Sharks' teeth, shells and bamboo were formerly generally used as cutting instruments for shaving and surgical operations.
Besides the commoner kinds of fishes, sharks, the torsk, opah and sunfish occur.
This elaborate type of scolex appears to be an adaptation to grasp the spiral intestinal valve of sharks and rays.
The manganese nodules afford the most ample proof of the prodigious period of time which has elapsed since the formation of the red clay began; the sharks' teeth and whales' ear-bones which serve as nuclei belong in some cases to extinct species or even to forms derived from those familiar in the fossils from the seas of the Tertiary period.
Many fish inhabited the Carboniferous seas and most of these were Elasmobranchs, sharks with crushing pavement teeth (Psammodus), adapted for grinding the shells of brachiopods, crustaceans, &c. Other sharks had piercing teeth (Cladoselache and Cladodus); some, the petalodonts, had peculiar cycloid cutting teeth.