520 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.48. 



in the existing bisons, and that consequently the brain cavity of the 

 former was actually and relatively narrower in front than in the 

 latter. As exactly as can be determined the width of the brain-case 

 of B. sylvestris, taken in the temporal fossa, over the auditory 

 meatus, was at least 110 mm. ; at the front of the glenoid articula- 

 tion, not more than 90 mm. In the cow bison, already several times 

 mentioned, the width at the rear position is 120 mm. ; at the anterior 

 position, 110 mm. In the jersey cow referred to above the measure- 

 ments are respectively 98 mm. and 82 mm. Therefore the brain- 

 case of B. sylvestris was narrowed forward almost exactly as in the 

 jersey cow and more rapidly than in the existing bisons. 



As nearly as the width of the skull can be determined it meas- 

 ured 180 mm. across the zygomatic arches at the glenoid fossae. In 

 the case of the cow bison this measurement is 200 mm. ; in the jersey 

 cow, 166 mm. From the rear of one temporal fossa to that of the 

 other is about 140 mm. 



In the existing bison of our country the skull, at the narrowest 

 place between the horns and the orbits, is at least as wide as it is 

 across the zygomatic arches, often much wider. In the jersey cow the 

 least width across the forehead is considerably less than across the 

 zygomatic arches ; and this appears to have been the condition in the 

 extinct species here described. As just mentioned, the width across 

 the glenoid fossae is 180 mm.; the least width across the forehead 

 seems to have been close to 140 mm. The forehead naturally pre- 

 sented an appearance quite different from that of Bison bison. 



So far as can be determined from the materials at hand, the parieto- 

 occipital suture on the upper surface of the skull was pushed back- 

 ward somewhat farther than in the American bison. In front of the 

 pedestal of the horn-core there is a sharp crest which separated the 

 temporal fossa from the forehead. In the existing biuon this region 

 is thick and obtuse. It is more acute in the jersey skull, but not so 

 acute as in the fossil. 



An apparent difference between the existing species of bison and the 

 fossil here described is found in the occipital condyles. In the fossil 

 the condyle is narrow near its lower anterior end; the least width 

 from its border at the foramen magnum to that near the excavation 

 containing the condylar foramen is about 21 mm. ; in the specimens 

 of Bison bison examined the width varies from 26 mm. to 33 mm. 

 Naturally other specimens of B. sylvestris might abolish this differ- 

 ence. 



The lower jaw is represented by the greater part of the horizontal 

 ramus of the right side. Only the hindermost part of the symphysis 

 is left, the bone being broken off just at the front of the mental 

 foramen. On the outer side the bone as preserved continues back- 



