TEETH OF FISHES. 



371 



252 



surface, as to resemble a pavement, as in the pharyngeal bones of 

 the Wrasse or Rock-fish (Labrus, fig. 254) ; or they may be 

 so small, as well as numerous (denies graniformes}, as to give a 

 granulated surface to the part of the mouth 

 to which they are attached (premaxillaries 

 of Cossyphus). 1 A progressive increase of 

 the transverse over the vertical diameter may 

 be traced in the molar teeth of different 

 fishes, and sometimes in those of the same 

 individual, as in .Labrus, until the cylindrical 

 form is exchanged for that of the depressed 

 plate. Such dental plates (denies lamelli- 

 formes) may be found, not only circular, 

 but elliptical, oval, semilunar, sigmoid, ob- 

 long, or even square, hexagonal, pentagonal, 

 or triangular ; and the grinding surface may 

 present various and beautiful kinds of sculp- 

 turing. The broadest and thinnest lamelli- 

 form teeth are those that form the complex 

 grinding tubercle of the Diodon, fig. 257, 

 b. The front teeth of the Flounder and Sargus 

 present the form of compressed plates, at 



Palatine bone and teeth 

 (Silurus). v. 



least in the crown, and are denies incisivi. Numerous 



* 



shaped dental plates (denies cuneati) are set vertically in the 

 253 251 



Mandibnlar teeth,, 

 magnified (Platax). v. 



Inferior pharyngeal bone and teeth (Labrus). v. 



upper pharyngeal bone of the Parrot-fish (Scarus, fig. 255). 

 A thin lamella, slightly curved like a finger-nail, is the singular 

 form of tooth in an extinct genus of fishes, thence called 

 Petalodus. Sometimes the incisive form of tooth is notched 

 in the middle of the cutting edge, as in Sargus unimacitlatus. 

 Sometimes the edge of the crown is trilobate (Aplodactylus, 

 fig. 256). Sometimes it is made quinquelobate by a double 



1 v pi. 45, fig 1. 

 B B 2 



