204: Wortman — Studies of Eocene Mammalia in the 



like all the Creodonts, the posteroexternal angle enlarged and 

 produced into a cutting blade. It is upon this tooth that the 

 sectorial specialization has centered, whereas in the otters it is 

 the fourth premolar. The superficial likeness to the aquatic 

 mustelines is very evident, however, and I do not hesitate to 

 venture the opinion that this species was aquatic or partially 

 so in its habits. The resemblances to the Insectivora seen in 

 the base of the skull are very marked, and there is a possibility 

 that the entire group may belong to this order instead of to the 

 Creodonta. 



The measurements of the species are as follows : 

 Type of Zimnocyon velox : 



Length of molar and premolar series . _ SO'S 111111 



Full length of jaw (estimated) 53* 



Length of molars _ 11* 



Depth of jaw at last molar 8 • 



Other specimens : 



Height of occiput above base of condyles 12- 



Width of condyles _ 15 • 



Width of occiput _ 15 *5 



Width of base of skull between mastoids (outside). 22- 



Length of two superior molars 7*3 



Width of first molar (in front) . _ .. 4*8 



Width of last molar 5*4 



Length of humerus _ _ _ _ _ _ 40'5 



Antero-posterior diameter of head of humerus 7 *5 



Transverse diameter of distal end of humerus 9*5 



Length of olecranon of ulna ._ 5* 



Length of metapodial of pollex J. 7'5 



Length of a first phalanx of manus __ 8* 



The type specimen was found by Professor Marsh at Grizzly 

 Buttes, in the Bridger Basin, and others were collected at 

 Millersville. The horizon for the species is therefore near the 

 base of the deposits. 



TAmnocyon medius, sp. nov. 



Numerous remains of a species intermediate in size between 

 L. verus and L. velox are contained in the collection, but 

 unfortunately they are for the most part rather fragmentary. 

 One specimen, figures 81, 82, which I select as the type, con- 

 sists of the greater j)art of both lower laws, associated with the 

 upper molars and a part of the premolar dentition. The prin- 

 cipal differences, besides those of size, are seen in the superior 

 molars. In L. verus and L. velox the two external cusps of 





