R. 8. Lull — New Tertiary Artio dactyls. 107 



Hyoid (tig. 5). — A pair of hyoid elements are present, 

 representing the right and left stylohyals or great cornu. 

 Of these, the right is complete for its entire length. Com- 

 pared with the equivalent bone of Antilocapra, the fossil 

 is somewhat more robust in proportion to its length, the 

 distal end is flatter and more expanded, bnt while the 

 proximal articular portion is more robust, the muscular 

 angle is much more slender. In Antilocapra, this has a 

 marked fore and aft expansion. In Aletomeryx, the 

 angle corresponds more nearly with that of the ox. It is 

 the place of origin of the stylohyoid muscle, the action 

 of which is to draw the base of the tongue upward and 

 backward. The significance of the relative development 

 of this muscle is, however, not clear. 



Vertebral Column (Figs. 9-13). 



The vertebral formula is assumed to be that of the 

 prongbuck 10 — cervical 7, thoracic 13, lumbar 6, sacral 4, 

 caudal? — which in turn compares with the ruminants in 

 general except for the reciprocal variation of 13 thoracic 

 to 6 lumbar or 14 thoracic to 5 lumbar. As there is no 

 complete series of vertebrse pertaining to a single individ- 

 ual, there is here a chance for error. 



The vertebral column as a whole is about 700 mm. long, 

 and the regional measurements as compared with those 

 of Antilocapra (female) No. 180 follow: 



Aletomeryx Antilocapra 

 No. 180 





m. 



m. 





Eatio 



Cervical 



... -0203 



•0335 





1-75 



Thoracic 



... -0245 



•0335 





1-364 



Lumbar 



... -0193 



•0245 





1-464 



Sacral 



... -0066 



•0086* 



Av 



1-30+ 



Total 



. ... -0707 



•1001 



. 1-475 



* Four sacrals. 











Cervical vertebra. Atlas (fig. 9). — This bone re- 

 sembles that of Antilocapra very closely, differing mainly 

 in that the outer margins of the wings are more nearly 



10 In both Antilocapra skeletons before me the sacrum consists of five 

 vertebrae, but four is the number given in Flower's Osteology. 



