54 FISHES OF NORTH CAROLINA. 



Series GANOIDEA. The Ganoid Fishes. 



The ganoids are primitive iishes, mostly fossils, with only a few living 



representatives. The group is not sharply defined, but is chiefly characterized 



by a more or less complete armor covering the body, by numerous valves in the 



arterial bulb which forms a part of the heart, and by a spiral valve in the lower 



part of the intestine. The American species are few in number, and fall into 



four families which are easily distinguished. The salient characters of each are 



given in the following key in greater detail than in the preceding general key to 



the true fishes : 



Key to the families of ganoid fishes. 



i. Skeleton chiefly cartilaginous; skin either armed with bony plates or naked; branchiostogals 

 single or absent; spiracles present. 

 a. Snout prolonged into a long, paddle-shaped blade; no barbels; sides of tail with small bony 



plates; mouth broad, terminal; air-bladder cellular Polyodontid^. 



aa. Snout prolonged, but not flat and paddle-like; barbels present on under side of snout; 

 body imperfectly covered with large bony plates; mouth circular, inferior; air-bladder 



a simple sac Acipenserid^. 



a. Skeleton bony; body completely covered with small bony scales; branchiostegals few or 

 numerous; spiracles absent; air-bladder cellular. 

 b. Both jaws more or less prolonged, toothed, the upper jaw projecting; nostrils near end 

 of upper jaw; no barbels; dorsal fin short, high, placed posteriorly, opposite anal; 



branchiostegals 3 Lepisosteid^. 



bh. Jaws not produced; nostrils widely separated; a barbel at anterior nostril; dorsal 

 fin very long, low, beginning nearly opposite pectorals; branchiostegals 10 to 12. 



Amiatid^. 



Order SELACHOSTOMI. The Shark-mouthed Ganoids. 



Family POLYODONTIDiE. The Paddle-fishes. 



Body elongate, slightly compressed; snout a greatly prolonged flattened blade, 

 widest toward the rounded tip; skin nearly smooth, with rhombic bony plates on 

 side of tail; mouth wide, tongue absent, teeth in jaws and on palatines numerous, 

 small, and disappearing with age; operculum rudimentary, pseudobranchiae 

 absent; a single branchiostegal; lateral line present, continuous; spiracles present; 

 nostrils double, located at base of blade; air-bladder cellular; intestine with a 

 spiral valve; dorsal and anal fins soft-rayed, placed far backward; pectorals 

 thoracic, ventrals abdominal. Only two genera known, one Chinese, the other 

 American. 



Genus POLYODON Lac^pfede. Paddle-fishes. 



This genus, which includes a single species, has numerous very long, slender 

 gill-rakers, in a double series on each gill-arch; and caudal fin forked, its bent 

 portion with 12 to 20 fulcral plates, in addition to the foregoing family characters. 

 {Polyodon, many-toothed.) 



25. POLYODON SPATHULA (Walbaum). 

 Paddle-fish; Spoon-billed Cat-fish. 



Squalus spathula Walbaum, Artedi Genera Piscium, 522, 1792. 

 Polyodon folium, Cope, 18706, 492; French Broad River near Asheville. 

 Polyodon spathula, Jordan & Evermann, 1896, 101, pi. 20, figs. 43, 43a. 



