Mollusca of the Tai-Hu. 305 
The body-whorl is relatively larger and the spire tapers less evenly in shells from 
the Tai-Hu than in topotypes of Benson's species from Cantor's collection. In this 
respect my specimens agree with topotypes of M. ningpoensis, Lea. It is clear, 
however, from the collection in the Indian Museum that the species is a plastic one. 
The measurements in millimetres of three normal shells from the neighbourhood of 
the Tai-Hu are as follows. In all the tip is eroded : — 
Length. Breadth. Aperture. 
22-5 8-5 7-25 X 3-5 
20-5 6-25 575 X 3-3 
1675 6-25 5 X 3-5 
The first two specimens are from the lake, the last from a canal at Soochow. In 
the latter locality the shells are smaller and less eroded and have the body-whorl more 
inflated than those from the Tai-Hu. 
Heude [op. cit., pi. xliii) has published Rathouis's figures of the radula and of 
various points in the anatomy. 
The species is common in all parts of the lake, both among stones at the margin 
and on a muddy bottom in 3 metres. According to Heude it and his M. erythrozona, 
which is perhaps no more than a phase of the widely distributed M. tuherculata 
(Miiller), are the only two real lacustrine Melaniae found in China. M. cancellata 
occurs in the watersheds of the Yangtse, the Hoangho and the Amur. 
Family HYDROBIIDAE. 
This family is represented in the Tai-Hu fauna by five species, two of which 
{Bithynia striatula and B. longicornis) are common and widely distributed in China. 
The other three, two of which are minute forms, have not hitherto been described. 
One of these belongs to the interesting genus Hypsohia, Heude, another to Stenothyra, 
Benson, and the third to a genus hitherto undescribed. The last is remarkable not 
only for its large size, but also for the extraordinary resemblance of the shell to that 
of Vivipara. 
Genus Bithynia, Gray. 
Bithynia striatula, Benson. 
1842. Paludina (Bithynia) striatula, Benson, Ann. Mag. Nat. Hist., IX, p. 488. 
1855. Paludina {Bithynia) striatula, id., Journ. As. Soc. Bengal, XXIV, p. 131. 
1882. Bithynia chinensis and spiralis, Heude, op. cit., pp. 171, 172, pi. xlii, figs. 8, 8a, 9, ga. 
1901. Bithynia striatula, Pilsbry, Proc. Ac. Nat. Sci. Philadelphia, LIU, p. 405. 
Pilsbry {op. cit.) has discussed the synonymy of this species. I have examined 
specimens from the following locahties : — Canton, Swatow, Chusan, Soochow, the Tai-Hu 
and Peking in China, Mukden in Manchuria and Lake Biwa in Japan. The specimens 
from Chusan are from Cantor's collection and were named by Benson. They may be 
regarded, therefore, as co- types of the species. Except those from Japan, which be- 
long to Pilsbry' s race japonica, the shells in this large series are fairly uniform, differing 
mainly in colour (from pale olivaceous to dark reddish) and size. They vary also in 
the prominence of the spiral ridges, not altogether in correlation with environment. 
