412 University of California Publications in Geology 



[Vol. 7 



Measurements* op 



Dm 1 , anteroposterior diameter 



Dm 2 , anteroposterior diameter- 



Dm 2 , transverse diameter 



Dm 3 , anteroposterior diameter 



Dm 3 , transverse diameter 



Dm 4 , anteroposterior diameter 



Dm 4 , transverse diameter 



Di 1 , greatest transverse diameter 



Di 2 , greatest transverse diameter 



Di 3 , greatest transverse diameter 



Dm,, anteroposterior diameter 



Dm,, transverse diameter 



Dm,, anteroposterior diameter 



Dirij, transverse diameter 



Dm,, anteroposterior diameter 



Dm,, transverse diameter 



Di,, greatest transverse diameter 



Di,, greatest transverse diameter 



Di 3 , greatest transverse diameter 



Milk Dentition 



No. No. No. No. 



20099 a 19834 6 21072 c 19835 d 



7.5 mm ........ 



50 48 



24.6 24.8 



34 33 



26 26.5 



38 36.2 



24.5 26.2 



22.9 



25.8 



19. 



40 39.8 



14.2 14.8 



34. 34.9 



14.5 16.2 



37.2 34.6 



12.9 15.9 



17.8 



18.3 



14.5 



* Measurements taken in manner indicated in discussion on page 409. 



a, M 1 just emerging through jaw. 



b, M 1 erupting. 



c, M, showing first traces of wear. 



d, M,in function, M, erupting. 



COMPAEISON WITH EQUUS CABALLUS 



The skulls of Rancho La Brea horses have approximately 

 the size seen in the modern domesticated horse, but range up- 

 ward to dimensions greater than those of the average domesti- 

 cated horse. They differ from Equus caballus in the shorter 

 and wider nose, more convex forehead, narrower occiput, and 

 more massive lower jaw. The mandible is very noticably higher 

 below the premolars and the diastema. 



The dentition of the Rancho La Brea species differs from 

 that of Equus caballus in the more simple pattern of the enamel 

 of the cheek-teeth. The dimensions do not differ markedly. 



