176 



THE ANATOMY OF ^'ERTEBRATED ANIMALS. 



The anterior caudal vertebriB have no transverse processes, 

 but possess ribs which may not become anchjlosed with the 

 centra. Thus the tail and the neck are the onlv re2:ions of 

 the spinal column of a Chelonian which are flexible. 



In the skulls of the Ghelonia all the bones, except the 

 mandible and the hjoidean arch, are immovably united to- 

 gei.her. 



In the occipital segment of the adult, the supra-occipital 

 is united with the epiotic, but the ex-occipital usually remains 

 perfectly distinct from the opisthotic. The basisphenoid is 

 large and distinct. The alisphenoidal region remains unossi- 

 fied ; but the large parietals send down a prolongation on 

 each side, w^hich plays the part of an alisphenoid. Neither 

 the presphenoid nor the orbitosphenoids are represented by 



P'lo. 66. — Long-itudinal sections of the skull of the Tm-tlo. The upper fi;^ire represents the 

 entire skull with the outline of the brain in situ ; the lower gives a larger view of tho 

 inner face of the bones of the p^terior moiety of the skull. 



