POLYODONTIM. XX. 33 



guisli the living Ganoids from all Teleosts, but none of these char- 

 acters can be verified in the extinct forms. It seems to us better 

 not to regard the Ganoids as a separate class or subclass, but to 

 unite them with the Teleosts. (yavos, splendor, from the enam- 

 elled scales.) 



ORDER VII. SELACHOSTOMI. 



This order contains but one family. (oreXa^off, shark or other 

 cartilaginous fish; ord/na, mouth.) 



FAMILY XX. POLYODONTID^EJ. (THE PADDLE- 

 FISHES.) 



Body fusiform, the skin mostly smooth ; snout prolonged in a 

 flat, spatulate blade, which overhangs the broad, terminal mouth ; 

 the "spatula " with a reticulated framework ; teeth very numerous, 

 minute, disappearing with age ; opercle rudimentary, its skin pro- 

 duced in a long flap ; gills 4 ; no pseudobranchias ; gill rakers very 

 long, in two rows, separated by membrane; gill membranes con- 

 nected, free from isthmus; one branchiostegal ; spiracles present. 

 C. fin with fulcra ; D. posterior ; tail heterocercal, the lower lobe 

 nearly as long as the upper; sides of tail with rhombic plates; 

 air-bladder large, cellular ; stomach caacal, the pyloric casca form- 

 ing a branching, leaf-like organ. Singular fishes, feeding on mud 

 and minute organisms which they stir up on the bottom with the 

 long oar-like snout. Two species, Psephurus gladius of rivers of 

 China, and the following. 



a. Gill rakers very fine and numerous; caudal fulcra many, small. 



POLYODON, 29. 



29. POLYODON (Lacepede) Bloch & Schneider. 

 (TroXus, many ; 68&v, tooth.) 



39. P. spathula (Walbaum). PADDLE-FISH. SPOON-BILL. 

 DUCK-BILLED CAT. Olivaceous ; opercular flap in adult reaching 

 V. ; head with flap and spatula more than half length. D. 55, 

 A. 57, V. 45. L. 6 feet. Miss, valley; common in larger streams. 

 (P. folium Lac.) (Lat. spatula.) 



ORDER VIII. GLANIOSTOMI. 



This order contains only the family of Sturgeons. (yAai/iy, cat- 

 fish ; oro/za, mouth.) 



FAMILY XXI. ACIPENSERID^l. (THE STURGEONS.) 



Body elongate, fusiform, with five rows of bony keeled shields, 

 the skin between these rows with small or minute plates; snout 

 produced ; mouth inferior, protractile, toothless ; four barbels in a 

 cross-row before mouth ; gills 4 ; an accessory opercular gill ; no 



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