486 PROCEEDINGS OF THE ACADEMY OF [1897. 



ship to the huge-horned B. latifrons of Harlan, the type of which is 

 in the Museum of the Academy. It is, however, a much smaller- 

 horned species, and the horn-cores are much more curved and flat- 

 tened than in latifrons. The difference in the size of the cranium 

 in the two species is not great, the frontal breadth being the 

 same, but the greater breadth and massive development of the occi- 

 pital region in latifrons is very noticeable, a difference necessitated 

 by the great relative weight of the horns and the consequent de- 

 velopment of the cervical muscles and their attachments at the base 

 of the cranium. The species to which No. 13,754 shows closest rela- 

 tions is B. crampianus of Cope, recently described, 5 from the Pleis- 

 tocene of Kansas, the type of which is also in the Museum of the 

 Academy. 



The horn-core and rostral portion of cranium which represent 

 this species are intermediate in size and characters between latifrons 

 and No 13,754. 



As pointed out by Prof. Cope, the characters separating latifrons 

 from crampianus, based solely on the horn-cores, are, without much 

 doubt, specific, the difference in size alone amounting to 40 per cent., 

 while in curvature and the relative dimensions of cross section the 

 distinctions are equally pronounced. 



It therefore remains to consider the status of the Alaskan speci- 

 men with regard to crampianus. Before doing so, however, the 

 question of sexual differences in the development of the horn-cores 

 of the genus Bos and Bison should be considered. Dr. Leidy, in 

 his study of the extinct bisons, evidently believed, or at least thought 

 it possible, that sexual variations in size of horn-cores of the extinct 

 bisons might account for some of the so-called species described by 

 himself and others, and, subsequent to describing antiquus as a dis- 

 tinct species, he made it a synonym of latifrons ! The extreme im- 

 probability of this conjecture is made evident by*Dr. Allen in his 

 monograph. It is impossible to determine the sex of fossil speci- 

 mens, except where they are perfect enough and numerous enough 

 to exhibit the characters which determine this in nearly related liv- 

 ing species. The number of specimens of fossil bisons is yet too 

 small and their condition too fragmentary to arrive at a very satis- 

 factory answer to this question. So far as it goes, however, it is 

 pertinent to show the extent of difference in the size and shape of 



6 Jour. Acad. Nat. Sci., IV, p. 456, pi. XXII : (= B. all mi Marsh). 



