198 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.46. 



b*. Horn-cores more elongated and directed considerably downward prox- 

 imally; tips rising little above the face; the sheaths directed upward 

 distally; the length of the cores exceeding the distance between 

 the bases by from 24 to 70 per cent, and the circumference of the base 

 by from 21 to 40 per cent; index of curvature about 125. . crassicornis . 



¥. Horn-cores not sagging at the base; directed outward, upward, and 

 Bomewhat backward; exceeding the distance between the bases by 

 about 40 per cent, and the circumference of the base by from 22 to 32 

 per cent; index of curvature about 130; tips of honi-sheaths directed 

 strongly inward alleni. 



fcs. Horn-cores long, heavy, and moderately curved; length along upper 

 curve more than twice the distance between the bases and 

 exceeding by more than 50 per cent the circumference at the base; 

 index of curvature 110. Teeth with the enamel of the "lakes" 

 very simple latifrons. 



V. Horn-cores, as indicated by the type, longer, slenderer, and more curved 

 than in B. latifrons; length along the upper curve two and a half 

 times the distance between the bases and exceeding the circumfer- 

 ence of the base by 90 per cent; index of curvature about 130. Teeth 

 with the enamel of the ' ' lakes " with reentering folds regius. 



EXPLANATION OF PLATES. 



Plate 8. 



Skulls of Old World bisons known as Bison priscus. 



Fig. 1.— Skull found near Pavia, Italy. After H. v. Meyer. 



2.— Skull supposed to have been found in Hungary. After H. v. Meyer. 

 3.— Skull showing horns, found in Siberia. After P. S. Pallas. 



Plate 9. 

 Skulls of Bison priscus and B. occidentalis. 

 Fig. 1. — Dorsal view of skull in British Museum of Natural History and known as 

 Bison priscus. From a cast. 

 2. — Rear view of same skull. From a cast. 

 3. — Dorsal view of skull of the type of Bison occidentalis, No. 4157, United States 



National Museum. 

 4. — Rear view of same skull. 



Plate 10. 



Skulls of Bison occidentalis. 

 Fig. 1.— Dorsal view of skull found in Yukon Territory, No. 13721, American Museum 

 of Natural History. 

 2. — Rear view of same skull. 



3a.— Oblique view of same skull. After Quackenbush. 

 3c.— Dorsal view of skull showing horns, Yuton Territory. After Quackenbush, 



Plate 11. 

 Skulls of Bison occidentalis. 

 X.'ig. 1.— Dorsal view of Alaskan skull, No. 5514, United States National Museimi. 

 2. — Rear view of same skull. 

 3.— Dorsal view of skull from Yukon Territory, No. 2643, United States National 



Museum. 

 4. — Rear view of same skull. 



