FISHES 



31 



and the Mississippi Valley and northwards; abundant; the largest fish 

 in these regions. 



A. transmontanus Richardson. White sturgeon. Length 1,500 

 mm.; head 4; depth 7; weight 125 lbs.; record length 4,000 mm.; record 

 weight 1,000 lbs.; color dark gray; dorsal plates 11; laterals 44; ventrals 

 10 to 12; rays of dorsal fin 45; anal 28: Pacific Ocean from Alaska to 

 Monterey, ascending the streams, in which it may remain throughout 

 the year. 



A. medirostris Ayres. Green sturgeon. Length 2,000 mm.; head 

 4.25; depth 7.5; weight 350 lbs.; color olive green, with a midventral 

 stripe and one on each side above the ventral plates; dorsal plates*io; 

 laterals 26 to 30; ventrals 7 to 10; rays of dorsal fin 35; anal 28: Pacific 

 Ocean from San Francisco northwards, ascending the streams; not used 

 for food. 



2. Scaphirhynchus Heckel. Snout broad and shovel-shaped; spir- 

 acles absent; caudal peduncle slender, long and flattened, and covered 



Fig. 14. — Acipenser ruhicundiis {from Jordan tf Evermann). 



with bony plates; pseudobranchise absent; tail ending in a long filament; 

 ribs 10 or 11: i species. 



S. platorhynchus (Rafinesque). Shovel-nosed sturgeon. Length 

 1,200 mm.; head 4; depth 8; weight 9 lbs.; color pale olive; dorsal plates 

 17 or 18; laterals 41 to 46; ventrals 11 to 13; rays of dorsal fin 32; anal 

 20: upper and middle Mississippi Valley; common. 



3. Parascaphirhynchus Forbes and Richardson. Like Scaphir- 

 hyncJius but with the belly naked; ribs 20 or 21: i species. 



P. alhus F. and R. White sturgeon. Length 1,000 mm.; weight 

 5 lbs.; color very hght gray or white; dorsal plates 16 to 19; laterals 

 41 to 47; ventrals 10 to 13; rays of dorsal fin 35 to 43; anal 20 to 23: 

 Mississippi and Missouri Rivers; rare. 



Order 3. Holostei. — The bony ganoids. Skeleton bony; branch- 

 iostegals present; mouth terminal and with teeth; body covered with 

 ganoid or cycloid scales; tail heterocercal; air bladder cellular and lung- 

 like and connected by a sort of glottis with the oesophagus: 2 families, 

 with 5 American species. 



