Z00L0(>1ICAL KKSLILTS OF A TOUR IN THE FAli EAST. 
THE VIVIPAROUS WATER-SNAIL OF LAKE BIWA, JAPAN. 
By N. Annandale, D.Sc, F.A.S.B. [Zoological 
Survey of India, Calcutta). 
Ill revising the Indian Viviparidae I have hud occasion to re-examine the large 
collection from Japan and China preserved in the Indian Mnsenm, including the 
specimens collected by myself in 191 5. The result has been, so far as the Japanese 
forms are concerned, to throw light on an interesting species from Lake Biwa which 
has hitherto been confused with Vivipava sclateri, Frauenfeld, but, as a study of the 
development of the shell demonstrates, is distinct from that species generically. 
Vivipara sclateri was described in 1865 by Frauenfeld,' who gave a good figure, 
but no locality more precise than "Japan. " Kobelt ^ in his monograph of the land 
and freshwater molluscs of Japan originated the confusion about the Biwa species, 
whix:h he figured under the name Paludina ingallsiana. All his figures under this 
name, however, do not represent it, but only fig. 17 on his plate X (young) and fig. 2 
on plate XI (adult). The confusion was perpetuated by IwakawaMn his account 
of the Japanese Viviparidae and Pilsbry* did not put the matter straight in his 
observations on the same subject. Kobelt ^ in his later work in the Conch. Cab. left 
it where it was, and finally in my own account of the molluscs of Lake Biwa 
I accepted the identifications supplied to me by conchologists, being then interested 
in the molluscs from a biological rather than a systematic point of view. 
The key to the whole confusion is to be found in figs. 13 and 17 of pi. X in 
Kobelt's paper (1879), which illustrate clearly the differences between the young shell 
of V. sclateri and that of the Biwa species. 
With this introduction I may now describe the latter. 
Fain. VIVIPARIDAE. 
Genus Heterogen, nov. 
Adult shell fairly thick, of large size, high and narrow, subbiconical, imperforate 
or rimately perforate, with the aperture rather small and the collumellar callus not 
I Fraucuiuld, Verh. Zcol. bat. (ies. W len XV, p. 531, pi. 22 (1865). 
i Kobelt, Ahh. Sencken. Nat. Ges. XI (1879). 
3 Iwakawa, A-nnol. Zool. Japon. I, p. 85 (1897). 
+ Pilsbry, Proc. Ac. Nat. Sci. Philadelphia LIV, p. ri8 (1902). 
& Kobelt, Paludina in Chemnitz's Conch. Cab. (1909). 
« Anuandale, Mem. As. Soc. Hrn«al VI, ]). 46 (1916). 
