16 FOSSIL REPTILES OF DORSET. 



Trias in incisors, canines, and molars. The proportionate shortness 

 of the head from the orbit to the snout exceeds that of any living 

 Crocodile; the alveolar portion of the maxilla bulges out; the 

 vertebrae are concave at both ends and very shallow. The molar- 

 teeth, unlike the incisors and canines, are not in separate sockets. 

 Some of the back molars are laterally compressed and lamellated ; 

 those of the inferior-jaw are lodged in a common depression of the 

 outer bone like Lacertilia. From the Feather-bed, Middle Purbecks, 

 Swanage. 



GENUS POLYPTYCHODON, Owen. 



POLYPTYCHODON CONTINUUS, Owen. 



Sir R. Owen says of this genus " In collecting materials 

 for my report on British Fossil Reptiles I soon found that 

 among the evidences of that class in the Cretaceous deposits of 

 England, a large species of Saurian was indicated by thick conical 

 teeth, having the general character of the teeth of the crocodile, 

 but distinguished by the more regular circular transverse section of 

 the crown, the absence of two opposite larger ridges and the 

 presence of numerous close-set, narrow, longitudinal ridges, a 

 comparatively small number only of the ridges extending to near 

 the apex. The general aspect of the teeth at first sight resembles 

 the great Sauroid fish, Hypsodon, whose teeth are also found in 

 the Chalk, but may be distinguished from it by the greater solidity 

 of the crown, which, in Hypsodon and other predatory fish, have a 

 large cavity, and are more rapidly shed and renewed than in the 

 Crocodilian Reptiles. The animal to which the teeth belonged 

 must have been of enormous size, quite equal to Cetiosaurus. The 

 absence of medullary cavities in the large bones shews that it was 

 not a Deinosaur. It was marine in habits ; the metatarsals, from 

 their form and proportions, testify to its being neither Cetacean nor 

 Enaliosaurian. Found in the Lower Greensand at Frome Vauchurch. 

 CROCODILIAN JAW, Newton. 



From the Coralline rocks of Weymouth, consisting of the 



Monograph Foss. Rep. Pal. Soc., Cretaceous Formations, Part I., 1851, 

 p. 47. 



