4 OPHIDIA. 



an extensible ligament which allows of their being drawn apart laterally; — 

 the bones of the upper jaw are also connected in the same way to the inter- 

 maxillary, and allow the same sort of motion. Even the palatine bones 

 participate in this general mobility and dilatability, which is still further 

 increased by the tympanal bone or pedicle of the lower jaw, which is always 

 suspended to another bone analogous to the mastoid process of the temporal, 

 and is attached to the cranium by muscles and ligaments. From this 

 structure, and from the mobility and distensibility of each of these bones, 

 it results that the mouth may be so widely opened as to receive an object 

 of greater dimensions than the animal itself. 



2. The mouth is of variable size, and is furnished with lips; and the upper and 



lower jaws, as well as the palatine arches in all, with only one exception, 

 (Oligodon,) are armed with teeth. These teeth are solid, of simple construc- 

 tion, and are always situated on the margins of the maxillary bones, and not 

 on the inner margin, as in some of the lizards. As the serpents do not 

 masticate their food, these teeth are organized for seizing and killing their 

 prey, or for retaining it; they are, accordingly, pointed and smooth, and 

 curved or arched backwards, to prevent its escape. 



3. The tongue is very long, slender, extensible, retractile within a sheath placed 



at the root, with the apex bifid, and terminating in two slender semi- 

 cartilaginous filaments. 



4. There are no movable eyelids, nor is there a tympanal membrane. 



5. The body is exceedingly elongated — destitute of a sternum or of any external 



members of locomotion; — though in some genera (Boa) there are concealed 

 rudiments of posterior limbs near the vent. The ribs and vertebra? make up 

 nearly the whole skeleton; the former surround a great portion of the 

 circumference of the body, and are only wanting at the tail; the latter are 

 curiously arranged, the body of one is articulated by a convex surface to a 



DSl 



