88 THEORY OF THE EARTH. _ 



rous animals ; they have, therefore, no acromion 

 or clavicle, and their shoulder-blades are narrow. 

 Having also no occasion to turn their fore-arm, 

 their radius is united to the ulna by ossification, 

 or at least articulated by a ginglimus or hinge- 

 joint, and not by arthrodia or ball and socket, to 

 the humerus. Their food being herbaceous, will 

 require teeth furnished with flat surfaces, for bruis- 

 ing seeds and plants. The crown of the teeth 

 must also be unequal, and, for this purpose, must 

 be composed of parts alternately consisting of bone 

 and of enamel. Teeth of this structure neces- 

 sarily require horizontal motions to enable them 

 to triturate the food ; and hence the condyle of 

 the jaw cannot be so strictly confined within its 

 articulating cavity as in the carnivorous animals, 

 but must be flattened, and thus correspond with 

 a more or less flattened surface of the temporal 

 bones. Further, the temporal fossa, which will 

 only have a small muscle to contain, will be nar- 

 rower, and not so shallow, as that of carnivorous 

 animals. All these circumstances are deducible 

 from each other, according to their greater or less 

 generality, and in such a manner, that some of 

 them are essential and exclusively peculiar to 

 hoofed animals, while others, although equally 

 necessary in these animals, are not entirely pecu- 

 liar to them, but may occur in other animals also, 

 where the rest of the conditions will permit their 

 existence. 



