34(i roLroDONxiD^. 



Fam. 2. POLYODONTIDvE. 



Spatularise, Milller, Ahhandl. Ak. Wiss. Berlin, 1844, p. 147. 



Body naked, or with minute stellate ossifications. 

 Mouth lateral, very AAdde ; 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 Yantsekiaiig. 



One genus onhj. 



1. POLYODON. 



Polyodon, Lacep. i. p. 402. 

 Spatularia, Shaiv, Zool. v. p. 362. 

 Planirostra, Lesueur. 



Body elongate, rather compressed, naked or with minute stelhite 

 ossifications. The snout is produced into an exceedingly long, 

 shovel-like process, thin and tiexible 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 baud of similar teeth on the palatine bones. No tongue. Nostrils 

 double, immediately iu front of the eye. Fins as in Acij>enser, the 

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

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

 Hap ; 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 giU-rakers, 

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

 opercular giU ; no pseudobranchia. Air-bladder cellulai', not bifid, 

 communicating with the dorsal wall of the oesophagus. Stomach 

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

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

 Kectum with a fully developed spiral valve. 



Mississippi and Yantsekiang. 



1. Polyodon folium. 



3Iaudiiit, in liozicr, Journ. I'hys. iv. p. 384, pi. 2. 



Polyodon folium, Lacep. i. p. 403; Mitch. Sillim. Juurn. xii. 1827, 



p. 201 ; Kirtland, Boat. Journ. Nat. Hist. iv. p. 21, pi. 2. lig. 1. 

 Spatularia reticulata, Shaic, Zool. v. p. 362, pi. lo6. 

 Platirostra edeutula, Lesueur, Jcurn. Ac. Nut. ksc. Philad. i. p. 223 ; 



Kirtland, I. c. v. p. 22, pi. 7. i]g. 2. 

 Planirostra spatula, Owen, Osteal. Catal. i. p. 83. 



