Chap. 14 (12.) — Distribution of Aquatic Animals Into Various Species
The integuments of the aquatic animals are many in number. Some are covered with a hide and hair, as the sea-calf and hippopotamus, for instance; others again, with a hide only, as the dolphin; others again, with a shell,2303 as the turtle; others, with a coat as hard as a stone, like the oyster and other shell-fish; others, with a crust, such as the cray-fish; others, with a crust and spines, like the sea-urchin; others, with scales, as fishes in general; others, with a rough skin, as the squatina,2304 the skin of which is used for polishing wood and ivory; others, with a soft skin, like the muræna;2305 and others with none at all, like the polypus.2306