ON BRITISH FOSSIL REPTILES. 7l 



bony armour, and repeating a structure which is highly characteristic of the 

 large bony and enamelled scales of the extinct ganoid genera of fishes, Dape- 

 dius and Tetragonolepis. Many of the scutes are 6 inches in length and 2^ 

 inches in breadth. 



The exterior surface of the scute is impressed, as in the Teleosaur, by 

 numerous deep, round, or angular pits, from two to four lines in diameter, 

 and with intervals of about two lines, formed by convex reticularly disposed 

 ridges of the bone ; but a larger proportion of the anterior part of the scute 

 is overlapped by the contiguous scute than in the Teleosaur, and this part is 

 smooth, and thinner than the rest of the scute. The whole of the inner sur- 

 face of the scute is smooth ; but on a close inspection it is seen to be every- 

 where impressed by fine straight lines, decussating each other at nearly right 

 angles, and indicating the structure of the corium in which the scutes were 

 imbedded. From the size and strength of these dermal bones, their degree 

 of imbrication, and the structui-e for interlocking, we may conclude that the 

 Swanage Crocodilian was better mailed than even the extinct Teleosaur, which 

 Cuvier regarded as " I'espece la mieux cuirassee de tout le genre." 



If the detached vertebrse from the Wealden, communicated by Dr. Mantell 

 to Cuvier, belonged to the obtuse-toothed species and not to the Sitchosaurus 

 cultridens, it would then have been known that the Swanage Crocodile de- 

 viated, like the Teleosaur and most extinct Crocodilian species of the secondary 

 strata, from the Crocodiles, Alligators, and Gavials of the present day, in having 

 both articular extremities of the body of the vertebra slightly concave. 



Cuvier* has associated the obtuse teeth with this form of vertebra without 

 hesitation ; but it must be admitted that there was room for some doubt, two 

 distinct species, at least, having been indicated by the fossil teeth. 



In the slabs between which the remains of the Swanage Crocodile are di- 

 vided, the vertebrai were unfortunately all at right angles to their plane, and are 

 fractured across the middle, one extremity being buried in one of the halves 

 of the slab, and the other in the opposite half. By permission of the Trus- 

 tees of the British Museum, and the kind aid of the distinguished Mineralo- 

 gist at the head of the Geological Department, this doubt has been solved 

 since the reading of the present Report at Plymouth. The limestone has 

 been carefully removed from the two extremities of the same vertebra, and 

 both are equally but slightly concave. 



In. Lines. 



The length of the body of the vertebra examined was . . 1 10 



Vertical diameter of the articular extremity 1 9 



Transverse diameter of the articular extremity .... 1 8 



Ditto of middle of the body Oil 



Ditto of entire vertebra, including the transverse processes 10 



Height of entire vertebra, including spinous process . . 4 4; 



From the lower part of the centrum to the base of the \ cy n 



transverse process J 



There is a small irregular medullary cavity in the centre of the body of 

 the vertebra : this cavity is much more capacious in the Poikilopleuron : the 

 exterior compact crust of the body of the vertebra is about two lines in thick- 

 ness. The suture which joins the neural arch to the centrum is conspicuous ; 

 it forms an ascending angle or curve at its middle part. The body of the 



* " Les vertubves sont un peu concaves aux deux extremites, ce qui les rapproche du Croco- 

 dile de Caen et du deuxieme de ceiLX de Honfleur; cepcndant je les trouve plus voisines du 

 premier pour rensemblc. Les dents sont pour la plupart plus obtiises nicnie que dans nos 

 Crocodiles vulgaircs, et ressembleut en ce point a la seconde du Jiua que j'ai decrite ci- 

 dessus." — L. c, p. 323. 



