EQUIDA 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 vertebre, 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 vertebre are elon- 
gated, strongly keeled, and markedly opisthoccelous, or concave 
behind and convex in front. Their neural lamine are very broad, 
the spines almost obsolete, except in the seventh, and the trans- 
verse processes not largely developed. In the trunk vertebre 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 nuche, or “paxwax,” which passing forwards in the 
middle line of the neck above the neural arches of the cervical ver- 
tebrze, to which it is also connected, is attached to the occiput and 
supports the weight of the head. The transverse processes of the 
lumbar vertebre 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 
vertebre, 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 
