Dog Fish, a cartilaginous plagiostome, of the family squalidoe or sharks, and the genus acanthias (Risso), of the class selachians of Agassiz. This genus is characterized by two dorsal fins with a strong spine before each; the first dorsal is behind the line of pectorals, the second between the ventral and caudal spaces; no anal fin; temporal orifices large; skin rough in one direction, the scales heart-shaped with a central spine directed backward; teeth in several rows, sharp and cutting, with the points directed backward and outward. The common dog fish (A. Americanus, Storer) has the upper part of the body of a slate color, deepest on the head and lightest on the sides, and white below; just under the anterior portion of the lateral line is a row of circular white spots, and a few similar ones are irregularly distributed on the back; the young are still more spotted; the length does not exceed 5 ft. The species is found from Davis strait to New Jersey. Dog fish in spring and autumn appear in large numbers in Massachusetts bay, and the residents of some towns on Cape Cod give up all other business at these times to fish for them; they are valuable for the oil from the livers, for the food of swine, and for the polishing property of their skin. The weight varies from 8 to 25 lbs.

They remain in shallow water three or four days, at which time they are easily caught with the hook; they feed on garbage, and may be called the scavengers of the sea. The young are brought forth alive, and are often seen swimming about with the yolk bag attached. In the British provinces they are dried, and in the winter given to pigs, which thrive well upon them; the refuse parts are used for manure. The dog fish (acanthias) of Europe is a different species; its flesh is eaten in Scotland. Along the east coast of England it is called the bone dog; it troubles the fishermen by cutting off their hooks; according to Mr. Couch, it bends itself into a bow for the purpose of using its spines, and then by a sudden motion causes them to spring asunder in opposite directions. Three species of scyllium (Cuv.), of a reddish brown color with numerous spots, are called dog fish in Europe. - There is another shark (mustelus canis, Mitch.), also viviparous, called dog fish. In this genus the teeth are blunt, forming a close pavement in each jaw; the first dorsal is in advance of the ventrals; there are no spines; the body is cylindrical and elongated, of a uniform slate color on the hack and sides, and dusky white below; the head is flat between the eyes.

This shark grows to a length of 5 ft., and is very common in Long Island sound, where it is taken in nets spread for other fish; from the form of the teeth it is probable that the food consists principally of Crustacea and mollusks; it is not common on the coast of Massachusetts, but is abundant on the shores of New Jersey, where it is very troublesome to the fishermen by stealing their baits and driving away other more edible species; its flesh, though occasionally eaten, is coarse, rank, and unpalatable. In Europe the species of this genus are often called hound fish; the M. Ioevis (Cuv.) is called the smooth hound from the softness of the skin, and ray-mouthed dog fish from the peculiar conformation of the teeth. - The dog fish of the great, lakes of North America is a soft-rayed bony fish, generally placed in the herring family, and the genus amia (Linn.).

Dog Fish (Acanthias Americana).

Dog Fish (Acanthias Americana).