Jordan and Everrnann. — Fishes of North America, 103 



anal somewhat behind it, similar; tail heterocercal, the lower caudal lobe 

 developed; the upper lobe of the tail covered with rhomboid scales. Air 

 bladder large, simple, connected with the oesophagus. Pseudobrauchite 

 small or obsolete. Stomach without blind sac; rectum with a spiral valve; 

 pancreas divided into pyloric appendages. 



Large fishes of the seas and fresh waters of northern regions, feeding on 

 small animals and plants sucked in through the tube-like month. Most 

 of the species are migratory, like the salmon, which are found in the same 

 waters. Genera 2; species about 20; although more than 5 times that 

 number have been described. The American species especially have been 

 unduly multiplied, particularly by Auguste Dumdril, who has found up- 

 wards of 40 of them in the museum at Paris. But 6 American species are 

 known to us, and wo doubt if any more exist. The changes with age are 

 considerable; the 8nout,in particular, becomes much shorter and less acute, 

 and the roughness of the scales is greatly diminished ; the ventral shields 

 sometimes disappear altogether. The number of plates, although one of 

 the best specific characters, is subject to considerable variation. (Acipen- 

 8ERID.E, Giinther, Cat., viil, 332-345.) 



a. Spiracles present; snout subconic; rows of bony shields distinct throughout; the tail not 

 depressed nor mailed; gill rakers lanceolate. Acipenser, 64. 



aa. Spiracles obsolete; snout subspatulate; rows of bouy shields confluent behind the dorsal so 

 that the depressed tail is completely mailed; gill rakero small, fan-shaped, ending in 

 3 or 4 points. Scaphirhynciius, 65. 



64. ACIPENSER, Linnaeus. 



(Sturgeons.) 



Acipefn^er, (Artedi), Linn;eus, Syst. Nat., Ed. x, 1758, 237, (s/iirio). 



Sturio, Rafinesque, Indice Itt. Sicil., 41, 1810, {slurio). 



Slerlelux, Rafinesque, Ich. Oh., 79, 1820, {serotinus). 



Dinediin, Rafinesque, /. c, 82, (Iriuicatus). 



Huso, Brandt & Ratzeburo, Medizin. Zool., 11, 3, 1833, {huso). 



Slerletus, Brandt & Ratzeburg, L c , 3, {riifheuns). 



Helop.i, Brandt & Ratzeburg, I. c, 3,{steUahts). 



Lioniscus, Fitzinger & IIeckel, Ann. Wien. Mus., 370, 1836, (glaber). 



Antacens, Brandt, Bull. Ac. Sci. Petersb., v, 138, 1865, {schypa). 



Snout subconical, more or less depressed below the level of the fore- 

 head. A small spiracle over the eye. Caudal peduncle moderately long, 

 deeper than broad, the rows of bony bucklers distinct to the base of the 

 caudal fin. Tail not produced into a filament, its tip surrounded by the 

 caudal rays. Gill rakers small, narrowed or lanceolate. Pseudobranchia^ 

 present. Species numerous in all northern rivers and seas. (acijH'tiser, 

 sturgeon.) 



n. Plates between ventrals and anal small, in 2 rows of 4 to 8; space between dorsal and lateral 



shields with stellate plates of moderate size, in about 5 rows, interspersed with smaller 



ones. Dorsal shields about 12; lateral about 45; ventral about 2. D. 47; A. 29. Color 



plain grayish. transmontanus, 145. 



aa. Plates between ventrals and anal large, in 1 row, or in 2 rows anteriorly and 1 posteriorly, 



of 1 to 4 plates caeli. 



b. Space between dorsal and lateral shields with stellate plates of rather largo size, in 5 



to 10 series; last doi-sal shield of moderate size, more thau }^ length of one before it. 



