848 THE WHITE El VEE FAUNA. 



MYOMOKPHA. 

 EUMYS (Leidy non>) Cope. 



Annual Report of the U. S. Geological Survey of the Territories, F. V. Hayden in charge, 1873 (1874)^ 

 p. 474. — Eumys Leidy (name only), Procee<ling8 Academy, Philada., 1856, p. 90; loc. civ. 1857^ 

 p. 89; Extinct Mamm., Dakota and Nebiiitka, p. 342. 



1 n o 



Dental formula: I. ; C. ; M. -. Crowns of the superior molars sup- 



porting two external cones, and two internal tubercles of crescentic section 

 which communicate with the former by .transverse ridges. Inferior molars^ 

 of similar constitution, but reversed, the conic tubercles being interior and 

 the crescentic exterior. The posterior tubercles of the posterior molars- 

 reduced, and an additional one on the anterior extremity of the first molar. 

 Superciliary ridges none, but the supraorbital borders converging towards^ 

 the middle line, and meeting above the postorbital region. No indication 

 of postfrontal processes. Infraorbital foramen rather large above, termi- 

 nating below in a vertical fissure. Incisive foramen entering the raaxillar}^ 

 bone extensively. Incisor teeth not grooved. 



I only know this genus from the cranium anterior to the pterygoid 

 region, the mandibles, and the dentition. These parts display the characters 

 of Muridce, and in particular of the existing genus Hesperomys. The only 

 character which I can find which has enabled me to distinguish Eumys front 

 the latter genus is the extension upwards of the orbital fossai so as to form, 

 an interorbital crest. In none of the Sigmodont genera of North America 

 are the supraorbital borders contracted in this way, but the crest is seen 

 in Fiber and in various degrees in the genus Arvicola, being as distinct ia 

 Eumys as in A. xanthognathus? 



A single species is certainly referable to this genus, the E. elegans,. 

 which was abundfint during the White River Mioceae epoch. 



The typical species was originally described by Leidy, who gave it 

 the generic name which I have adopted; but he at no time characterized 

 the genus, or showed how it differed from others already known. This was 

 first done by myself, as above cited. 



> Report of Lieut. G. W. Wheeler, IV, p. '.m, PI. LXIX, fig. 15 



