OR OSSEOUS SYSTEM. 77 



Their teeth are organs of prehension, and not of mastica- 

 tion ; they are conical, slender, sharp, recurved, osseous 

 spines, covered with enamel, with very shallow alveoli, 

 placed along the upper and lower jaws, the intermaxillaries, 

 and the palatine bones. The upper jaw bones in the poi- 

 sonous snakes terminate abruptly in a round peduncle below 

 and before the orbits, which supports the tubular poison- 

 fang, and the small teeth which usually accompany it upon 

 each side of the head. 



The saurian reptiles have the skeleton more complete than 

 the serpents, as they possess a complex sternum, and 

 scapular apparatus, a fixed pelvis, together with atlantal and 

 sacral extremities ; but the transition from the one form is 

 very gradual from the serpents with the rudiments of pelvic 

 and scapular bones, to the bimanous and the biped lizards ; 

 and from these to the regular saurians with fore feet, and to 

 the more solid and complete forms of the skeleton presented 

 by the crocodilian reptiles. By the increased development 

 of all the processes of the vertebral column, we perceive 

 the preparation for more solidity in the articulations, and 

 more limited motions in that part of the skeleton, the loco- 

 motion is now to be effected by the arms and legs, and not 

 by the vertebral column, as in most of the lower vertebrata. 

 The large bones of the sauria present a coarse fibrous struc- 

 ture, contain a large proportion of animal matter, and have 

 a cancellated loose texture internally, where we find tubular 

 cavities in the birds and mammalia. The bodies of the ver- 

 tebrae, in the lacertine sauria, preserve the ball-and-socket 

 joint throughout the column ; but these parts of the verte- 

 brae are more compressed, and the articulations are more 

 oblique than in the serpents. From the necessity for sup- 

 porting the trunk upon the legs, the pelvis is united firmly 

 to a sacrum, consisting generally of only two enlarged ver- 

 tebrae. The bodies of the vertebrae are generally more 

 lengthened, and the articular processes more extended in 

 a longitudinal direction than in the serpents. There are two 

 concave surfaces of the bodies of the vertebrae, of the 

 gecko, as in fishes and tadpoles, and in the ichthyosaurus. 

 In the coccygeal vertebrae, besides the lengthened superior 

 spinous process, and the two transverse processes, there 

 are inferior spinous processes, which are interposed between 



