298 FOSSIL REPTILES. 



down to the lowest of the batracian reptiles, is generally the 

 cartilage of the right side, passing over that of the left. 



There is always a small hole for the vessels pierced in the 

 neck of the bone, between its apophyses and the glenoid facet. 



The cartilaginous semi-circle just mentioned, acquires hard- 

 ness and consistence with age, but not so much as the other 

 bones. It is hardened by the accumulation of small calcare- 

 ous grains, like the bones of chondropterygian fishes. 



The omoplate forms the other portion of the glenoid facet. 

 In the midst, or at about one-third of its length, the osseous part 

 suddenly terminates, and is continued by a cartilaginous por- 

 tion. This frequently becomes hardened, and then the omo- 

 plate is divided constantly into two bones. 



The clavicle rests on one side against the slender bone of the 

 sternum, or its lateral branch, and often it touches the opposite 

 clavicle. On the other side it rests against the anterior edge 

 of the omoplate, either on its osseous or its cartilaginous por- 

 tion, which often puts forth a tubercle, or little crest, to re- 

 ceive it. Sometimes an apophysis proceeds from the osseous 

 omoplate which sustains the body of the clavicle, and has 

 some slight resemblance to an acromion, which, however, is 

 better represented by the tubercle of the cartilaginous part. 



This is the general structure of these parts in all lizards. 

 The differences in the various sub-genera are of small im- 

 portance. 



The pelvis of the lizards is composed of three bones, which, 

 as in viviparous quadrupeds, concur to the formation of the 

 cotyloid cavity. The ilium takes the upper part ; the pubis 

 and ischium unite each to its opposite in the lower middle line, 

 but the pubis does not join the ischium, and the two ovalary 

 foramina are separated only by a ligament. There is a fora- 

 men in the neck of the pubis, of tolerable size, and a pointed 

 process from its anterior edge, which curves below and ex- 

 ternally. 



The humerus has great analogies of form with that of the 



