DOG-FISH, a name applied to several species of the smaller sharks, and given in common with such names as hound and beagle, owing to the habit these fishes have of pursuing or hunting their prey in packs. The Small-spotted Dog-fish or Rough Hound (Scylliunt canieula) and theLarge-spotted or Nurse Hound (Scyllium catulus) are also known as ground-sharks. They keep near the sea bottom, feeding chiefly on the smaller fishes and Crustacea; and causing great annoyance to the fishermen by the readiness with which they take bait. They differ from the majority of sharks, and resemble the rays in being ovoviviparous. Their young are brought forth inclosed in semi-transparent horny cases, known on the British coasts as mermaids' purses, and these have tendril-like prolongations frona each of the four corners, by means of which they are moored to sea-weed or some other fixed object near the shore, until the young dog-fish is ready to make its exit. The larger of these species attains a length of 4 to 5 feet, the smaller rarely more than 30 inches. The Picked Dog-fish (Acanthias vulgaris) is pre-eminently the dog-fish. It is the smallest and most abundant of the British sharks, and occurs in the temperate seas of both northern and southern hemispheres. It rarely attains a length of two feet, the female, as in most sharks, being larger than the male. The body is round and tapering, the snout projects, and the mouth is placed far under. There are two dorsal fins, each of which is armed on its anterior edge with a sharp and slightly curved spine, hence its name " picked." In order to strike with these spines the fish first bends itself into a bow, and. by a quick motion causes them to spring asunder in opposite directions, seldom failing thus to strike the object aimed at. The dog-fish is exceedingly prolific, the female, according to Couch, producing young almost daily for 9 or 10 months in the year. These are not contaiued in egg cases, as in the ground-sharks, but are produced alive. It is gregarious, and is abundant at all seasons everywhere on the British coasts. Ili 1858 an enormous scull of dog-fish, many square miles in extent, appeared in the north of Scotland, when, says Couch, " they were to be found floating in myriads on the surface of every harbour." They are the special enemies of the fisherman, injuring his nets, removing the hooks from his lines, and spoiling his fish for the market by biting pieces out of them as they hang on his lines. Still greater injury is caused to the fisheries in the wholesale destruction of small fishes by this predacious species. They are, however, eaten, both fresh and salted, by fishermen, especily on the west coast of England.