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THE COMMON STURGEON OF HOKKAIDO. 



BY 



K. Otaki. 



During the months of Jul)- and August young Sturgeons of about 4-5 cm long 

 and, later in the season, larger and full grown examples of 170 cm in length are 

 common in the fish market of Sapporo. The}- are chiefly caught in the large rivers of 

 Ishikari and Tesliio of Hokkaido, and they are of one kind. Of these there are in 

 the stuffed of the College of Agriculture, the Tohoku Imperial Univ ersit>-, three large 

 stuffed specimens of 170-180 cm in length and many other small ones of different 

 sizes preserved in formalin. One of the large specimens is female, which is a speci- 

 ally good example being not deformed as it is often the case in stuffed specimens. 



The head and cheeks bony and rough; operculum rugose; snout not ver\- short 

 and rather rounded ; the skin between the series of the scutes above and below, is 

 profused with irregular small ossifications, the larger ones being stellate in the 

 anterior dorsal portion. Head 4 or 3^, depth 7|-8 times in the bod\", but the head in 

 the young is generally larger and contained 3 times in the body; eyes nearly median 

 in the head of the full grown specimens, while in the young the preorbital region is a 

 little longer ; barbels simple and cylindrical, and they are nearer to the eye than to 

 the tip of the snout ; the transverse aperture of mouth is equal to the distance from 

 the upper lip to the barbels. The dorsal scutes lo-ii; the lateral scutes 33-34 

 on the right. 31-53 on the left ; the ventral scutes 7-9 on each side. Dorsal fin 

 III32-III37 ; the anal IIl24-\'l20. The origin of the anal fin is below ^-| 

 posterior of the dorsal fin and it is also preceded by 2 or 3 bony tubercles. The 

 vertical fins in the older fish are preceded by 3 or 4 short tubercles instead of 

 fulcrum. The scutes are radiating and not verj" large, each with a prominent ridge 

 and distant. There are three oblong plates behind the dorsal fin, the middle one 

 being larger; there are also 3 or 4 plates behind the anal vent and one or two behind 

 [Tran?. Sip. Xat. lis . Soc. Vol., Fart I-IT. 1907.- 



