Trunk Fish, the name of the plectognathous fishes of the genus ostracion (Linn.), derived from the bony case in which their soft parts are enclosed; they are also called coffer fishes. The head is prolonged into a snout, at the end of which is the mouth, with fleshy lips, and armed with a series of distinct teeth, 10 or 12 in each jaw, received into sockets, somewhat like the human incisors; body covered by bony plates, large, quadrangular or hexagonal, encasing the animal in an inflexible bony armor; tail enclosed in a bony tube, this and the pectoral fins being the only movable parts; even the vertebrae are usually immovable; eyes large and prominent; dorsal single, far back, small, and entirely soft; pelvic bones and ventrals absent; body three- or four-sided, with linear branchial openings, bordered by a fleshy edge within which are the gill covers. They have very little flesh, and some are believed to be poisonous; the stomach is membranous and very large; the liver is also large, often yielding a considerable quantity of oil; some are armed with spines on the head and body; they are generally small, and found in the tropics.
There are a few species on the coast of the United States, arranged by De Kay in his genus lactophrys, having a triangular body, with strong spines, directed backward, in front of the anal fin, and the orbits usually spinous. Yale's trunk fish (0. [L.] Yalei, Storer), on the coast of Massachusetts and New York, is 14 in. long, with two abdominal spines. There are also species in the East Indies.
Yale's Trunk Fish (Ostracion Yalei).