3 6 Memoir Sears Foundation for Marine Research 



of shields only weakly developed; spleen short, not reaching farther back 

 than middle loop of small intestine. 



oxyrhynchus oxyrhynchus Mitchill 1814, p. 46. 

 3 b. In young specimens 50—70 cm long, head length 30— 34''/o of FL; bony 

 shields of dorsal rows rather square in shape, their longitudinal length 

 much shorter than their transverse width; carina on dorsal shields high, 

 typically with two strong hooks; dermal ossifications between dorsal and 

 lateral rows of shields strongly developed; spleen long, reaching much 

 farther back than middle loop of small intestine. 



oxyrhynchus desotoi Vladykov 1955, p. 56. 

 2 b. Mouth width over 62 "/o of interorbital ; average difference between TL and 

 FL less than i2"/o of FL; gill rakers 22—40; postdorsal and preanal shields 

 in a single row; viscera blackish, heavily pigmented. 



4a. Gill rakers 22-29 (^'^- 25-4)'> interorbital width 34— 40''/(, (av. 37'/o) 

 of hi; dorsal shields 8-13 (av. 10); lateral shields 25-32 (av. 28.3); 

 dorsal and lateral shields pale, contrasting with dark background; 

 length, so far as known, not over 100 cm. 



brevirostris LeSueur 18 18, below. 



4b. Gill rakers 25-40 (av. 33.1); interorbital width 2g-2S°lo (av. 32"/o) 



of hi; dorsal shields 9-17 (av. 13.4); lateral shields 29-42 (av. 35.4); 



dorsal and lateral shields brownish, of same color as background; 



length commonly over 100 cm. fulvescens Rafinesque 18 17, p. 41. 



I b. Species of the Pacific Seaboard. 



5a. Caudal peduncle short; tip of anal fin reaching or even extending beyond base 

 of lower lobe of caudal ; modified shield at beginning of dorsal fin rudimentary 

 or absent; 11 — 14 dorsal shields; 38—48 lateral shields; gill rakers 34—36; 

 viscera blackish, heavily pigmented. transmontanus Richardson 1836. 



Southern Alaska to California; enters salt water. 



5 b. Caudal peduncle long; tip of anal fin not reaching base of lower lobe of caudal ; 



a large modified shield at beginning of dorsal; 8— 1 1 dorsal shields; 23—31 



lateral shields; gill rakers 18—20; viscera pale, practically without pigment. 



medirostris Ayres 1854. 

 Southern Alaska to California; enters salt water. 



Acipenser brevirostris LeSueur 1 8 1 8 



Shortnose Sturgeon 



Figures 7, 8 



Study Material. A total of 109 specimens: 95, 450-900 mm TL, from the Hudson 

 River, New York;^'' i, presumably LeSueur's type, ANSP 16953;" i, from Dela- 



20. For age and localities of these specimens, see Greeley (J5; 89, 90). 



21. This specimen, originally No. 84, was described by Ryder [65: 236) and later by Fowler {33: 604, pi. 38, fig. i). 

 On June 23, 1949, the specimen (stuffed) measured 746 mm FL. 



