25. POLYODONTID^E POLYODON. 83 



nous teeth. Similar teeth on the palatines. No tongue. Spiracles 

 present. Operculum rudimentary, its skin produced behind into a long, 

 acute Hap. No pseudobranchiai nor opercular gill. Gills 4J. Gill- 

 rakers long, in a double series on each arch, the series divided by a broad 

 membrane. Gill membranes considerably connected, free from the isth- 

 mus. A single broad brauehiostegal. No barbels. Nostrils double, at 

 base of blade. Lateral line continuous, its lower margin with short 

 branches. Dorsal fin well back, of soft rays only. Anal similar, rather 

 farther back. Tail heterocercal, the lower caudal lobe well developed, 

 so that the fin is nearly equally forked. Sides of the bent portion of the 

 tail armed with small rhombic plates. Caudal fin with fulcra. Pec- 

 torals moderate, placed low. Yentrals abdominal, many-rayed. Air- 

 bladder cellular, not bifid. Pyloric ccBca in the form of a short, broad, 

 branching, leaf-like organ. Intestine with a spiral valve. 



Two genera known, Polyodon and Psephurus, each of one species. Sin- 

 gular fishes, inhabiting the fresh waters of the United States and China. 

 They feed chiefly on mud and minute organisms contained in it, stirring 

 it up with the spatulate snout. 



(Polyodontidce Giintker, viii, 346-347.) 



* Gill-rakers very fine and numerous ; caudal fulcra small and numerous. 



POLYODON, 46. 



46. POLYODON Lac6pede. 



Paddle-fishes. 



(Spatularia Shaw : Platirostra Le Sueur.) 

 Lace"pede, Hist. Nat. Poiss. i, 402, 1798: type "Polyodon feuille" = P. folium Bloch.) 



Gill-rakers exceedingly numerous, very slender ; spatula broad. Cau- 

 dal fulcra 13 to 20 in number, of moderate size. Rivers of the United 



States. (rroAo?, many; odcbv, tooth.) 



73. P. spatliula (Walb.) J. & G. Paddle-fish ; Spoon-Mil Cat; Duck-Mil Cat. 



Color olivaceous, rather pale. Opercular flap very long, nearly reach- 

 ing to vcntrals. Spatula broad. Premaxillary extending far behind 

 the small eye. Skin smooth, or nearly so, except the rhombic plates on 

 the sides of the tail. Yentrals near the middle of the body ; dorsal 

 well behind them; anal mostly behind the dorsal, and somewhat 

 larger; these fins somewhat falcate. Fin-rays slender. Spiracle with 

 a minute barbel. Isthmus papillose in the young. Spatula 2 to 4 times 

 in length. Whole head, with opercular flap, more than half length. 

 Head, without spatula or flap, about 5. D. 50-60; A. 50-G5; V. 45- 



