HERBIVORA 



381 



homologues of the lower canines, reduced in size and altered 

 in shape, so as to form the outer teeth (c) of a bent row of 

 incisors terminating the lower jaw. The back teeth (Ji) 

 instead of being trenchant, 

 have broad and flat crowns, 

 roughened with hard ridges, 

 opposing each other with a 

 grinding action, like mill- 

 stones. The lower jaw is long 

 and slender ; it articulates to 

 the skull by a flat condyle (d), 

 admitting of rotatory move- 

 ments upon a flattened arti- 

 cular surface on the skull, and 

 limiting the extent of opening 

 and shutting the mouth. The 

 coronoid process (r) is very 

 slender, and the fossa which 

 marks the size of the temporal 

 muscle (t) is correspondingly 

 small. The zygomatic arch 

 (o) is short and feeble, and its 

 span is narrow ; it is almost 

 straight, or with a slight bend 

 downwards. The parts of the 

 skull (pterygoid plates) which 

 afford attachment to the rotat- 

 ing muscles of the jaw, and 

 the (angular) part (/) of the 



jaw into which they are in- Pafcontological chwacters of a Ruminant 



serted, are of great extent. (Bos). 



The ox masticates grass with great efficiency ; it inflicts no 

 injury to other animals with its teeth. The horns are its 

 weapons, and they are chiefly defensive. 



