274 PALEONTOLOGY 



above are supported by the premaxillary bones : the first, 

 second, and fourth of the lower jaw are the longest. 



The eight or nine posterior teeth are nearly conical, the 

 rest are sub-compressed antero-posteriorly, and present a 

 trenchant edge on the right and left side, between which a 

 few faint longitudinal ridges traverse the basal part of the 

 enamelled crown (fig. 80). 



The position of the opposite sharp ridges, and the direction 

 of the flat sides of the crown, are reversed in the extinct 

 crocodile {Croc. cultridensY which in other respects most nearly 

 resembles the gavial in the form of the teeth. 



In most of the extinct species of Crocodilians the teeth are 

 characterized by more numerous and strongly developed longi- 

 tudinal ridges upon the enamelled crown, than in the recent 

 species ; and they are commonly longer, more slender, and 

 sharp-pointed. But in one of the crocodiles with sub-biconcave 

 vertebras (Goniopliolis crassidcns), from the Wealden formation 

 and Purbeck limestone, the teeth have crowns which are as 

 round and as thick in proportion to their length as in the 

 recent crocodiles or alligators. 



The more ancient crocodiles, from the Oolite and Lias, 

 called Stcneosauri and Telcosavri, had jaws like those of the 

 modern gavials, but sometimes longer and more attenuated, 

 and armed with more numerous, equal and slender teeth, 

 adapted for the capture of fishes, which appear to have been 

 the only other vertebrate animals existing at those periods in 

 numbers sufficient to yield subsistence to carnivorous marine 

 Saurians. 



In all the Trfcosauri the teeth arc more slender, Less com- 

 pressed, and sharper pointed than in the gavial ; they are 

 slightly recurved, and the enamelled crown is traversed by 

 more numerous and better defined ridges --two of which, on 

 opposite sides of the crown, are larger and more elevated than 

 tlie rest. The fang is smooth, cylindrical, and always exca- 



