SOME MEDUSA OP JAPANESE WATERS. 17 



part of oral arms, whence again they become gradually short and 

 narrow as they approach the axis of the body. The thin hang- 

 ing parts on both sides of the mid-rib of oral arms are much ruffled 

 and very broad, broader than the length of the oral arm ; those 

 of one and the same arm are developed exactly alike, touch each 

 other, and are often united here and there along the margins. 



The muscular system is well developed. Outside the stomach 

 cavity, there are fine, parallel, concentric ridges about fifteen in 

 number ; besides, there exist about five concentric ridges in the 

 proximal parts of the oral tube. In the tentacular region, there 

 are sixteen bundles of radial ridges, which number about fourteen 

 in each bundle. The minute canals in the concentric ridges are 

 nearly uniformly developed ; each of them sends forth from five 

 to eight, short and crowded branches. 



The tentacles are long and numerous. They are grouped in 

 eight U-shaped tracts. About three or four rows of tentacles are 

 found at the proximal base of the tract. 



The reproductive elements are developed in the four inter- 

 radial sexual glands as well as on the inner side of oral arms in 

 small patches of irregular shape but chiefly near the margin along 

 which the curtain-like parts of both sides are united. 



The umbrella is deep orange in color, the oral arms light 

 orange-brown, the male genital gland light orange-yellow, the 

 female genital gland dark yellow-brown, and the tentacles reddish 

 in distal parts. 



The umbrella measures about 300 mm. in diameter. 



I have found this species rather abundant on the eastern 

 coast of Poromushiri in October 1904. An incomplete specimen, 

 belonging most probably to this species, was collected by Prof. 

 Ijima's party near Korsakoff", in September 1906. 



