8o i< IB.— it m it r- t- m. \'' m. ^ h ^^f; r ^ 



the anal fin. These latter are not unfrequently wanting in young specimens. The 

 upper caudal lobe t ,; times in the head. In young specimens of 25 cm-36 cm, the 

 posterior margin of the tail is straight; the pectral i^ times in the head. The 

 colour is greyish blue or light chestnut. 



Of the Japanese sturgeon two species. .^^7/r//r^r mikadoi, Hilgendorf, and A. 

 kil-uchii, Jordan and Snyder, in the Proc. U.S. National Museum, vol. XXX, pp. 

 3S^7-398' 1906, are recorded. Besides these a third species closely related to A. 

 mikadoi is A. güldenstädtii, Brandt of Russia. 



The common species of Hokkaido in c^uestion seem to be identical with A. 

 güldenstädtii in its rounded snout and small irregular stellate ossifications, while 

 the other data such as the number of scutes, the proportional length of snout and 

 depth in the body and the fin formula have their affinity to A. mikadoi. The 

 number of scutes in each series of five, and fin rays, taken as specific distinctions 

 are variable in different ages and even so in individuals of the same size. The fin rays 

 split up into two, four or sometimes into three, while the anterior rays often fuse 

 together to present two or three spines more in addition when the fish grows 

 older. In young specimens the dorsal scutes are horny with prominent claw-like 

 spines, the 4th being the largest, and decreasing in size both anteriorly and posterior- 

 ly, and in the lateral series a large portion of posterior scutes is simply a dermic 

 papillae. Snout in young specimens is short or shortish and bluntly pointed. Of 

 young specimens we notice that in some of them the snout is a little longer than 

 others and the scutes are lesser, while in others the snout is a little broader at its 

 base and shortish with blunt point. The aperture of the mouth is even with the 

 distance of the mouth and the barbels, and i^ times in the rostrum before the 

 barbels. This difference among the same species may possibly be a sexual one 

 which could not be determined at the time. I reserve the final determination 

 until a further examination can be made of both sexes in fresh fish. 



Another sturgeon, a single specimen contained in the museum, seems to be 

 c|uite a different fish, of which I shall hope to have another opportunity to describe, 

 when I have more specimens to compare with it. 



The tabular accouiits of the species are as follow : 



Note : — 

 (i) and (2}, the figures with the plus marks between show that the next figures are 

 the number of an unossified dermal papilla, and those with the same mark 

 before or after or the plus alone, show that tliere is present an imperfect 

 plate or two. 

 (3), the spines are indiscernible. 



