MoUusca of Ivake Biwa. 45 
all the shells appeared to be dwarfed, but the external sculpture is not correlated in 
any way with environment. The species is extremely variable in this respect. 
The typical form has been found only in Lake Biwa, but specimens of " var. 
minor, Smith," the identity of which is very doubtful, have, according to Brot, been 
recorded from Formosa by Mollendorff. 
Mclania niponica, Smith. 
(PI. Ill, fig. 3, A, B.) 
1874. Melania niponica, Brot, op. ciL, p. 338 (in part), pi. xxxiv, fig. 10. 
1902. Melania niponica, Pilsbry, op. cii., p. 119. 
1902. ? Melania japonica, id., op. ciL, p. 120 (? lapsii). 
Although this species closely resembles M. biwae, Kobelt, it is easily distin- 
guished by the structure and form of the mouth of the shell (see pi. Ill, figs. 3, A, B) 
M. niponica is only found on rocks or stones, on which it is very abundant. 
The typical form occurs with M. lihertina on small stones at the south end of the 
lake, but at Chikubushima and other places where rocks descend vertically into the 
water to considerable depths, a much larger and more deeply sculptured phase occurs 
in great abundance. Specimens from small stones on the landing stage at Chikubu- 
shima provide, however, an almost complete transition between the two phases. 
The species is only known from Lake Biwa. 
Melania biwae, Kobelt. 
(PI. Ill, fig. 4.) 
1879. Melania biwae, Kobelt, op. cit., p. 416, pi. xix. fig. 9. 
1902. Melania biwae, Pilsbry, op. cit., pp. 119, 120. 
This species is found on the rocks at Chikubushima with M . niponica . It is 
apparently scarce, but its resemblance to M. niponica has probably led to much 
confusion. 
It is only known from Lake Biwa. 
Family HYDROBIIDAE. 
Geuns Bithynia, Gray. 
Bithynia striatula var. japonica, Pilsbry. 
1901. Bithynia striatula var japonica, Pilsbry, Proc. Acad. Nat. Sci. Phil. LIU, p. 405. 
1902. Bithynia striatula var. japonica, id., ibid., LIV, p. 121, pi. ix, figs. 9-12. 
Two specimens taken on a stone at the edge of the lake near Zeze agree exactly 
with Pilsbry's figure 9 of a specimen from Hidachi. The form is probably not really 
lacustrine : my examples were taken in a backwater almost separated from the lake. 
The subspecies is only known from a few localities in the Main Island of Japan, 
in which it is widely distributed ; Lake Biwa being near the middle of the known 
range. The typical form is found in China and Cambodia. Heude ^ says it is com- 
mon in all the lake systems of the Blue River. 
1 M6m. Nat. Hist. L'Emp. Chinois, I, Moll, d'eau douce, p. 171, pi. xlii, figs. 11, iia (? 1882). 
