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).

Yale's Trunk Fish (Ostracion Yalei).