Peterson: Material Discovered in Uinta Basin. 73 



Genus Mesomeryx gen. nov. 



Type: Fragment of maxillary with cheek-teeth in place, C. M. No. 

 31S9. 



Horizon: Uinta Eocene. Lower C. 



Locality: Near eastern border of the Upper Eocene sediments, two 

 miles east of Dragon-Vernal Stage-road, Uinta Basin, Utah. 



Generic Characters: Molars with sharp external convexity of para- 

 and metacones ; the latter tubercles distinctly connected by a fore-and-aft 

 ridge near the external face of the tooth, prominent parastyle, weak meta- 

 style, absence of mesostyle. Protocone formed into an oblique cross- 

 crest on wear. Subselenodont structure of postero-internal tubercle. 

 P- with weak, and P- with strong, deuterocone. 



17. Mesomeryx grangerP^ sp. nov. (Plate XXXVII, Fig. 17). 



General Description of the Type Specimen: The type represents an 

 animal smaller than Bunonieryx elegans Wortman. The dentition 

 has, however, advanced a step further than in the latter genus. This 

 is especially seen in the molar teeth. The protocone is united with 

 the protoconule, so that the two form an oblique forward and outward 

 extended ridge on the surface of a worn tooth as in Hylomeryx. On 

 close examination this ridge is seen to have a slight constriction, but 

 whether or not there was a separation between protocone and pro- 

 toconule, as in the Homacodonts generally, cannot be stated (most 

 likely there was only a solid cross-ridge). There is no postero-internal 

 tubercle on either M- or M-. The present genus appears in this 

 respect to resemble the one just described, but in the present form the 

 para- and metacones are decidedh' less conical and the whole structure 

 of the crown more selenodont. If this postero-internal tubercle (hypo- 

 cone?) had ever existed in this phylum, as for instance in Homacodon, 

 Hylomeryx, Bunomeryx, and Sphenomeryx, it had already been com- 

 pletely crowded out, absorbed, or otherwise replaced by the meta- 

 conule in the Bridger or earlier genera. From what we have just seen 

 in the true Homacodon phylum it would appear to add much strength 

 to Dr. Wortman's views of the process of the development of the 

 quadricuspid selenodont from the quinquicuspid bunodont molar.^^ 

 There is a well-developed cingulum posteriorly on both M- and M-, 



'1 In recognition of Mr. Walter Granger of the American Museum of Natural 

 History, New York. 



^^ Bull. Amer. Mus. Nat. Hist., Vol. X, 1898, p. loi. 



