128 Wortman — Studies of Eocene Mammalia, etc. 



species of turtles that inhabited the Bridger lake, and this is 

 rendered all the more probable by the presence in these 

 deposits of coprolites of some large carnivorous Mammal, 

 which contain fragments of turtle shell. While it is not 

 known with certainty to what species these coprolites pertain, 

 it is, I think, in connection with the probable aquatic habits of 

 the species, a fair presumption that they refer to Patriofelis. 

 The great wear of the teeth as well as the power of the jaws 

 accord well, moreover, with the view that they were used for 

 crushing the strong bony coverings of the turtles, which may 

 be said to have literally swarmed in the tropical or semi-tropi- 

 cal waters of the ancient lake or river as the case may be. 

 The suggestion of Osborn that the specialization of the teeth 

 and the increase in the size of the jaws are reasons for disbe- 

 lieving in its aquatic habits has little force. An exactly paral- 

 lel case is seen in Potamotherium and Lutra (ancestor and 

 descendant), in which the same thing has occurred. The teeth 

 have been reduced in number, enlarged and specialized, and 

 the jaws shortened and increased in size, notwithstanding 

 Lutra is to-day preeminently a fish eater. 



Touching their relationship to the Pinnipedia I have no new 

 facts to add. I have not asserted that the seals have been 

 derived from any known species of Patriofelis, but that they 

 rnay have been derived from some as yet undiscovered member 

 of this group, and the reasons for such a belief, which have 

 already been fully stated, have not, to my mind, been in any 

 way affected by this restudy of the subject on the part of Pro- 

 fessor Osborn. 



Subfamily TAmnocyoninm. 



As already remarked, this group appears for the first time in 

 the Bridger and continues into the IJinta. According to our 

 present understanding, the three or four American species 

 appear to be best classified in the single genus Limnocyon, 

 although it is not altogether improbable that two of them, 

 when more fully known, will require to be placed in separate 

 genera. The European representative of this subfamily, 

 Thereutherium, is distinct and shows a considerable advance 

 over the American species in the matter of tooth specializa- 

 tion. The two genera may be distinguished as follows : 



First premolar above and below two-rooted ; last superior molar 

 transverse, relatively large, with three well-developed roots and 

 external and internal cusps ; inferior molars with moderate-sized 

 basin-shaped heels and internal cusps. Limnocyon. 



First superior premolar above and below single-rooted ; last 

 superior molar much reduced, vestigial ; heels of inferior molars 

 reduced, and internal cusps vestigial or absent. Thereutherium. 



[To be continued.] 



