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446 ZOOLOGY OF THE FAR EAST. 
6. Station 14, off Suga^ on west side of lake, 52 metres, fine grey mud, 2-X-15, 
eight specimens. 
7. Station 15, West Coast of Oura Bay, at north end of lake, 17-31 metres, sand 
mixed with mud, 2-X-15, ten specimens. 
8. Station 22, Hikone Fishery Station near the east side of the lake, in irriga- 
tion channels among weeds, about fifty specimens. 
9. Off Komatsu, 30 feet, fine gravel, seven specimens. 
10. Off Komatsu, in the interior of Spongilla dementis, five young specitnens. 
11. Zeze, on lower surface of stones on shore, 3-X-15, about forty specimens. 
Northern Japan. 
12. Sapporo, Hokkaido (Yezo), April 1915, e. coll. Akatsuka, about forty speci- 
mens. (Presented by Dr. T. Kawamura.) 
Description. — First three somites of the pleon with a fringe of 10-12 short fine 
hairs on the median dorsal portion of the posterior margin, their lower margins with 
three or four spiniform setae and a few hairs on the anterior portion, postero-lateral 
corner acute and slightly produced. PI. XX, fig. 14 shows the lower margin of the 
third pleon somite in one of the specimens and gives the essential structure of these 
somites in this species. The fourth to the sixth pleon somites (pi. XX, fig. 18) are 
armed with spines on the dorsal surface. On the fourth and fifth somites there are 
two pairs of dorsal spines and a few short setae, on the sixth pleon somite there is 
only one pair of spines, one on each side. There is considerable variation in the 
number of sphies on these somites and the figure I give showing their arrange- 
ment must be taken as the average typical armature. 
Head not rostrate, antero-lateral angles rounded. 
Eyes moderate in size, broadly oval, almost circular in outline, pigment black. 
Side-plate 4 (pi. XX, fig. 11) with the posterior angle distinct but obtuse and the 
margin above slightly concave. 
First antenna (pi. XX, fig. i) not half the length of the bod}^, second joint of the 
peduncle as long as the first but narrower, third joint of the peduncle rather more 
than half as long as the second, primary flagellum with about 20 joints, accessory 
flagellum with 5 joints, the terminal joint miinute. The whole appendage is but 
sparingly provided with setae. 
Second antenna (pi. XX, fig. 2) about |- | of the length of the first, the peduncle 
reaching beyond the level of the peduncle of the first antenna. There is variation in 
this character. In som^e specimens the peduncle of the second antenna outreaches 
that of the first by half the last peduncular joint and in other specimens the differ- 
ence is much less. The last joint of the peduncle is shorter than the fourth and the 
flagellum is composed of about 12 joints. The males have a few calceoli on the flagel- 
lum joints. Month parts are normal for the genus Gammarus. The first maxilla has 
the inner lobe moderately broad with about 18 plumose setae on the inner margin 
and 6 or 7 simple setae on the distal part of the outer margin. 
The second thoracic limbs (first gnathopods) of the female (pi. XX, fig. 6) with the 
propodus rather larger than the carpus, somewhat dilated, palmar margin oblique 
