MORRISON MAMMALS: PANTOTHERIA 69 



in the diagnoses are not thoroughly satisfactory and it is quite probable that some of 

 them will prove to be due to diflferenccs of preservation or to individual variation, but 

 it is probable that the species are distinct. The type is badly worn and broken and many 

 of its characters are obscured, but these may be made out with little doubt by compari- 

 son with the referred specimens. 



Dentition 



The advanced wear on the type has had the effect of increasing the length of the 

 talonid at the expense of the trigonid, attenuating the cusps, changing their relative 

 heights, etc., so that a casual inspection would seem to warrant generic separation, but 

 this is not confirmed by detailed study. As seen especially in Y.P.M. Nos. 13728 and 

 13730, the molars agree closely with those of A. gracilis but they are somewhat 

 smaller. The talonid is also shorter and narrows more rapidly in passing toward the 

 external side of the tooth. Probably correlated with this is the relatively feeble develop- 

 ment of the external cingulum. The paraconid seems somewhat less strong, although 

 this is a character readily modified by even a slight degree of wear. M-, is apparently 

 the longest tooth of the series, rather than Me, although the latter was probably higher. 

 and the disparity in length between Me and M7 is certainly greater than in A. gracilis. 



Mandible 



The horizontal ramus is stouter in proportion to the very diminutive teeth than in 

 A. gracilis. In the t)^e there are apparently three mental foramina, one beneath the 

 anterior root of Pi, one beneath Po, and one beneath the anterior root of P3. The other 

 mandibular characters, so far as surely known, are like those of A. gracilis. 



Measurements 



Of all the minute mammals of the American Jurassic, this species is apparently 

 the smallest. The measurements of the type are not very accurate, as the teeth are so 

 worn. 



Kepolesies Simpson 1927 

 1927. Kefolestes, Simpson, Amer. Jour. Set. (5) XIH, 413. 



Definition. — Metaconid of molars simple, squarely truncate at end; paraconid 

 curving forward and upward, about as high as metaconid, separated from me'' by a 

 wide U-shaped notch ; pa"", me'' and talonid cusp in a straight anteroposterior line. 



