IV. No ventral fins whatever; vent remote from the head; gill-openings very wide, the gill-membranes not being united: Ammodytina.
The “Sand-eels” or “Launces” (Ammodytes) are extremely common on sandy shores of Europe and North America. They live in large shoals, rising as with one accord to the surface, or diving to the bottom, where they bury themselves with incredible rapidity in the sand. They are much sought after for bait by fishermen, who discover their presence on the surface by watching the action of Porpoises which feed on them. These Cetaceans, when they meet with a shoal, know how to keep it on the surface by diving below and swimming round it, thus destroying large numbers of them. The most common species on the British coast is the Lesser Sand-eel (A. tobianus); the Greater Sand-eel (A. lanceolatus), which attains to a length of eighteen inches; A. siculus, from the Mediterranean, scarcer in British seas. Two species live on the American coasts, A. americanus and A. dubius; one in California, A. personatus. Bleekeria from Madras is the second genus of this group.
Fig. 253.—Congrogadus subducens.
V. No ventral fins whatever; vent remote from the head; gill-openings of moderate width, the gill-membranes being united below the throat, not attached to the isthmus: Congrogadina.
Only two fishes belong to this group—Congrogadus from the Australian coasts, and Haliophis from the Red Sea.
Fourth Family—Macruridæ.
Body terminating in a long, compressed, tapering tail, covered with spiny, keeled, or striated scales. One short anterior dorsal; the second very long, continued to the end of the tail, and composed of very feeble rays; anal of an extent similar to that of the second dorsal; no caudal. Ventral fins thoracic or jugular, composed of several rays.
Fig. 254.—Scale of Macrurus trachyrhynchus.