A SYNOPSIS OF THE STURGEONS (ACIPENSERID^) OF 



JAPAN. 



B}^ David Starr Jordan and John Otterbein Snyder, 



Of Stanford University, California. 



Two .species of sturgeon {Acipenser) are known to inhabit the waters 

 of Japan. In addition to these, a few other species have been recorded 

 from rivers of Manchuria and of China. These may be found to enter 

 streams of Saghalin or of Hokkaido. 



The following is an analysis of the species known in Japanese waters: 



Genus ACIPENSER Linnseus. 



a. Dorsal fin very long, of more than 60 rays; anal rays about 40; dorsal plates 11; 

 lateral plates 32; skin between series of scales nearly smooth; anal below 



posterior part of dorsal ; snout rather short kihichii 



aa. Dorsal fin moderate, of 35 to 40 rays; anal rays about 30; dorsal plates 7 or 8, 

 lateral plates 34; skin between series of shields with small stellate plates; 

 snout rather sharp mikadoi 



ACIPENSER KIKUCHII Jordan and Snyder. 



Acipenser Hkuchii Jordan and Snyder, Journ. Coll. Sci. Tokyo, XV, 1901, p. 

 302, pi. XV, figs. 1, 2; Misaki, Sagami Bay. 



Head, 4i in length; depth, 7. Snout, 2f in head. Dorsal plates, 11; 

 lateral, 32; ventral, 11. Dorsal raj^s. III, 63; anal, III, 37. Head 

 longitudinally concave above. Snout shortish, rather sharp. Dorsal 

 plates large, rugose, without distinct spines; lateral plates each with 

 a spine in front, those below smooth. A large rugose plate behind 

 dorsal and behind anal. No bonj^ plates on body except the live 

 series, and a few small ones between the large anterior ones of dorsal 

 series, the skin between the rows of plates soft and smooth. Opercle 

 rugose; cheeks with fine stellate prickles. Height of dorsal, 2^ times 

 in head; insertion of anal below posterior part of dorsal; pectoral, If 

 in head; upper lobe of caudal, 1^ times head. 



Of this species but one specimen is known. This is a mounted exam- 

 ple, 1.80 meters long, in the Museum of the Imperial University of 

 I Tokyo. It was taken in a net in the open sea off Misaki, in Sagami 



Proceedings U. S. National Museum, Vol. XXX— No. 1455. 



397 



