346 POLYODONTID^. 



Fam. 2. POLYODONTID^. 



Spatularisc, Midler, Abhandl. Ak. Wiss. Berlin, 1844, p, 147. 



Body naked, or with minute stellate ossifications. 

 Mouth lateral, very wide ; jaws with minute teeth. 

 Nostrils double. Barbels none. Caudal fin with 

 fulcra. Dorsal and anal fins approximate to the 

 caudal, which is heterocercal. Four gills and a half; 

 no opercular gill or pseudobranchia. 



Mississippi and Yantsekiang. 



One genus only. 



1. POLYODON. 



Polyodon, Lacep. i. p. 402. 

 Spatularia, Shinv, Zool. v. p. 362. 

 Plauirostra, Lesueur. 



Body c4ongate, rather compressed, naked or with minute stellate 

 ossifications. The snout is produced into an exceedingly long, 

 shovel-like process, thin and flexible on the sides. Mouth lateral, 

 behind the rostral projection, exceedingly wide. The maxillary and 

 lower jaw are armed with a series or narrow band of minute teeth. 

 A band of similar teeth on the palatine bones. No tongue. Nostrils 

 double, immediately in front of the eye. Fins as in Acijtenser, the 

 lower caudal lobe being nearly as long and broad as the upper. 

 Spiracles present. Gill-cover terminating in a very long tapering 

 tiap ; gill-membranes continuous below the throat, and free from the 

 isthmus. One broad branchiostegal. Four gills and a half; each 

 branchial arch with a double series of very long setiform gill-rakers, 

 the two series being divided by a broad membrane (P. folium). No 

 opercular gill ; no pseudobranchia. Air-bladder cellular, not bifid, 

 communicating with the dorsal wall of the oesophagus. Stomach 

 caecal. Pyloric appendages in the form of a short, broad, leaf-like 

 organ, with four or five larger divisions, each being subdivided. 

 Hectura with a fully developed spiral valve. 



Mississippi and Yantsekiang. 



1. Polyodon folium. 



Mauduit, in Rozier, Journ. Phys. iv. p. 384, pi. 2. 



Polyodou folium, Lacep. i. p. 403; Mitch. Sillim. Juuni. xii. 1827, 



p. 201 ; Kirtlcmd, Bost. Journ. N(d. Hist. iv. p. 21, pi. 2. fig. 1. 

 Spatularia reticulata, Shmv, Zool. v. p. 3()2, pi. 150. 

 Platirostrii odcnlula, Lesueur, Journ. Ac. i\at. Sc. Philud. i. p. 223 ; 



Kirtluiul, I. c. \. p. 22, pi. 7. fig. 2. 

 Plauirostra spatula, Owen, Ostcol. Catal. i. p. 8.'{. 



