230 



VERTEBRATA: REPTILIA OR REPTILES. 



blows from above, all the joints are made so that they can 

 best resist vertical pressure. And it may here be added 

 that, in accordance with this structure, there is little or no 

 natural upward and downward undulation of the body ; 



FIR. 2fi3. 



Ulack Snake, Bascamon constrictor, Baircl and Girard. 



but all the undulations are from side to side. The ribs 

 commence at the third vertebra from the head, and are 

 very numerous. They are movable, and aid greatly in 

 locomotion. 



The bones of the jaws and mouth, which in the higher 

 animals are more or less firmly united, are connected in 

 serpents by extensible ligaments only an arrangement by 

 which the mouth mav be distended so as to receive an 



