Fossil Gavial J?om Neir Jersey. 161 



At c c are seen portions of two bones which are peculiar to 

 animals of this family, and were termed, by Adrian Camper, 

 opercular bones : they form the symphysis of the lower jaw, 

 and the dental bones repose against them, and go off posteri- 

 orly to form the branches of the lower maxillary. 



The total length of the fragment of the opercular bone of the 

 right side is 7*8. 



From the symphysis to the anterior termination of the same 

 bone is 6*2, 



Breadth of both operculars, just before the symphysis, is 2*4. 



Presumed breadth at symphysis 4. 



Breadth of jaw, at outer extremity 2*7. 



Thickness at same place 1*7. 



The upper surface of the opercular bones is smooth, and its 

 substance is very compact. The surface of the right dental 

 bone is likewise tolerably even ; but its side, and particularly 

 its inferior surface, has the same corroded and worm-eaten 

 appearance noticed in its companion on the left side. 



We are now furnished with sufficient data to pronounce that 

 the fragments under consideration are a portion of the lower 

 jaw of some species of animal belonging to a family of reptiles 

 which includes the crocodiles. 



In the last edition of that work which is destined to confer 

 immortality upon the name and labours of Cuvier, he has indi- 

 cated three groups, into which may be classed all the living 

 and fossil reptiles hitherto loosely designated under the name 

 of crocodile. It is not intended to give an analysis of his la- 

 bours, but it is necessary for our purposes to notice that he di- 

 vides them into three subdivisions, viz. Alligators, Crocodiles, 

 and Longirostres, or Gavials. The first includes the crocodiles 

 of America with semipalmate feet, and the fourth tooth on 

 each side of the low^er maxillary received into a depression of 

 the upper jaw. Four living species are enumerated. The 

 second subgenus, or crocodiles proper, distinguished by pal- 

 mate feet, and the fourth of the lower jaw passing by the upper, 



