Cope.] J-4o | Dec. 16, 



Two fractured crania exhibit the entire dentition of this species, and 

 give the generic characters satisfactorily. The dental formula is, I. § ; 

 C. | ; P-ni. ^-; M. f. The first superior incisor is large, and the crown is 

 somewhat spoon-shaped. The second iucisor is as robust as the first, but 

 the crown is shorter. The second premolar has one external and one in- 

 ternal lobe, in the third (fourth) premolar these lobes are much enlarged, 

 and the tooth is transverse. The true molars have two external cusps, 

 which are flattened, close together, and well within the margin of the 

 base of the crown. There is one internal lobe and a strong posterior 

 ledge, as in the opossums. Of the inferior incisors, the median is large 

 and half gliriform, while the first and third are small. The inferior, like 

 the superior canines, are large. The first and second (third) premolars 

 have no internal lobes, but the second (third) has a heel. The fourth is 

 more or less like the first true molar. 



The specimens show that my original determinations of the incisors 

 based on loose teeth we're correct. They also show that this genus is not 

 far removed from the more rodent-like genus Anchippodus cf Leidy. 



There are several species of the genus, which I define as follows : 



I. Fourth inferior premolar like first true molar. 



Larger ; third superior premolar larger ; fourth premolar with the external 

 cusp bilobate E. acutidens. 



Medium ; third superior premolar smaller ; fourth premolar with external 



cusp simple ; superior incisors wide ; large inferior narrower 



E. burmeisteri. 



Medium ; superior incisors narrow ; large inferior wider. . . .E. bisulcatus. 



II. Fourth inferior premolar with anterior V open and cutting. 

 Smallest ; incisors unknown E. acer. 



A species of the size of E. acer has been named E. spatularius, but I 

 cannot place it in the above key, as the premolar and incisor teeth are un- 

 known. The section II, approximates nearer the genus Oonoryctes than 

 sect. I. 



Mesodonta. 



HYOPSODUS LEJtOINIAiStTJS, Sp. nOV. 



This Mesodont is distinguished from the known species of the genus by 

 its superior size, and the fully developed heel of the interior third molar. 

 The anterior inner cusps of the inferior molars are absolutely simple, and 

 the same teeth have a weak external and no internal cingulum. The cusps 

 are elevated and the enamel smooth. 



The species of this genus known to me by their mandibles are four, and 

 these differ chiefly in' size. Their characters are as follows : 



Length of true molars M. .0165 ; last molar elongate H. lemoinianus. 



Length of true molars M. .0140 ; last molar longer than second 



//. paulus. 



