Mud Fish (amia, Linn.), a genus of American ganoids, found in the fresh waters of the United States. After it had been referred by ichthyologists to cyprinoid, salmonoid, and clupeoid fishes, Vogt discovered it to be a ganoid, having found in the muscular arterial trunk two oblique rows of five or six valves each and a spiral intestinal valve. Müller considers it the living representative of a ganoid family, like the fossil megalurus, leptolepis, and their congeners. The body is long and flexible, with a bony vertebral column; there are no spiny plates on the anterior border of the fins as in the gar fish, nor a series of separate dorsal fins as in polypterus; the mouth is trout-like, except in the absence of lingual teeth; there are two nasal cirri; the head is flat, and the bones under the very thin skin are sculptured plates; the large sublingual bone is naked and furrowed, the gill openings large, and the bran-chiostegal rays broad and flat, 11 or 12; tongue thick and fleshy; behind the conical teeth of the jaws are flat pavement-like ones; the scales are horny rather than osseous, flexible and rounded, yet presenting bone corpuscles of the same form and character as lepidostevs and other ganoids; the ventral fins are median, the single dorsal long, and the anal short; the caudal comes further forward above than below, rounded, giving an indication of the heterocercal tail.
The larger air bladder is cellular and lung-like, communicating with the oesophagus; no pancreatic caeca; ova dropping into abdominal cavity. Of about ten species, the best known is the western mud fish (A. occidentalis, De Kay), from 1½ to 3 ft. long; the back of the bead is bluish black, the sides often obscurelv spotted with olive, white below, and with a black spot at the upper edge of the caudal. It is found in the great northern lakes, south to Carolina, and west to the Mississippi: it is the bowfin of Lake Champlain, the dog fish of Lake Erie, and the marsh fish of the Canadians; it feeds on crawfish and other crustaceans, and is sometimes eaten by the Indians. This may include several species.
Western Mud Fish (Amia occidentalis).