NO. 2 EXTINCT HORSE FROM ALASKA HAY 3 



EQUUS NIOBRARENSIS ALASKJE, new subspecies 

 Skull somewhat smaller than in the typical form ; premaxillse rela- 

 tively wider, and differing- in outline ; region about articulation of the 

 lower jaw and zygomatic arch modified. 



The differences between this form and that found in Nebraska will 

 appear in greater detail as the description proceeds. It is especially 

 to be noted that the Alaskan horse is considerably smaller than the 

 other. The type of Equus niobrarensis was found at Hay Springs, 

 in northwestern Nebraska ; but other members of the species have 

 been recognized in teeth from western Texas, eastern Nebraska, and 

 western Iowa. A lower molar, found at Wathena, Kansas, is referred 

 to the same species. The deposits at Hay Springs are known as 

 the Sheridan, or Equus, beds. The teeth from Iowa occur in the 

 Aftonian, as do probably those from eastern Kansas and western 

 Nebraska. 



The following measurements have been taken from the skull and 

 the teeth ; and these are accompanied by the corresponding measure- 

 ments of the type Equus niobrarensis, No. 4999, U. S. National 

 Museum : 



Measurements of Skull and Teeth of E. niobrarensis. 



No. 7700 No. 4999 

 mm. mm. 



i. From middle of incisive border to rear of occipital condyles. .518 556 



2. From middle of incisive border to front of foramen magnum. .498 530 



3. From middle of incisive border to rear of hard palate 268 290 



4. From middle of incisive border to rear of occipital crest 540 582 



5. From middle of incisive border to line joining fronts of pm. 2 . .129 137 



6. From middle of incisive border to line joining the rear of the 



orbits 368 400 



7. From middle of occipital crest to line joining the rear of the 



orbits 174 181 



8. Length of the orbit 65 84 



9. Distance between i. 3 and pm. 2 93 I0 5 



10. Width across post tympanic processes 117 IV J 



11. Width across glenoid fossae 195 217 



12. Width at rear of orbits 220 240 



13. Width at front of orbits 158 158 



14. Width on maxillary ridge at maxillo-malar suture 182 187 



15. Width of palate at m. 3 7^ 70 



16. Width of palate at pm. 2 , least 5° 5° 



17. Width of palate at diastema, least 54 45 



18. Width from outside to outside of m. s 124 123 



19. Width from outside to outside of pm. 4 128 125 



20. Width from outside to outside of canines 68 



