SAURIAN REPTILES. 459 



structure in the batrachia. The caudal ver- 

 tebrae are always numerous, and the tail is com- 

 pressed vertically, which is the form most 

 favourable for progression in water. They are 

 remarkable also for having inferior spinous pro- 

 cesses attached to the bodies by cartilages ; a 

 structure analogous to that which we have seen 

 in fishes. 



The number of ribs differs in different species 

 of Sauria : they are always articulated to the ex- 

 tremities of the transverse processes of the ver- 

 tebrae, of which they appear to be continuations. 

 Processes of this description also occur in the 

 neck, attached to the transverse processes of the 

 cervical vertebrae ; and these have been regarded 

 as cervical ribs. Their presence are impedi- 

 ments to the flexions of the neck ; whence 

 arises the difficulty which the crocodile appears 

 to have in bending the neck while turning 

 round upon the animal he is pursuing. In the 

 thorax, the ribs are connected with a broad 

 sternum ; but there are other ribs, both before 

 and behind, which have no such termination, 

 and therefore bear the name of false ribs. 



The pelvis consists chiefly of the iliac bones, 

 which, as in the batrachia, pass backwards to 

 form the articular cavity for the thigh bone. 

 Two small and slender bones extend forwards 

 from the pubic bones, on the under side of the 



