POLYODONTID^. — XX. 33 



guish 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.) J 



Order VII. SELACHOSTOMI. 



This order contains but one family. {creKaxos, shark or other 

 cartilaginous fish; aTOjia, mouth.) 



Family XX. POLYODONTID^. (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 4J; no pseudobranchite ; 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 heteroceroal, the lower lobe 

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

 air-bladder large, cellular ; stomach etecal, the pyloric cseca 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, Psephuncs gladius of rivers of 

 China, and the following, 

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



POLYODON, 29. 



29. POLYODON (Lace'pede) Bloch & Schneider. 

 (iroXuf, many ; obaiv, 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 'Luc.} (Lat. spatula.) 



Order VIII. GliAlSTIOSTOMI. 



This order contains only the family of Sturgeons. (yXavis, cat- 

 fish; o-To/io, mouth.) 



Family XXI. ACIPENSBRID^. (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 ; giUs 4 ; an accessory opercular gill ; no 



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