﻿BOYSEN RESERVOIR VERTEBRATE FOSSILS WHITE 197 



HYOPSODUS WORTMANl Osborn 



U.S.N.M. Nos. 18453, 18454, two specimens, one -with \ipper and 

 lower molars associated (loc. No. 48FR78) ; U.S.N.M. Nos. 18455- 

 J8460, six specimens, includin«r one maxilla with INI'^^ (loc. No. 

 48FR80). 



There appears to be some confusion in the literature concerning 

 the size lange of the lower molars of this species. Osborn (1002, 

 p. 185) in the original description gives the size range from 11 to 13 

 millimeters. Loomis (1905, p. 422) found that his material exhibited 

 a uniform measurement of 12 mm. Matthew (1015b, ]). 317), in his 

 key to the species of the genus, gives the length of the lower molars 

 as 10 mm. In the material from the Boysen Reservoir area, the two 

 specimens with j\r,_3 have a molar length of 13 mm. In all the speci- 

 mens the length of jN[2-3 varies between 8.0 and 0,0 mm. Van Houten 

 (1045, p. 425) pointed out that most of the Lower Eocene genera 

 could be revised profitably. This is certainly true of Uyopsodus. 



Ilyopsodii^ wortmani has never been adequately characterized in the 

 literature, and if this material is correctly referred, the lower dentition 

 may be characterized as follows: P.j submolariform, anterointernal 

 style well developed and joined to the protoconid by a distinct crest; 

 deuteroconid well developed; anterointernal style, protoconid, and 

 deuteroconid forming a distinct trigonid; heel well developed and 

 trenchant, hypoconid centrally placed and prominent, entoconid small 

 and indistinct from posterior cingulum; Mi with metaconid distinctly 

 twinned, crescents on protoconid well developed, hyopoconulid and 

 entoconid distinct, anterior and posterior cingula present; Ma similar 

 to Ml except that metaconid is indistinctly twinned ; M3 long and nar- 

 row, narrowing rapidly from in front posteriorly, hypoconulid as 

 large as, or larger than, hj^poconid and forming a distinct heel ; 

 entoconid small but distinct, metaconid may or may not be indistinctly 

 twinned. 



This material is not readily distinguishable fromZT. puulus Leidy, of 

 the Lower Bridger, by size, but the teeth of the type are so badly worn 

 that their characters cannot be properly evaluated. 



Order PANTODONTA 

 Family CORYPHODONTIDAE 



Genus CORYPHODON Dumeril and Bibron 



CORYPHODON sp. 



Right P^-* (loc. No. 48FR65). 



This material is inadequate for more than generic identification. 



