THE TEETH OF FISHES. 223 



tical with that of the actual teeth of another ray, the 

 Myliobates ; the other that they are socketed, a manner of 

 implantation not at all common amongst the teeth of fishes ; 

 and yet another, that they grow from persistent pulps, also 

 unusual in fishes. 



Broadly speaking, the teeth of the Kays (skates) differ 

 from those of typical sharks by being individually blunter, 

 and being more closely set so that they form something ap- 

 proaching to a continuous pavement over the jaws, with but 

 little interspace left between the teeth. 



FIG. 96 ( 



The dentigerous surface of the jaw is very much rounded, 

 and in some is completely encased under a pavement of teeth. 



C 1 ) Upper and lower jaw of Myliobates. At a, the mosaic pavement 

 formed by the broad flattened plates which constitute its teeth is seen, 

 these being the oldest teeth which are about to be shed off in consequence 

 of the rotation of the whole sheet of mucous membrane over the surface 

 of the jaws. The letter 6 indicates the under surface of one of the plates, 

 which is seen to be finely fluted on its edge. 



