Jordan and F.vennan?i. — Fishes of Nort/i America. 101 



rysium distinct; basihyals and superior ceratohyal not ossified; inter- 

 clavicles present ; maxillaries obsolete : branchihyalscaitilaginons. This 

 order contains but one family, P()LYODONTID.e. (ffe/la^^^r/, shark ; ar'ufin, 

 mouth.) 



Family XXX. POLYODONTID^. 



(The Paddle-fisiies.) 

 r5ody fusiform, little compressed, covered with mostly smooth skin. 

 Snout prolonged, expanded into a thin Hat blade, the inner portion formed 

 by the produced nasal bones, the outer portion with a reticulate bony 

 framework, the whole son\ewhat flexible. Mouth broad, terminal, but 

 overhung by the spatulate snout, its border formed by the premaxillaries, 

 the maxillaries being obsolete; jaws with many fine deciduous teeth; 

 similar teeth on palatines ; no tongue. Spiracles present. Operculum 

 rudimentary, its skin produced behind into a long acute flap ; no pseudo- 

 branchiie, or opercular gill; gills 4|; gill rakers long, in a double series 

 on each arch, the series divided by a broad membrane; gill membranes 

 considerably connected, free from the isthmus; a single broad bi-anchios- 

 tcgal. No barbels. Nostrils double at base of blade. Lateral line con- 

 tinuous, 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. Pectorals moderate, placed low ; ventrals abdom- 

 inal, many-rayed. Airbladder cellular, not bifid ; pyloric ccecainthe form 

 of a short, broad, branching, leaf-like organ ; intestine with a spiral valve. 

 Two species known — Polyodon spathula and Psephurus gladius; singular 

 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. (Poi.yodontid.e, Giinther, Cat., viii, 346-347.) 



a. Gill rakors very fine and uumoixms; caudal fulcra small and numerous. Polyodon, 63. 



63. POLYODON, Lac^pede. 



(Paddle-fishes.) 



Pohjndntt, LAcfipiiDE, Hist. Nat. Pois,^., i, 402, 1798, (fenille); French name only. 



rohjodnn, Bi.ocH & Schneider, Syst. Ichth., 457, 1801, {folium). 



Sp„liil«ria, SiiAW, Gen. Zoiil., v, 302, 1804, (relkulala). 



rialirnatra, Le t^UEun, Jour. Ac. Nat. Sci. Pliila., i, 1817, 227, {edenlula). 



Phtnlrosira, Rafinesque, Ich. Oh., 83, 1820, (edenlula). 



Pioceros, Rafinesque, Ich. Oh., 87, 1820, (mneH^aiiis). 



Gill rakers exceedingly numerous, very slender ; spatula broad. Caudal 

 fulcra 13 to 20 in number, of moderate size. Characters otherwise those 

 of the family. Rivers of the middle United States. (toAic, many ; o(5oi'j-, 

 tooth.) 



144. POLYODON SPATHULA, (Walbaum). 



(Paddle-fish; Spoon-bili, Cat; Duck-bii.l Cat; Spade-fish.) 



Opercular flap very long, nearly reaching to ventrals ; premaxillary 

 extending far behind the small eye. Skin smooth, or nearly so, except the 



