors in the upper jaw. Marsh figures the type of Eomcryx pumilus 

 with but two superior incisors, and if Protoreodon has the full complement, as 

 believed by Scott, then the two genera are certainly distinct. In two speci- 

 mens in the Museum collection which correspond closely with Protoreodon 

 parvus, as described by Scott, there is but a single incisor on each side above, 

 and the premaxilla- are widely separated from each other in the median line." 

 ('98, p. 96, foot-note.) Ordinarily such a difference in the number of the 

 incisors and in the form of the premaxillaries would certainly be sufficient 

 ground for a generic distinction, but in the present instance, as in the titano- 

 theres, the variability is so great that for the present at least it seems better to 

 include them all under one term, with the exception of Hyomeryx, which 

 seems to be distinct. The canine is of the characteristic oreodont form, with 

 D-shaped transverse section and abraded upon the posterior face. It is, how- 

 ever, relatively a little more slender, elongate, and recurved than in the later 

 representatives of the family. 



A very short diastema succeeds the canine, but only sufficient to provide' 

 for the caniniform py, which of course bites behind the upper canine. The 

 premolars are of thoroughly oreodont type, but are somewhat simpler, more 

 compressed, and more trenchant than those of the White River genus, though 

 in the structure of these teeth there is considerable specific and individual varia- 

 tion. The first and second premolars are each carried upon two fangs and 

 have simple, compressed, and trenchant crowns, which, when seen from the 

 outer side, have the cordate profile characteristic of the family; p^ differs from 

 pi in the presence of a better developed internal cingulum. P^ is always im- 

 planted by three roots and is wider transversely than p-^-, but the development 

 of the inner side of the crown varies greatly. In P. paradoxiais (Plate IV., 

 fig. 25) there is only a feebly marked internal cingulum ; in P. minor (Plate 

 III., fig. 23) the cingulum is quite distinct and a small deuterocone makes its 

 appearance, while P. pai"vus (Plate III., fig. 20) and P. pumilus display an in- 

 creasing size of this element. In the latter species Marsh figures the deutero- 

 cone as being almost as large and as completely crescentic as on p^. ('94, p. 



