Page:Natural History, Fishes.djvu/331

Rh are here greatly extended in breadth in proportion to their length, giving to the fish somewhat of the outline of a bat or a butterfly, dilated to gigantic dimensions. The anterior half of the head is free, and the eyes are placed at the margin of its summit. The teeth are arranged like broad flat paving stones, of regular forms: the tail is still more lengthened and attenuated than in the last sub-family, and is furnished with a serrated spine; it has a small dorsal near its base. Two species of this group are British, though very rare; one of these is the Cephaloptera, already mentioned as attaining colossal proportions, and displaying a fierce voracity in the tropical seas.

In this the most numerous genus of the Family, and the only one of any value to man, the disk is rhomboidal, greatly flattened; the tail is moderately slender, generally armed with rows of small spines; there is no notched spear, but two small dorsals near the tip are present, and sometimes the vestige of a caudal; the teeth are flattened, small, arranged in quincunx, the central ones becoming lengthened and pointed with age. The head and neck cannot be externally distinguished from the body, being included on the sides by the fore-part of the pectorals. The body is in general beset with sharp points, or spinous tubercles, sometimes small and few as in the Skate (Raia batis, .); sometimes large and numerous as in the Thornback (R. clavata).