THE COMMON DOG-FISH. 
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at tlie end, whereas in the former they are of a diamond-like form. The color of the Rock 
Dog-fish is brownish-gray above, without the red tinge of the little dog-fish, and covered rather 
sparingly with large patches of blackish-brown. Below it is whitish. The length of a fine 
specimen will sometimes be nearly a yard. 
Another species of Dog-fish, namely, the Black-mouthed Dog-fish, or the Eyed Dog- 
fish ( Pristidurus melanostomus ), is mentioned by Mr. Yarrell among the list of European 
^ fishes. It may be at once distinguished from either of the preceding species by its large snout, 
and a row of small, flat, and sharp-edged prickles, arranged in saw-like fashion on the upper 
rim of the tail fin. The generic title Pristidurus, or Saw-tail, is given to the fish in allusion 
to this peculiarity. 
Its color is light brown on the upper surface, sprinkled with spots, the smaller of which 
are scattered irregularly, and the larger arranged in four rows, two on each side. 
Its length is between two and three feet. 
The Dog-fish family includes six or more genera. The species number fifteen, — rather 
small sharks, chiefly of the Atlantic. The Black Dog-fishes are represented by one species, 
found lately off Gloucester, Massachusetts, by the naturalists of the United States Fishery 
Commission. It is a native in the Greenland seas. 
The Common Dog-fish, or Picked or Piked Dog-fish ; also called Bone-dog, from 
its potent bony weapons ; also Skittle-dog, and Hoe. Its range in the Atlantic is very 
wide, being very abundant on the shores of the Northern and Middle States. Its oil, from the 
liver, is prized, and it forms an important item of commerce among the fishermen. 
