142 Recorth of tJie Indian Museum. [Vol. XIY, 



No species of Corbicula was found in the Inle Lake, but C. noetlingi 

 is abundant in ponds, marshes and slow streams in its basin and also 

 in similar situations at He-Ho and Thamakan. Even the thinnest- 

 shelled forms of the genus would sink in the semi-liquid mud of the 

 lake. 



The species was described from the Northern Shan States. 



Pisidium casertanum (Poli). 

 Plate xix, figs. 13, 14. 



? 1878. Pisidium hydaspicola, Theobald, Journ. As. Soc. Bengal, XLVII, p. 147. 

 1900. Pisidium (Fluminina) dubium, Lindholm in Korotneff's Wiss. Ergehn. 



Zool. Exp. Baikal-See, IV (Moll.), p. 8.5, pi. ii, figs. 45, 4G. 

 1913. Pisidium casertanum. Woodward, Cat. Brit. Pis., p. 31, pis. i, figs. 3-6, 

 iii, fig. 3, xiii-xviii. 

 ? 1915. Pisidium hydaspicola, Preston, op. cit., p. 225, fig. 27. 

 1916. Pisidium casertanum, Annandale, Mem. As. Soc. Bengal, VI, pi. i, p. 53, 

 pi. iii, fig. 14. 



Specimens from the Inle Lake and the He-Ho plain are so like those 

 from Japan, examined by Woodward, in structure and appearance that 

 they must be assigned to the same species. Their shells differ from 

 those from Lake Biwa in being as a rule still smaller, in being subtrun- 

 cate posteriorly and in having the umbo more prominent. In outline 

 they closely resemble Lindholm's figure of his P. duhiu?n from Lake 

 Baikal, but the shell is smaller, evidently thinner and more transparent 

 and the external striae closer, finer and more regular. A specimen 

 from the He-Ho stream is more globose than those from the Inle Lake 

 and a little broader. 



The following measurements (in millimetres) are those (A) of the 

 He-Ho shell, (B) and (C) of shells from the lake. 



Length 



Height 



Transverse diameter 



Height to length 



Transverse diameter to height 



Transverse diameter to length 



The specimen from the He-Ho was found in a crevice in the bark 

 of a tree-trunk submerged at the edge of the stream in a kind of small 

 backwater. In the soft mud of the central region of the Inle Lake 

 the species is not uncommon. In shells from this mud the posterior 

 extremity is coated with a reddish substance precisely as in Japanese 

 deep-water specimens. There is no deposit of the kind on the He-Ho 

 shell. 



P. casertanum is widely distributed in Europe. In Asia it 

 has been reported only from Lake Baikal in Siberia (2-3 fathoms) and 

 from deep water (17-30 fathoms) in Lake Biwa in Japan. It seems to 

 me by no means improbable that P. atkinsonianum, Theob., which is 

 not uncommon in small pools in streamlets in the Eastern Himalayas 

 at altitudes between 5,000 and 10,000 feet, is merely a dwarfed 

 form of the species, and I am very doubtful whether P. hydaspicola, 

 Theob., from Kashmir is specifically distinct. 



