NO. 2021. EXTINCT BISONS OF NORTH AMERICA— HAY. 185 



it is narrower as compared with that of the American Museum 

 specimen of B. occidentalis (pi. 10, fig. 1) and with that of the same 

 museum's specimen here described as Bison regius (p. 192, pi. 18, fig. 1). 



Seen m profile there is a prominence just in front of the occipital 

 crest. The forehead is somewhat swollen behind the line joining 

 the rear of the orbits. The nasals, where they join, are only slightly 

 convex, fore and aft. Between the orbits the face is nearly flat. 

 From the hinder edge of the hard palate to the fronto-nasal suture, 

 m the midline, is 182 mm., close to one- third of the basilar length. 

 The region occupyhig the front of the lachrymal and adjacent border 

 of the maxilla is more depressed than m Bison hison. The lachrymal 

 extends forward relatively farther than in Bison bison, its extremity 

 being halfway between the anterior process of the frontal and the 

 hinder end of the premaxilla. Wliile being considerably longer than 

 the same bone in Bison hison (138 mm. as compared with 110), the 

 width is almost exactly the same (51 mm.). The ascendmg processes 

 of the premaxillse are more strongly concave on their upper border 

 than m B. bison, and they approach nearer the nasals. The width of 

 the foramen magnum, near its upper border, is 43 mm.; at the same 

 place m B. bison the width is 50 mm. The vertical diameter is the 

 same in the two specimens compared. 



As might be expected, the lower jaw does not differ apparently from 

 that of B. bison, except in its slightly greater size. From the incisive 

 border to the angle it measures 457 mm. ; from the lower border, just m 

 front of the angle, to the summit of the articular surf ace, is 190; to 

 the summit of the coronoid process, is 240. The height of the bone, at 

 the rear of the last molar, is 78; at the front of the first true molar, 

 65; at the rear of the first premolar present (pm.g), 52; at the middle 

 of the diastema, 43. At the last pomt named the bone is 20 thick, 

 slightly less than in the specimen of B. bison at hand. 



On a comparison of the complete skull here described with the 

 rear of the skull with the horns. No. 2383, U.S.N.M. (pi. 15, fig. 3), it is 

 seen at once that the horns of the latter were larger at the base and 

 considerably longer. If, in each case, we divide the distance of the 

 tip from the base, taken in a straight Ime, into the length along the 

 lower curve and multiply this by 100, we obtain, m No. 2383, the 

 mdex about 130; m No. 7706, the index 128.2. 



Wliile there is this greater size of horns in No. 2383, the skull in 

 nearly all of its measurements is smaller, bemg greater only in the 

 height of the occipital crest and in the size of the foramen magnum. 

 Inasmuch as the sheaths of the horns of No. 2383 can not be detached, 

 the length of the horn-cores has been determined only approximately. 

 Figure 7 presents a view of the horn-cores of No. 7706, as seen from 

 behind. 



