^ ft ■ 



INTO. 12. 



ON SOME EOCENE MAMMALS, OBTAINED BY HAYDEN'S 

 GEOLOGICAL SURVEY OF 1872. 



By Edward D. Cope, A. M. 



(Bead before tJie American Philosophical Society, , 1873.) 



Hyopsodus paulus. Leidy. 



Hayden's Survey, Montana, etc., 1871, p. 363. 

 From Cottonwood and South Bitter Creeks. 



Microsyops vicarius. Cope, sp. nov. 

 Founded on portions of the mandibular rami of two individuals from 

 the Bad Lands of Cottonwood Creek, Wyoming. These represent an 

 animal considerably smaller than the Hyopsodus paulus, and with prob- 

 ably only three premolars. This is believed to be the fact from the small 

 size of the last premolar, and the anterior contraction of the first molar. 

 The molars have no external cingulum nor antero-external tuberosity 

 described to exist in the M. gracilis, by Marsh. The cones have simple 

 apices, and the oblique connecting ridges of both genera. 



H. paulus. M. vicarius. 

 M. M. 



Length of three molars 0.0136 0.0115 



last molar 052 .0045 



" first molar 040 .0038 



Width " anteriorly 041 .0026 



" " posteriorly 043 .0029 



Antiacodon pygm^eus, Cope. 

 Lophiotherium pygmceum, Cope. Proceed. Amer. Philos. Soc, 1872, 

 Extras July 29th. Antiacodon venustus, Marsh, Amer. Journ. Sci. Arts, 

 1872 (published, August 13th). Hyopsodus pygmceus, Cope, loc. cit., p. 

 461. From Cottonwood Creek, Wyoming. 



Antiacodon furcatus. Cope, sp. nov. 

 Established on a part of the right ramus mandibuli with the three 

 molars and last premolar in perfect preservation. The crowns of the 

 molars are composed of two external chevron-shaped tubercles, the apices 

 rising as acute cusps, and two internal cones, the interior of which is 

 flattened and strongly bifid, both points being more elevated than any of 

 the others. The cusps are nearly opposite to each other, and behind the 

 interval between the two posterior rises another, not so elevated as the 

 others, except on the posterior molar. Here it is elevated, and nearly 

 equidistant from the two in front of it. The enamel is smooth, and there 

 is no cingulum on either side. The premolar consists of a principal sec- 

 torial cusp, and has a smaller but stout acute anterior cusp, with a small 

 rudiment of another behind ; a stout cusp l'ises from the inner posterior 

 margin of the principal one, giving it a subbifid appearance. 



