Peterson: Material Discovered in Uinta Basin. 75 



the Hypcrtragulids, the Camelids, the Oreodonts, and other Artio- 

 dactyls must also be admitted. In my judgment these Uinta genera 

 as well as Ilomacodon constitute a sub-family distinct from the Dicho- 

 bunids of Europe.^^ They represent an American branch, whose com- 

 mon ancestors, no doubt, also gave rise to those of Europe. Upon 

 the whole the details of structure in the dentition differ considerably 

 in the genera representing the two regions. This is especially notice- 

 able when such European genera as Mouillacitherium and Metrio- 

 therium^'^ are compared with the Uinta forms. The protocone sends a 

 spur backwards, which has a tendency to close the cross-valley in the 

 European genera, while the valley is clear in the American genera, 

 analogous to what is seen in Oxacron and Ccenotheriuni of Europe. 

 The hypocone of the European genera appears to have a greater 

 functional value, that is: it is of proportionally larger development 

 and apparently expresses a greater degree of permanency, which is 

 especially emphasized in the Oxacron-Ccenotherium phylum. These 

 phyla are, however, not recognized by Stehlin, and others, as having 

 any especial relation to the true dichobunids. 



If we regard the Homacodon-Hylomeryx-Btaiomeryx-Sphenomeryx 

 and the Mesomeryx phyla as at all closely related, we have clearly a 

 tendency toward the quadricuspid condition in the American forms. 

 In Dichohune according to Stehlin's reconstruction {I.e., p. 604; 607) 

 we have a skull proportionally longer, lower, and narrower, with the 

 premaxillaries heavy, in order to support the large incisors. The upper 

 canine has specialized in size and shape, so that it differs much from 

 that in Homacodon and Hylomeryx. 



So far as I am aware, the HomacodontincB are not represented in the 

 Oligocene or later epochs of North America. Dr. Sinclair's opinion 

 {I.e., pp. 294-295), that several divergent lines of the bunodont Artio- 

 dactyls are already established in the lower and middle Eocene of 

 North America is altogether quite likely. It is also probable that 

 some of the lower Eocene genera, already partially known, may prove 

 to be in the line of the HomacodontincB. 



33 From our present knowledge of Bunophorus (Bull. Amer. Mus. Nat. Hist., 

 Vol. XXXIII, 1914, p. 273) it is perhaps premature to here include this Wasatch 

 genus, which may, however, be a forerunner of Homacodon ,as Dr. Sinclair suggests. 



34 Stehlin, G. H., Abhand. Schweiz. Paleont. Gesellsohaft, Vol. XXXIII, 1906. 

 pp. 628, 661. 



