EQUID^E 391 



development of the whole anterior arch of the hyoid. This con- 

 sists mainly of a long and compressed stylohyal, expanded at the 

 upper end, where it sends off a triangular posterior process. The 

 basihyal is remarkable for the long, median, pointed, compressed 

 "glossohyal" process, which it sends forward from its anterior 

 border into the base of the tongue. A similar but less developed 

 process is found in the Rhinoceros. The mandible is largely 

 developed, especially the region of the angle, which is expanded 

 and flattened, giving great surface for the attachment of the 

 masseter muscle. The condyle is greatly elevated above the 

 alveolar border ; its articular surface is very wide transversely, and 

 narrow and convex from before backwards. The coronoid process 

 is slender, straight, and inclined backwards. The horizontal ramus, 

 long, straight, and compressed, gradually narrows towards the 

 symphysis, where it expands laterally to form with the ankylosed 

 opposite ramus the wide, semicircular, shallow alveolar border for 

 the incisor teeth. 



The vertebral column consists of seven cervical, eighteen dorsal, 

 six lumbar, five sacral, and fifteen to eighteen caudal vertebrae. 

 There may be nineteen rib-bearing vertebrae, in which case five 

 only will be reckoned as belonging to the lumbar series. The 

 odontoid process of the atlas is wide, flat, and hollowed above, as 

 in the Ruminants. The bodies of the cervical vertebras are elon- 

 gated, strongly keeled, and markedly opisthoccelous, or concave 

 behind and convex in front. Their neural laminae are very broad, 

 the spines almost obsolete, except in the seventh, and the trans- 

 verse processes not largely developed. In the trunk vertebrae the 

 opisthoccelous character of the centrum gradually diminishes. The 

 spinous processes of the anterior thoracic region are high and com- 

 pressed. To these is attached the powerful elastic ligament, 

 ligamentum nuchce, or "pax wax," which passing forwards in the 

 middle line of the neck above the neural arches of the cervical ver- 

 tebrae, to which it is also connected, is attached to the occiput and 

 supports the weight of the head. The transverse processes of the 

 lumbar vertebrae are long, flattened, and project horizontally out- 

 wards or slightly forwards from the arch. The metapophyses are 

 moderately developed, and there are no anapophyses. The caudal 

 vertebras, except those quite at the base, are slender and cylindrical, 

 without processes and without chevron-bones beneath. The ribs 

 are eighteen or nineteen in number on each side, flattened, and 

 united to the sternum by short, stout, tolerably well ossified sternal 

 ribs. The sternum consists of six pieces ; the anterior or pre- 

 sternum being extremely compressed, and projecting forwards like 

 the prow of a boat. The segments which follow gradually widen, 

 and the hinder part of the sternum is broad and flat. 



As in all other Ungulates, there are no clavicles. The scapula 



