POLYODONTIDiE. — XX. 33 



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

 acter? 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. (ydvos, splendor, from the enam- 

 elled scales.) 



Order VII. SELACHOSTOMI. 



This order contains but one family. (creXaxos. shark or other 

 cartilaginous fish; ord/xa, mouth.) 



Family XX. POLYODONTID^E. (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; jzills 4£; no pseudobranchia; ; 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 ; I), posterior ; tail heterocercal, the lower lobe 

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

 air-bladder large, cellular ; stomach ca?cal, the pyloric c:eca 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 line and numerous; caudal fulcra many, small. 



1'olyodon, 29. 



29. POLYODON (Lacepede) Bloch & Schneider. 

 (ttoXvs , many ; 68d>v, tooth.) 



39. P. spathula (Walbaum). Paddle-Fish. Spoon-Bill. 



Duck-Billed Cat. Olivaceous; opercular flap in adidt reaching 

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

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

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



Order VIII. GLAXIOST03II. 



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

 fish ; a-Topa, mouth.) 



Family XXI. ACIPENSERID^E- (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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