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 mavillary 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, poimted 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 vertebre 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 
