THE TEETH OP FISHES. 



217 



are not as yet fully calcified and firmly attached to the 

 gum. 



In Lamna, which may be taken as fairly illustrative, the 

 teeth are arranged round the jaws in concentric rows with 

 great regularity, the teeth of the successive rows correspond- 

 ing in position to the teeth of older rows, and not, as is the 

 case in some other sharks, to their interspaces. They are 



FIG. 93 f 1 ). 



attached by being embedded in a densely fibrous gum, which 

 closely embraces their bifurcated bases ; and this dense gum, 

 carrying with it the teeth, slides bodily upwards over the 

 inner face of the jaw, and outwards over its border, beyond 



0) Transverse section of lower jaw of a Dog-fish, a. Oral epithelium. 

 b. Oral epithelium passing on to flap. c. Protecting flap of mucous mem- 

 brane (thecal fold), d. Youngest dentine pulp. e. Youngest enamel 

 organ. /. Tooth about to be shed. g. Calcined crust of jaw. 



