with Descriptions of Neiv Forms. 173 



The major distinctions between this form and Para- 

 daphcenus are: (1) much larger size than any species of 

 the latter genus; (2) M 3 absolutely very much larger, 

 for in Paradaphcenus and Daphamus this tooth is a small 

 convex nub; and (3) presence of posterior cusp on P 3 . 

 From Temnocyon it differs in being smaller, with the heels 

 of Mj and M 2 very much less trenchant ; with both pro- 

 tocoled and metaconid of M 2 on anterior half, and with 

 posterior cusp on P 3 . Mj is not medially constricted as 

 in T. altigenis, nor is the posterior cusp of P 4 so exter- 

 nally situated in this new form. Mesocyon has anterior 

 basal tubercles on P 3 and P 4 , which are lacking in Pericyon. 

 The heels of P 4 and of M x are much larger than in Meso- 

 cyon, and the posterior cusp of P 4 is higher and much more 

 prominent. Mesocyon is smaller, with the premolars less 

 compressed. 



From Teplirocyon, Pericyon is differentiated by the 

 much larger M 3 ; the different arrangement of the conids 

 and heel of M 2 ; the much more marked lateral compres- 

 sion of the premolars, their greater degree of hypsodonty, 

 and the smaller posterior cusp on P 3 , as well as the larger 

 size ; the greater area occupied by the masseteric fossa 

 and the much less steeply inclined postero-inf erior border 

 of the ramus below the coronoid process, the anterior bor- 

 der of which rises more nearly vertically in Teplirocyon 

 than in the new genus. Teplirocyon is Middle Miocene ; 

 Pericyon, Upper Oligocene. 



Measurements of Holotype. 



mm. 



Length of dental series with canine 85.5 



Length of molar series 35 



Length of premolar series 40 



Depth of ramus below middle of M 2 22 



Ant.-post. diameter of M 1 17 



Ant.-post. diameter of M^ 11 



Ant.-post. diameter of M 3 8 



Enhydrocyon oregonensis, sp. nov. 



(Figs. 4 and 5.) 



Holotype, Cat. No. 12730, Y. P. M. Skull lacking posterior and basi- 

 cranial areas of cranium. Upper Oligocene (middle John Day), Turtle Cove, 

 John Day Valley, Oregon. 



This species is much smaller than E. basilatus and E. 



