TEETH OE FISHES. 



371 



252 



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



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



so small, as well as numerous {denies (/run/formes), as to give a 



granvilated surflice to the part of the mouth 



to which they are attached (premaxillaries 



of Cossj/phus).^ A progressive increase of 



the transverse over the vertical diameter may 



be traced in the molar teeth of difixjrent 



fishes, and sometimes in those of the same 



individual, as in Lahrus, until the cylindrical 



form is exchanged ibr that of the depressed 



plate. Such dental j)lates {dentes luinelU- 



formes) may be found, not only circular, 



[)ut elliptical, oval, semilunar, sigmoid, ol)- 



long, or even square, hexagonal, pentagonal, 



or triangular ; and the frrindino- surface may 



present various and beautiful kinds of sculj)- 



turino-. 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 Sai-gus 



present the form of compressed plates, at 



least in the crown, and are dentes incisivi. 



Palatine bone ri 

 {Silai-as). 



Numerous wedjie- 



shaped dental plates {denies cuneati) are set vertically 



25t 



th 



253 



Handibulnrteolli. 

 liiau'iiillcd iJ'kitiu:!. \ 



Inferior uliaryii)joall)ono and teeth {LabrnsL v. 



upper pharyngeal bone of the Parrot-fish {Scants, 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 

 Fetalodus. Sometimes the incisive form of tooth is notched 

 in the middle of the cutting edge, as in Sarr/iis unimaculatus. 

 Sometimes the edge of the crown is trilobate {Aplodactijhis, 

 fio-. 256V Sometimes it is made nulnquelobate by a double 



I V. pi 45, fig, 1. 



11 15 2 



