344 GANOID FISHES. 



/. POLYODON, Lacepede. DUCK-BILLED CATS. 



= /Spatularia, Shaw. 

 = Planirostra, LeSueur. 



1. P. folium, Lacepede. DUCK-BILLED CAT. SPOON- 

 BILLED STURGEON. Snout nearly ^ of length; opercular 

 flap reaching much beyond pectorals; fins all more or 

 less falcate; color gray; D. 55 to 60; A. 56; length 5 

 feet or more. Mississippi and its larger tributaries, 

 abundant. A singular fish, bearing considerable resem- 

 blance to a Shark. 



ORDER FF.-OHO1TDROSTEL 



(The Cartilaginous Ganoids.) 

 This order is equivalent to the family AcipenseridcB. 



FAMILY CXV. ACIPENSERID.E. 



(The Sturgeons.) 



Body elongate, sub-cylindrical, with five longitudinal 

 rows of bony shields, the lower sometimes deciduous; 

 snout produced; mouth entirely inferior, transverse, 

 protractile, toothless; four barbels in a row under snout 

 in front of mouth; vertical fins with fulcra; caudal hete- 

 rocercal; dorsal and anal far back. No branchiostegals; 

 air bladder large, not cellular; stomach not ccecal, with 

 pyloric appendages; intestines with spiral valve. Dis- 

 tribution same as that of Salmo. Fresh waters of 

 northern regions, some species marine and entering rivers. 

 Genera two; species twenty ((runther), eighty or more 

 (August Dume'riV). Perhaps in no group has the making 

 of nominal species been carried to a greater extent than 

 in this. 



