Of the immense numbers of these fishes that exist in the tropical seas, some idea may be formed from the fact that in a single harbour (that of Kingston), on the coast of Jamaica, from one hundred to one hundred and fifty thousand are destroyed annually. These are principally young ones, which are taken in numbers at every haul of the seine. On our own coast Sharks (not, however, of this species) are very numerous. Mr. Couch says of the Picked Dog-fish (Spinax acanthias), "I have heard of twenty thousand taken in a seine at one time." These also were young ones. But they have doubtless many enemies; and few of the young which swarm in such incredible numbers, live to attain adult age and dimensions.
4. Spinacina. The Dog-fishes. These are readily recognised by the spiracles or air-holes which are placed, one on each temple, just behind the eye. The dorsals in several of the genera are each preceded by a strong spine. This also is a numerous group, and includes most of the British Sharks.
5. Squatinina. The Angel-fishes. This is the form by which the Sharks merge into the Family of the Rays. It is much depressed, with the head broad, flat, and rounded; the eyes are placed on the summit of the head, and the mouth at the extremity, while the gill-apertures are beneath. The pectorals are enormous, as are the ventrals, giving to the fish that rhomboidal outline common to the Skates: the dorsals also are placed far back. This subdivision is represented by a British species, Squatina angelorum, of large size and great voracity, and held in no esteem.
