436 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 53. 



The following measurements have been obtained from the skull : 

 Measurements of the skull. 

 From middle of incisive border to front of foramen magnum (basilar 



length) 446 



From middle of Incisive border to front of posterior nares 245 



From middle of incisive border to naso-premaxillary notch 167 



From middle of incisive border to middle of occipital crest (vertex 



length) 498 



From middle of incisive border to front of pm^ direct 120 



From middle of incisive border to front of orbit o02 



From middle of incisive border to middle of line joining hinder borders 



of orbits (facial length) 343 



From middle of incisive border to rear of orbit direct 357 



From rear of orbit to middle of occipital crest 188 



From occipital crest to middle of line joining rears of orbits (cranial 



length) 100 



From rear of hard palate to notch in vomer 93 



From notch in vomer to front of foramen magnum 116 



Width across mastoid processes 102 



Width across glenoid fossae 187 



Width from outside to outside of parastyles of last molars 120 



Width from outside to outside of last premolars 118 



Width from outside to outside of outer incisors 72 



Width of the face at the front of the orbits 152 



Width at the rear of the orbits (frontal width) 198 



Width on the maxillary ridges at maxillo-malar suture 171 



Width of palate at last molars 65 



Width of palate at pm', least 47 



Width of palate at diastema, least 43 



Length of orbit 54 



From front of symphysis of lower jaw to rear of ascending ramus 385 



Length of symphysis ' 80 



Height of jaw of front of mi 81 



i^rom front of symphysis to front of pm2 108 



In 1915 ^ the writer presented a table which gave various measure- 

 ments and indices derived from the measurements of the skulls of 

 16 individuals of Equus caballus. The measurements were taken 

 from a table prepared by Nehring.^ Eight of these skulls were those 

 of small horses, and the basilar lengths ranged from 426 mm. to 

 452 mm. In the other eight the basilar length varied from 536 

 mm. to 585 mm. By consulting the writer's table or that of Neh- 

 ring it will be found that the short skulls are relatively broader 

 than the larger ones, the cephalic index (= frontal width X 100 -^ 

 basilar length) varying from 42 to 45.9. The average is 44.2. In 

 the long-headed horses the cephalic index varies from 38.9 to 43.6, 

 the averages in the eight horses being 41.1. In the Yukon slmll 

 here described the cephalic index is 44.4, which shows that the species 

 belonged among the small horses having broad skulls. 



iProc. U. S. Nat. Mus., vol. 48, p. 559. 

 ^ "Landwlrthsch. Jahrb., vol. 13, 1884, p. 81. 



