512 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



trils large, double, olfactory membrane with smooth central disk 

 surrounded by rosette of folds. Gills 4, also accessory opercular gill. 

 Branchial arches 5. Pseudobranchiae imperfect. Gill membranes 

 joined to isthmus. No branchiostegals. Air bladder large, joined 

 to esophagus with short pneumatic duct, sides spacious. Pancreas 

 divided into mushroomlike pyloric appendages. Spiral valve in 

 rectum. Five longitudinal rows of bony plates or bucklers, each 

 with median keel ending in spine, sometimes obsolete with age. Plates 

 as median dorsal, lateral and abdominal row each side, last some- 

 times deciduous. Skin between large plates rough with small irregu- 

 lar plates. Head covered with bony plates joined with sutures. Fin 

 rays slender, articulated. Vertical fins with fulcra. Dorsal fin pos- 

 terior. Anal similar and somewhat behind. Tail heterocercal, lower 

 lobe developed and upper covered with rhomboid scales. Pectorals 

 moderate, low. Ventrals many rayed, small, behind middle of body. 

 Large sluggish fishes, living in the seas and fresh waters of northern 

 countries. Their food is small or minute plant and animal life sucked 

 in through the tubelike mouth. Great variation individually and 

 with age has led to the description of many nominal forms. Genera, 

 four or five among living forms. 



Genus ACIPENSER Linnaeus 



Acipenser Linnaeus, Syst. Nat., ed. 10, vol. 1, p. 237, 1758, (Type, Acipenscr 



sturio Linnaeus, designated by Jordan and Copeland, Bull. Buffalo Soc. Nat. 



Hist,, vol, 3, p, 161, 1876.) 

 Accipenser Gouan, Hist. Pise, pp. 12, 13, 1770. (Type, Acipenser sturio 



Linnaeus. ) 

 IchthyocoUu Geoffroy, Descr. 719 plantes, p. 399, 1707. (Type, Acipenser huso 



Linnaeus. ) 

 Sterleta GiJiJ>ENSTADT, Nov. Com, Sei, Petropol., vol. 16, p. 533, 1772, (Species 



nonbinomial. Type, Acipenser ruthenus Linnaeus.) 

 Sturio Rai'INESQUe, Indice Itt, sicil., p. 41, 1810. (Type, Acipenser sturio Lin- 

 naeus, monotypic.) 

 Dinoctus Rafinesque, Amer. Monthly Mag. Grit, Rev,, vol, 3, p. 447, Oct. 1818. 



(Type, Dinoctus truncatus Rafinesque, monotypic. No description.) 

 Sterletus Rafinesque, Ichth, Ohiensis, p, 80, 1820, (Type, Accipenser serotinus 



Rafinesque=-4cl/)e«ser rubicundus Lesueur, designated by Jordan and Gilbert, 



Proc, Acad. Nat. Sci. Philadelphia, 1877, p. 87.) 

 Sterleda Bonaparte, Cat. Metod. Pesci Europei, p. 21, 1846. (Type, Acipenser 



ruthenus Linnaeus.) 

 Dinectus Rafinesque, Ichth. Ohiensis, p. 82, 1820. (Type, Dincctus truncatus 



Rafinesque= Acipe}?ser rubicundus Lesueur, monotypic.) 

 Ellops Minding, Lehrb. Naturg. Fische, p, 124, 1832. (Type, Acipenscr helops 



Pallas.) 

 Huso Brandt and Ratzebubg, Med. Zool., vol. 2, p. 4, 1833. (Type, Acipenser 



huso Linnaeus, tautotypic.) 

 Helops (not Fabricius, 1775, in Coleoptera) Mvller, Abh. Akad. Wiss. Berlin, 



1834, p. 73. (Type, Acipenser stellatus Pallas.) 



