484 PROCEEDINGS OF THE ACADEMY OF [1897. 



men but the interorbital width is 325 mm. greater. The horns of 

 both these specimens agree closely in size, curvature and relative 

 dimensions with the larger horn-core and attached frontal bone 

 forming the type of Leidy's Bison antiquus from Big Bone Lick, 

 Kentucky. 



Dr. J. A. Allen, in his Memoir of the American Bisons, 1 not only 

 shows the specific differences of the smaller extinct bison of America 

 from the living animal, but establishes the priority of Leidy's name 

 antiquus over Richardson's crassicornis, and shows that both these 

 names were, with little doubt, applied to the same species. In the 

 Museum of the Academy is the most complete cranium of fossil 

 American bison 2 yet recorded (PI. XII, fig. 2). It was sent to Dr. 

 Leidy by Messrs. Calvin and Wilfred Brown, who discovered it in 

 the Pilarcitos Valley near San Francisco, Cal. It is classed by 

 Leidy under latifrons, to which he subsequently referred his antiquus 

 specimens. Its relations to the existing bison are much closer, how- 

 ever, than to Leidy's type of antiquus. A comparison of the type 

 of antiquus from Big Bone Lick with the newly acquired specimens 

 from Alaska, confirms the views of Dr. Allen and Prof. E. D. Cope, s 

 viz., that we have in B. antiquus a near prototype of the existing 

 bison. In antiquus the stout, subcircular horn-cores have first a 

 lateral growth at right angles to the longitudinal axis of the skull 

 (or directed slightly backward) and on a level with (or slightly be- 

 low) the frontal plane, rather abruptly curving upward along their 

 distal third within a plane intersecting the frontals at right angles, 

 or at an angle from 5 to 15 degrees posterior thereto. In Bison bi- 

 son typical specimens show the following characteristic differences 

 from B. antiquus: a, the size of the cranium in largest known ex- 

 amples is 10 to 15 percent, less; b, the relative length of the horn- 

 cores to the breadth of frontals between the bases of horn-cores is 5 

 to 10 per cent, less; c, a straight line drawn from the tip of horn- 

 core across the median superior base of same in B. bison will, if con- 

 tinued, intersect the orbits ; in B. antiquus, a line similarly drawn 

 intersects the base of opposing horn-core — in other words, the chord 

 of the smallest arc in horn-cores of B. bison is at about an angle of 

 45° to the longitudinal axis of the skull, while in B. antiquus the 

 same chord is more or less nearly at right angles (90°) to that axis ; 



1 Mem. Mus. Comp. Zool., IV, 1876. 



2 Rep. U. S. Geol. Surv. Terr., I, p. 253, pi. 28, figs. 4 and 5. 



3 Jour. Acad. Nat. Sci., Phila., IX, p. 457. 



