Amphipoda with notes on a species of Isopoda. 
451 
tinguish that genus from Neoniphargus. The first maxillae are of the true Gammarus 
type and not of the intermediate form found in. Smith's two species. 
It would be interesting to be able to define more accurately the relationship of 
G. annanialei to the Australian and Tasmanian species in view of the occurrence of 
the genus Atyloides in Japan and Australia and the parallel case of Paratya among 
the Macrura. 
[This is the common aquatic x\mphipod of lyake Biwa. It is abundant on a mudd^'- 
bottom in from 50 to 77 metres and occurs more sparingly in shallower watef. It is 
also found, both in China aud Japan, in ditches and similar situations. The young 
apparently conceal themselves more carefully than the adults and their occurrence 
in the patent exhalent channels of a sponge [Spongilla dementis) is noteworthy. A^. A .] 
Gammarus pulex (Linn.). 
[PI. XX, figs. 19-27.] 
Locality. — Hills above Otsu, L. Biwa, among moss and gravel in small streamlet 
in wood, forty specimens, up to 11 mm. in length. 
Remarks. — I cannot find any characters of specific importance in which these 
specimens differ from typical Gammarus pulex. 
Chevreux (1907) has noted the most important points in which specimens of 
this species from different localities vary and it will be as well to describe the charac- 
ters of the Japanese specimens in these respects. 
1. The form of the lower posterior angle of the third pieon segment. — PI. XX fig. 25 
shows the form of this plate in my specimens. The lower posterior angle is slightly 
produced and bluntly pointed. There are three or four short setae on the posterior 
border and one stronger seta on the lower border. 
2. The spinulation of the last three segments of the pleon. — On the fourth and 
fifth somites of the pleon there is a pair of dorsal spines, with a pair of fine short 
setae between them and a pair of setae to the outside of each spine. There do 
not appear to be any lateral spines on these segments. On the sixth somite of the 
pleon there is a lateral spine (sometimes two), on each side of which there is a pair 
of setae. There is no dorsal pair of spines but the dorsal pair of setae is present. 
3. The accessory fiagelliim of the first antenna. — The specimens show considerable 
variation in the number of joints in this accessory appendage, from three joints 
of more or less equal size to five joints, four of which are subequal and the terminal 
joint very small, 
4. Armature of the telson. — PI. XX, fig. 27 depicts the telson of a male specimen^ 
II mm. Each lobe has two spines and four or five setae at the apex and a few setae on 
the lateral margins. 
5. The proportions of the rami of the third uropods (pi. XX, fig. 26). — The inter- 
nal ramus is about three-quarters of the length of the first joint of the outer ramus. 
I figure in addition the second and third thoracic limbs (first and second gnathopods) 
of both male (pi. XX, figs. 21-22) and female (pi. XX, figs. 19-20), the last tho- 
racic limb of the male (pi. XX, fig. 23) and the fourth coxal plate (pi. XX, fig. 24). I 
