202 Wortman — New American Species of Amphicyon. 



Middle Miocene deposits of this country. It is represented by 

 at least two species from the John Day beds of Oregon and is 

 not uncommon. In the structure of the superior molars this 

 genus agrees closely with Amphicyon, in that the crowns are 

 symmetrical and much extended transversely; the last molar, 

 moreover, is but little pushed inwards and the cusps and ridges 

 are relatively high and prominent. There is no apparent 

 reduction in the size of any of the premolars, a fact which 

 would indicate that any species of Paradaphcenus thus far 

 known cannot be regarded as directly ancestral to Amphicyon. 



In the underlying White River beds comes the genus 

 Daphcenus Leidy, represented by at least four well-marked 

 species of rather common occurrence. In this group the 

 ridges and cusps of the molars are characteristically low and 

 blunt, the crowns of the upper molars are less symmetrical 

 transversely, and the third molar is pushed inward on a line 

 with the internal cusps. In any of the known species the 

 premolars are not reduced in size to any very noticeable extent. 

 It will be seen, therefore, that the genus is still further 

 removed from Amphicyon in its dental anatomy, and on this 

 account must be regarded as off the direct line of ancestry of 

 Amphicyon. Next below the White River species is found 

 the genus Prodaphcenus W. and M.* from the Uinta or upper- 

 most Eocene, and although but a single specimen consisting of 

 a portion of a superior maxillary is known, yet it serves to 

 indicate with certainty the existence of a three-molared type of 

 the Canidse in this horizon. This genus is again preceded in 

 the Bridger beds by Uintacyon Leidy, which has numerous 

 species reaching as far back as the Wasatch or Lower Eocene. 



That which is of especial interest to us in this connection is 

 the fact that certain species of Uintacyon and the only known 

 species of Prodaphmnus show a marked reduction in the size 

 of the premolars, possessing at the same time a type of molar 

 pattern which could have easily passed into that of Amphi- 

 cyon and thence into the bears. The likeness is not confined 

 to the upper molars, but extends to the lower molars and 

 canines as well. While the materials now known are perhaps 

 too fragmentary and scattering to hazard a definite opinion, 

 yet the resemblances between Amphicyon and these Eocene 

 forms are so striking that I cannot believe them altogether 

 due to accident. If this surmise of genetic affinity is correct 

 it will go far towards clearing up the origin of this peculiar 

 and important group of the Canidse. 



* Bull. Amer. Mus. Nat. Hist., June, 1899, p. 115. 



