201 Wortman — Studies of Eocene Mammalia in the 



As a whole, the milk dentition of the fossil differs from that 

 of both the Canidse and the Yiverridse in having three instead 

 of four milk molars ; from the Hysenidse in the larger canine, 

 the small, single-rooted first molar, and the development of 

 three strong cusps on the second. In the hyaena, the first 

 deciduous molar is large and two-rooted, and the anterior basal 

 cusp on the second is rudimental or wanting. As far, how- 

 ever, as w r e are able to judge, in its imperfectly preserved con- 

 dition, it agrees perfectly with that of the cats. 



The crown of the sectorial is of much interest, inasmuch as 

 it exhibits a stage of development intermediate between that 

 of Dalceonictis of the Wasatch and Dinictis of the Oligocene. 

 The three usual cusps of the trigon are present, but they are 

 flattened and their edges drawn out to a much greater extent 

 than in any other Carnassident of its time. The internal cusp 

 is relatively small, has a very posterior position, and there is 

 no evidence that the posterior shear between it and the ante- 

 rior edge of the first superior molar was functional, which 

 leads to the conclusion that this latter tooth was considerably 

 reduced. The heel is composed of a single, rather large trihe- 

 dral cusp, with the anterior edge produced forwards toward 

 the base of the trigon, thus very strongly foreshadowing the 

 trenchant heel of the corresponding tooth of Dinictis, Nim- 

 ravus, and so many other Felines of the Oligocene and 

 Miocene. 



As already noted, a part of the bony crypt w T hich served to 

 lodge the germ of a second molar is to be seen just posterior 

 to the sectorial. Aside from the important fact of demonstra- 

 ting the existence of a second molar, it furnished the further 

 information that this tooth was much reduced in size, which 

 is of still greater moment. The jaw has greater vertical depth 

 in front than behind, the symphysis is large, but there is no 

 trace of a flange as in Dinictis. Altogether it may be remarked 

 that it is just such a type as preceded that of the Sabre-tooth 

 Tigers. 



The measurements are as follows : 



Length from anterior base of canine to posterior 



part of first permanent molar 59* mru 



Length of second and third deciduous molars. 33- 



Length of first permanent molar 18*5 



Depth of jaw at first deciduous molar ._ 32* 



Depth of jaw behind first permanent molar.. _ 23*5 



This important type specimen was found by Mr. G. M. 

 Keasby of the Yale party of 1871, in the Henry's Fork Bad 

 Lands of the Eridger Basin, Wyoming. 



