Mollusca of the Tai-Hu. 
315 
Vivipara cataycnsis (Heude). 
1882. Paludina catayensis, Heude, op. cit., p. 174, pi. xxxix, fig. 10. 
igog. Vivipara {chifiensis ? subsp.) cathayensis, Kobelt, op. cit., p. 112, pi. xviii, figs. 5. 6. 
My specimens from the Tai-Hu vary in shape and sculpture and seem to provide 
a complete transition, so far as these are concerned, between V . catayensis as figured 
by Heude and by Kobelt and V . itssuriensis as figured by the latter author {op. cit., 
pi. xviii, fig. 1-4). In shells from Mukden, however, which Dr. T. Kawamura has re- 
cently sent me and which I believe to represent the true V. ussuriensis, the mouth 
is narrower and longer and the shell thinner and less opaque ; the black margin of the 
lip is also narrower. It is probable, therefore, that the Tai-Hu form, which must 
bear the name catayensis, should be regarded as a local race of the northern species 
V. ussuriensis. 
This large and handsome Vivipara occurs in considerable abundance among 
weeds in creeks round the Tai-Hu. It is not found, however, in the open parts of the 
lake. 
LAMELLIBRANCHIATA. 
Family MYTII.IDAE. 
Two species of true mussels, Mytilus martensi, Neumayr ^ and Modiola lacustris, 
V. Martens, have been found in fresh water in the Yangtse system. Only one of these 
occurs in the Tai-Hu. 
Genus Modiola, Lamarck. 
In western countries this genus is exclusively marine and even in the Bay of 
Bengal a species {M. watsoni, Smith) occurs at depths of over 100 fathoms. At least 
two Indian species have, however, established themselves in estuarine tracts in 
brackish water and water of variable salinity, while in Siam and Cambodia allied 
forms are fluviatile and in China M. lacustris lives in the Tung-Ting Lake hundreds 
of miles inland. 
The precise relations of the Far Eastern freshwater forms are still obscure. I 
have examined co-types of M. lacustris from the Tung-Ting Lake and also what are 
probably co- types of M. cambodjensis, Morlet from Cambodia, as well as a series of 
shells from the Hang river in Corea, recently sent me by T. Kawamura. The differ- 
ences between them do not seem to me any greater, if so great, as those between the 
different phases of M. striatula^ recently discussed by Mr. S. W. Kemp and myself. 
Indeed, I think it not at all improbable that all are merely races of that species. I 
have not, however, material for a full discussion of the question. The form I name 
M. lacustris is, I am convinced, identical specifically with the one described under that 
name by von Martens, but it is not improbable that his species will finally rest in the 
synonomy of some other. 
Modiola lacustris, v. Martens. 
1875. Modiola lacustris, v. Martens, Malacoz. Bldtt. f. 1874 and 1875, p. 186. 
? 1870 1876. Modiola lacustris, Pfeiffer, Nov. Conch. IV, p. 154, pi. cxxxv, figs. 2, 3. 
1881. Modiola lacustris, v. Martens, Conch. Mitth. I, p. 97. 
1 Neuraayr, " Sussw.-Moll." in Wiss. Ergebn B6la SSzechenyi II, p. 640 (1887). 
2 Aunandale aud Kemp, Mem. Ind Mus. V, pp. 358-364, pi. xv (1916). 
