418 THE WONDERS OF GEOLOGY. Lect. IV. 



animal. The vertebra; are biconcave, and have a large 

 medullary cavity in the middle of the centrum of the bone, 

 which is often filled up with white calcareous spar. The 

 body of the vertebra is contracted in the middle, the 

 neural arch anchylosed with no trace of suture, and the 

 spinous process is remarkable for its backward inclination * 

 Raphiosaurus? Professor Owen states, in his report 

 on the British fossil reptiles, that no vertebrae of the true 

 crocodilian type, that is, with the anterior surface concave, 

 and the posterior face convex, have been found in strata 

 below the chalk. I have, however, discovered in the sand- 

 stone of Tilgate Forest, several small vertebrae of this 

 kind which closely resemble in their proportions those of 

 the 'small lizard of the chalk, the Rhaphiosaurus (ante, 

 p. 354). f 



* The remains of this reptile were first described by M Deslong- 

 champs, (under the name of Poecilopleuron,) from specimens discovered 

 in the Oolite near Calne, in Normandy. See British Association Report 

 for 1841, p. 84; Fossils of Tilgate Forest, PI. IX. ^.8, represents a 

 caudal vertebra. ^^ ^ ^ ^ ^ &m ^ th 



adult Gavial -The discovery of the Swanage crocodile induced 



* SSe a rigorous examination of the skeletons o the recent 



Gav Si in the museum of my friend Dr. Grant, of the London Umver- 



sHv w th the view of determining the affinities of the fossil remains. 



£ X course of my investigation I detected a peculiar conformation 



n Se first caudal or coccygeal vertebra of the recent gavial, which, 



strange to say, appears to have escaped the notice of previous oh- 



servers. The vertebra of the existing crocodilian family are mvanably 



concave in front, and convex behind ; but the first caudal (Ltgn. 100^ 



to the adult Gavial is doubly convex ; and the last sacral vertebra 



(2) concave posteriorly, to receive the anterior convexity or ball of 



the caudal. These peculiarities are shown in the annexed sketch. 



The last cervical vertebra in Turtles and Tortoises has a similar 



structure. In a very young Gavial in Dr. Grants collection the sura 



coccygeal surface, are as flat as in the vertebra, of mammaha : whj 



in the Crocodile and Alligator, of the same early period, Ihe coccygej 



ciebra is convex in front, a. in the adult gavial. This mcoluun*™ 



