in Ichthyology, a title given to all fishes whose muscles are supported by cartilages instead of bones; and comprehends the same genera of fish to which Linnæus has given the name of amphibia marines: but the word umphibia ought properly to be confined to such animals as inhabit both elements; and can live, without any inconvenience, for a considerable time, either on land or in water; such as tortoises, frogs, and several species of lizards; and among the quadrupeds, hippopotami, &c. &c.

Many of the cartilaginous fish are viviparous, being excluded from an egg, which is hatched within them. The egg consists of a white and yolk; and is lodged in a case formed of a thick tough substance, not unlike softened horn; such are the eggs of the ray and shark kinds. Some again differ in this respect, and are oviparous; such is the sturgeon, and others.

They breathe either through certain apertures beneath, as in the rays; on their sides, as in the sharks, &c.; or on the top of the head, as in the pipe-fish: for they have not covers to their gills like bony fish.