448 Wortman — Studies of Eocene Mammalia in the 



The specimen is from the lower part of the Bridger Beds, 

 and was found by R. E. Son. 



A larger species, U. vorax, was established by Leidy, from 

 the same 'horizon, upon a fragment of a lower jaw in which the 

 heel of the sectorial and the penultimate molar are preserved. 

 The heel of the sectorial is not so trenchant 

 as in the preceding species, but exhibits a 

 more or less intermediate condition between 

 the basin-shaped and cutting forms. Sub- 

 sequently Scott described another species 

 (Miacis bathygnathus) from the Bridger, in 

 Figure 16. — First which the greater part of the lower jaws 

 superior molar of Uinta- and some few fragments of the skeleton are 

 cyonvorax{?); natural preserved: but it would appear that it is 



size. r , -i. ,- , £ tt mi 



not distinct irom U . vorax. Ihe jaws are 

 short' and deep, the symphyseal region abruptly rounded, and 

 the premolars, as indicated by their alveoli, were not reduced 

 in size below the normal ; the canine, moreover, was more or 

 less laterally compressed at its base. The few skeletal frag- 

 ments exhibit characters of the early dogs. In this connec- 

 tion, I give a figure (figure 16) of a first superior molar, which 

 probably belongs to this species. A third species from the 

 Washakie, TJ. pugnax, displays the same jaw characters as 

 U. vorax, but very little is known of it. A fourth species, 

 U. brevirostris, was described by Cope from the Wind River 

 Beds, and this species has also been identified from fragmen- 

 tary remains from the Wasatch of the Big Horn Valley, 

 clearly showing that the genus is of very ancient origin. 



It now appears, even from this fragmentary evidence, that 

 the direct connection between this group and the genus 

 Daphcenus of the White River Oligocene is so exceedingly 

 probable, that it may be hypothetically assumed, notwithstand- 

 ing the fact that the intermediate stages in the Uinta are as 

 yet to a large extent wanting. The genus from this latter 

 horizon, to which Matthew and myself gave the name Pro- 

 daphcenus, is more probably a member of a line leading to 

 Amphicyon. This is strongly suggested by the fact that the 

 third superior premolar, and presumably the two anterior 

 ones, are considerably reduced in size, a feature that does not 

 occur in any known species of Daphcenus, but does occur and 

 constitutes one of the characteristic peculiarities of the genus 

 Amphicyon. 



The typical species of Uintacyon, V. edax, finds a highly prob- 

 able successor in Daphcenus vetus, in which the heel of the 

 lower sectorial, as well as that of the second molar, are tren- 

 chant, and the lower jaw is slender and elongate, with marked 

 traces of the characteristic abruptness of the mental region so 



