38 KANSAS UNIVERSITV QUARTERLY. 



the same drawing, and, after stating that the species is best known 

 from the Kansas University specimen, in the face of Dr. Williston's 

 description and figure, states as a characteristic of the species, that 

 "the postero-internal cusp is wanting." Now since this cusp is 

 as strongly developed in the Kansas University specimen as in 

 H. primcvvus or H. robi/sfiis, as specimens before me show, if Mr. 

 Adams is correct in his statement that H. occidcntalis does not have 

 the cusp, then we have to do with two distinct species. 



In Leidy's type there is little more than the number and size of 

 the teeth in the lower molar series, the form of the fourth premo- 

 lar, and the general size and shape of the body of the ramus, upon 

 which comparison can be based. Below is given a series of measure- 

 ments in which the Kansas University specimens are compared 

 with Leidy's figure and with the above-mentioned American 

 Museum specimen by means of data kindly furnished me by Dr. 

 Osborn. All measurements are given in millimeters. 



Leidy's Am. Kans. Univ. 

 Type. Mus, Smaller. Larger. 



Length from condyle to alveolar border. . . 170 168 



Molar series, length ! 47 75 46 



Breadth of base of third premolar og 09 



Breadth of base of fourth premolar 15 16 



Breadth of base of sectorial 21 20 



Depth of symphysis 65 (?) 63 72 



Depth of flange from base of canine 63.5 67 78 



Depth of mandible at base of fourth premolar 30 30 



Condyle to angle 25 27 



Length of diastema 37 41 48 



It will be observed that, so far as can be determined by measure- 

 ments, the Kansas University specimen agrees very closely with 

 Leidy's type. The fourth premolar is similar in size and shape to 

 the one remaining tooth, and, like it, is directed somewhat back- 

 ward. On the other hand, the mandible of the American Museum 

 specimen is slightly larger, has a more retreating coronoid process, a 

 shallower flange, a shorter diastema, and is longer from the sectorial 

 to the condyle. However, these differences are no greater than 

 those between the two Kansas specimens, and unless the absence 

 of the postero-internal cusp be found constant, the differences 

 would not seem to be specific. Then, so far as can be determined 

 by comparison, D. atrox and H. occidcntalis agree as closely as 

 individuals of the same species may be expected to agree, and, as 

 Mr. Adams suggests, may be regarded as identical. Moreover, the 



