242 



DENTAL SYSTEM OF FISHES. 



of this kind. Conical teeth, as close-set and sharp-pointed 

 as the villiforme teeth, but of larger size, are called "rasp- 

 teeth" {denies raduliformes^ Lat. ; dents en rape^oven cardes^ 

 Fr.) ; the pike preseots such teeth on the back part of the 

 vomer. The teeth of the sheat-fish (Silurus glanis) present 



Fig. 60. 



JAWS AND TEETH OF THE STING-RAY {Afyllobates). 



all the gradations between the villiform and raduliforni 

 types. Setiform teeth are common in the fishes thence 

 called Chaitodonts ; in the genus Githarinai they bifurcate 

 at their free extremities ; in the genus Platax they end 

 there in three diverging points, and the cone here merges 

 into the long and slender cylinder. Sometimes the cone 

 is compressed into a slender trenchant blade : and this 

 may be pointed and recurved, as in the murcena; or 

 barbed, as in trichiurus and some other Scomberoides ; or 

 it may be bent upon itself, like a tenter-hook, as in the 

 fishes thence called Ooniodonts. In the bonito may be 

 perceived a progressive thickening of the base of the 

 conical teeth; and this being combined in other predatory 

 fishes with increased size and recurved direction, they 

 then resemble the laniary or canine teeth of carnivorous 

 quadrupeds, as we see in the large teeth of the pike (Fig. 

 59), in the lophius, and in certain sharks. 



