574 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 48. 



the Pleistocene, at least three distinct species of horses; and that 

 thus are confirmed conclusions which have been derived from studies 

 of skulls and teeth. It is to be hoped that soon limbs may be found 

 associated with skulls. 



EXPLANATION OF PLATES. 



Plate 30. 



Bison sylvestris. Type. 



Fig. 1. Right hinder angle of skull, seen from above. X £. 



2. Left side of rear of skull, seen from below. X£. 



1. Basioccipital. 2. Petrosal. 3. Basisphenoid. 4. Alisphenoid. 

 5. Pterygoid processes. 6. Occipital condyles. 7. Base of paroccipital 

 process. 8. Cavity into which opens the condylar foramen. 9. Fora- 

 men lacerum posterius. 10. External auditory meatus. 11. Postglenoid 

 foramen. 12. Glenoid fossa. 13. Foramen lacerum medius. 14. Fora- 

 men ovale, confluent with 13. 15. Bar of bone forming floor of foramen 

 lacerum anterius. 



3. Outer face of last premolar and two molars of right side of lower jaw. 



XI. 



4. Inner face of the same teeth. XI. 



Plate 31. 



Bootherium nivicolens. Type. X£. 



Fig. 1. Face view of forehead and horn-cores. 



Bootherium sargenti. Type. X.36. 



2. Side view of skull. 



Plate 32. 



Equus hatclieri. Type. X£. 

 Side view of skull. 



Plate 33. 



Equus Jiatcheri. Type. X£. 



Fig. 1. Face view of the skull. 

 2. Palatal view of the skull. 



Plate 34. 



Equus hatcheri. Type. Xf. 



Fig. 1. Grinding surface of the upper premolars and molars. 

 2. Grinding surface of lower premolars and molars. 



