242 



ZK 



COMPARATIVE ANATOMY 



/ .3 2 ' 3, ^ 



- -RP 



ZK 



JIF 



c.c 



B ^O c 



FIG. 193, A. TOOTH OF FROG, AND 193, B, Salamandra atra. 



ZK, crown ; ZS, base ; RF, circular furrow ; S, apex, covered with enamel ; 

 PH, pulp-cavity ; M, maxilla. 



FIG. 193, C. TRANSVERSE SECTION THROUGH PORTION OF A TOOTH OF A LABY- 

 RINTHODONT (Mastodonsaurux). (After J. Storrie. ) 



C.c, central pulp-cavity ; 1, inflections of the enamel, surrounded by dentine, 

 which reach the centre (c.c) ; 2, half-length inflections between 1 ; 3, short 

 inflections between 1 and 2. 



resembling the incisors of Mammals, and working together like 

 scissors; in some Fishes they give rise to a definite pavement, 

 are rounded in form, and serve to crush the food. They may, 



