Page:Natural History, Fishes.djvu/315

Rh there are usually two dorsals, two large pectorals, two ventrals with (in the males) two large appendages at their inner edge, an anal, and a caudal of two unequal lobes, as before described in the Sturgeons. The body and fins are covered with a hard leathery skin, almost always rough

to the touch if the hand be passed from the tail upwards. This roughness arises from the presence of small angular spiculæ of crystalline appearance, imbedded in the skin, and fits the skin and fins of various species to be used for polishing cabinet-work. In some species the skin is studded with curved spines.