CROCODHJA 



-_>75 



vated at the base. The teeth of the Steneosauri, or extinct 

 crocodiles with long and slender jaws, and with vertebras sub- 

 concave at both extremities, but with subterminal nostrils, 

 differ from those of the Tdeosawri in being somewhat thicker 

 in proportion to their length, and larger in proportion to the 

 jaws. 



The teeth of both the existing and extinct crocodilian 

 reptiles consist of a body of compact dentine, forming a crown 

 covered by a coat of enamel, and a root invested by a moder- 

 ately thick layer of cement. The root slightly enlarges or 

 maintains the same breadth to its base (fig. 80, a), which is 

 deeply excavated by a conical pulp-cavity extending into the 

 crown, and is commonly either perforated or notched at its 

 concave or inner side. 



The tooth-germ c (figs. 80 and 81) is developed from the 

 membrane covering the angle 

 between the floor and the inner 

 wall of the socket. It becomes, 

 in this situation, completely 

 enveloped by its capsule, and 

 partially calcified, before the 

 young tooth penetrates the in- 

 terior of the pulp-cavity of its 

 predecessor. 



The matrix of the young 

 growing tooth affects, by its 

 pressure, the inner wall of the 

 socket, as shown in figs. 80 and 

 81, and forms for itself a shallow 

 recess ; at the same time it 

 attacks the side of the base of the contained tooth : then, 

 gaming a more extensive attachment by its basis and increased 

 size, it penetrates the large pulp-cavity of the previously 

 formed tooth either by a circular or semicircular perforation. 



Fig. 81. 



Section of jaw with tooth of the 

 Alligator. 



