2 8 Memoir Sears Foundation for Marine Research 



Key to Genera^ 



I a. Spiracles present; snout subconical; tail not depressed or completely mailed; gill 

 rakers lanceolate. 

 2 a. Gill membranes joined to isthmus. Jdpenser hmna.eus 1758, below. 



2 b. Gill membranes free from isthmus and broadly connected between themselves. 



Huso Brandt 1869. 



Basins of the Adriatic, Black, 

 and Caspian seas, and the Far 

 East (Amur River). 

 lb. Spiracles absent; snout shovel-shaped, depressed above; tail depressed and mailed; 

 gill rakers fan-shaped. 



3 a. Caudal peduncle completely mailed, and long, with tip of anal fin remote 



from caudal base; barbels fringed. Scaphirhynchus Heckel 1835. 



Mississippi River Basin.^" 

 3 b. Caudal peduncle incompletely mailed, and short, with tip of anal fin reaching 

 almost to caudal base; barbels smooth. P seudoscaphirhynchus Nikolski 1900. 



Turkistan (Basin of the Aral Sea). 



Genus Acipenser Linnaeus 1758 



Acipenser Linnaeus, Syst. Nat., ed. 10, 1758: 237; type species, A.sturio Linnaeus. Atlantic Ocean, along 

 European coast. 



Generic Synonyms: 



Ichthocolla GeofFroy, Descr. de 719 Plantes, etc., 1767: 399 (presumably A. huso L.). 



Sterleta Giildenstadt, Nov. Com. Acad. Petropol., 16, 1772: 533 {A.rulhenus h). 



Sturio Rafinesque, Indice Ittiol. Sicil., 1810: 41 (S/urio vulgaris Rafinesque = A.sturio L.). 



Sterlctus Rafinesque, Ichthyol. Ohiensis, 1820: 80 {A. serotinus Rafinesque = A.fuhescens Rafinesque). 



Helops Brandt and Ratzeburg, Medizinische ZooL, 2, 1833: 3, 349 {A. stellatus Pallas = A.helops Pallas). 



Sterletus Brandt and Ratzeburg, Medizinische Zool., 2, 1833: 349 {A.ruthenus L.). 



Sturio Miiller, Vergleich. Anat. Myxinoiden, 1835: 77 {A.sturio L.). 



Antaceus Heckel and Fitzinger, Ann. Wien. Mus., J, 1836: 293 {^A. sckypa Eichwald). 



Lioniscus Heckel and Fitzinger, Ann. Wien. Mus., J, 1836: 370 {A. glabra Fitzinger). 



Sterletus Bonaparte, Cat. Metod., 1845: 21 {A.vultharius L.). 



Ellops, Gistel, Naturg. Thierreichs, 9, 1 848 {A. helops Pallas). 



Schipa Brandt, Bull. Acad. Sci. Petersb., 7, 1850, 113 {A.schypa Eichwald). 



Characters. Gill membranes joined to isthmus. Spiracles present. Snout sub- 

 conical. Tail depressed and completely mailed. Gill rakers lanceolate. Characters 

 otherwise those of the family. 



9. Since Sturgeons change with age in such features as head proportions and characteristics of scutes, the preparation 

 of keys apphcable to both young and adult stages has involved selection of those characters that are most constant 

 throughout life. 

 10. According to Dr. R. D. Suttkus (personal communication, July 9, 1957), a specimen of S. album, 532 mm FL 

 and weighing 553 g, was taken in the brackish water of Vermilion Bay at Cypremont Point, Louisiana, on May 

 10, 1954, by Lester Boudreaux while trawling for penaeid shrimp. 



