630 



Records of the Indian Museum. 



[Vol. XXII, 



this species have been found — a broad form in ponds and a narrow 

 form in a small stream. In the Manipur Valley and at Dimapur 

 no less than four such phases occur. Two of these are almost 

 identical with the two from the vShan States and inhabit similar 

 types of environment. A third phase, still narrower than that 

 found in rapid running water in the valley, inhabits higher parts 

 of the same streams, where they have the character of mountain 

 torrents. Perhaps, however, the most interesting phase is that 

 found at Dimapur in small cattle-ponds. It may be described as 

 both intermediate in some mdividuals between the pond phase 

 and the ordinary stream phase, and also, in other individuals, as 

 a more extreme form of the pond phase. A partial explanation 

 is probably to be found in the fact that the ponds it frequents are 

 connected in the rainy season with small streams. The narrower 

 individuals may be those that have grown up in these temporary 

 streams, while the broader individuals are those that have never 

 left the ponds 



We thus see that whereas the type of plasticity characteristic 

 of L. andersoniana is essentiallj' similar in the Inle and Manipur 

 Valleys, that observed in the Viviparidae is different in kind in the 

 two localities. We do not find any species of mollusc in Manipur 

 that exhibits the extreme variability in | shell-sculpture of Taia 

 naticoides, in the Shan States, and even in L. acuminata variability 

 in shell-form is much less marked in the Loktak Lake than it is in 

 many other localities. In the present state of our knowledge it 

 is as well not to speculate further as to the meaning of these 

 observations. 



ADDENDUM. 



Note on Sphaerium montanum^ Tapparone-Canefri. 



Since this paper went to press I have, through the kind 

 offices of Dr. R. Gestro of the Genova Museum, had an opportu- 



1 EXT-FiG. 36. — Type-shell of Sphaerhtm Text-fig. 37.— Hinge ot the same. 

 montauum, Tapparone-Canefri. 



nity of examining the unique type-specimen of Tapparone-Cane- 

 fri's Sphaerium montanum from Tenasserim, Burma, which I had 



