1916] Chandler: Skull and Dentition of Bison antiquus 



131 



the breadth in B. antiquus in both sexes is one and a third times that 

 in the corresponding sex of the modern species. There is no notice- 

 able difference in size of the orbits. The nasal bones of B. antiquus 

 differ from those of B. bison in being relatively shorter and broader, 

 and less arched, tapering more gradually to the tip ; so that the notch 

 near the distal end is not so conspicuous. These differences are well 

 brought out by a comparison of figures 6 and 7, and of the measure- 

 ments in Table I. 



The horn-cores are longer and relatively more slender in B. antiquus 

 than in B. bison, the length of the horn-cores in the females of the 

 former about equalling that of the males of the latter, the basal cir- 

 cumference, however, being much greater in the males of B. bison 

 than in the females of B. antiquus, but not as great as in the males 

 of the latter. As previously stated, the angle of growth of the horn- 

 cores is considerably different in B. antiquus from that in other Ameri- 

 can species, or in B. bonasus, but the curvature is much the same, there 

 being a sagging below the level of the forehead, then an even upward 

 curvature, and a more or less pronounced reflexion of the tips. (Com- 

 pare figs. 5a and 5b, with figs. 1^4.) In B. bonasus the horn-cores seem 

 to be relatively even smaller than in B. bison, but the difference in 

 skull and horn-cores between B. antiquus and either of the modern 

 species is greater in every respect than that between the two existing 

 species. 



DENTITION 



The dentition is known by teeth in many stages of wear, that of 

 the lower jaw being especially well represented. The teeth of bison 

 are of little value from a systematic point of view, the individual 

 variation within a species so far overbalancing any average specific 

 difference that may exist that it is difficult to find any constant, reliable 

 specific difference except in size. Hay 15 has shown that the amount 

 of complication of the enamel walls of the lakes of the molars shows a 

 tendency to vary specifically, B. latifrons having a very simple pattern, 

 and B. regius relatively a very complicated one. Hay states that in 

 several Recent specimens of B. bison he finds no inflexion of the enamel 

 on the sides of the lakes of the upper molars, and this statement is 

 borne out by my own observations. Allen 16 figures a specimen of B. 



is Op. cit. 

 ie Op. cit. 



