ORDER SAURIA. 99 



raised into a ridge or crest on their middle. There 

 is a crest with strong indentations in the tail, double 

 at its base. The scales of the belly are square, slen- 

 der, and smooth ; the nostrils open at the end of the 

 muzzle by two small crescented clefts, closed by val- 

 vules, and proceed by a long narrow canal, pierced 

 in the palatines and the sphenoid, into the bottom of 

 the hinder part of the mouth. 



The lower jaw being prolonged behind the cra- 

 nium, gives an appearance of mobility to the upper; 

 and the ancients believed that this was the case ; but 

 it moves only with the entire head. 



Their external ear may be closed at will by two 

 fleshy lips. Their eye has three lids. Under the 

 throat are two small holes, orifices of glands, in which 

 a musky sort of pommade is secreted. 



The vertebrae of the neck rest one upon the other 

 by little false ribs, which render lateral motion diffi- 

 cult. Accordingly, we find that these animals have 

 some trouble in changing their direction, and are 

 easily escaped from by turning : they are the only 

 saurians which are destitute of clavicular bones ; but 

 the coracoi'd bones are attached to the sternum, as in 

 all the rest of the order. Besides the true and false 

 ribs, there are some which protect the abdomen 

 without ascending as far as the spine, and which 

 appear to be produced by the ossification of the 

 tendinous inscriptions of the straight muscles. 



Their lungs do not sink into the abdomen, like 



H 2 



