April, 1910. Fishes of Chicago — Meek and Hildebraxd. 235 



Polyodon spathula (Walbaum). Paddle-fish; Spoonbill Cat. 



Head (from tip of snout to end of opercular flap) 1.5 to 1.7 ; depth 

 4 to 4.8 (without snout); A. 60. Body fusiform, little compressed; 

 skin smooth; snout broad, its greatest width 3.4 to 4.3 in its length; 

 opercle with long flap; its tip reaching ventrals (adults) or nearly 

 to front of dorsal (young) ; gill rakers long and slender, in a double 

 series on each arch; no scales; tip of caudal peduncle and sides of 

 upper caudal lobe with small elongate rhombic plates. 



Color pale to dusky, or bluish olive. 



Length about 6 to 8 feet. 



This fish lives in the larger rivers and in bayous. It is not native 

 to Lake Michigan, but is reported to have been taken there. 



Order Chondrostei. 



The Sturgeons. 



Skeleton chiefly cartilaginous; vertebrae simple and acentrous, 

 the notochord persistent; ventral fins abdominal; opercular series 

 represented by an opercle and interopercle; maxillary present; air 

 bladder simple; connected by a duct with the oesophagus. 



Family Aeipenserldap. 



The Sturgeons. , 



Body elongate, armed with 5 longitudinal rows of bony plates, 

 head covered with bony plates ; ventral fins abdominal ; fins without 

 spines ; gills 4 ; an accessory opercular gill ; nostrils double, in front 

 of eye; optic nerves forming a chiasma; mouth inferior, protractile, 

 with thickened papillose Hps; 4 barbels in front of mouth; stomach 

 without pyloric coeca; intestine with spiral valve; arterial bulb with 

 several pairs of valves. 



Genus Acipeiiser Linnaeus. 



Snout conical; caudal peduncle short, roundish, and not entirely 

 covered with bony plates; spiracles and pseudobranchs present; gill- 

 rakers lance-shaped; air bladder well developed, not cellular. 



