1918.] N. Annandale : Molluscs of the Inle Lake. 105 



is no reason to think that this species differs from its congeners in habits. 

 It lives at the edge of water and can doubtless swim attached shell- 

 downwards to the surface film, but does not lead a true aquatic life. 

 My reason for referring to it here is the remarkable resemblance 

 between its shell and that of a Limnaea to be discussed later (p. 109). 



Succinea indica, Pfeiffer. 

 Plate X, figs. 10, 11 ; plate xi, figs. 5, 6. 



1876. Succinea indica, Hanley and Theobald, Conch, hid., pi. Ixvii, figs. 1 & 4. 

 1914. Succinea indica. Glide, Faun. Brit. Ind., Moll. 11, p. 447. 



Living specimens were found at the edge of the Inle Lake at Thale-u 

 on the eastern shore and in the swamp at the northern end. Subfossil 

 shells occur in considerable numbers in the superficial deposits on the 

 He-Ho river just above its gorge. 



Shells from the Inle Lake (fig. 10, pi. x) agree as regards outline 

 and general appearance w4th Theobald and Hanley's figures, but are 

 rather smaller (14 mm. long) and of a darker colour. The animal is 

 that of a normal Succmea. I figure the jaw and a central and a lateral 

 tooth from the radula (pi. xi, figs. 5, 6). Subfossil shells from the He-Ho 

 river (pi. x, fig. 11) are thicker and have the growth-lines so coarse 

 that the surface approaches that of S. plicata, Blanford, in sculpture. 

 They do not differ otherwise from living shells. 



The species is essentially a Himalayan one, hitherto known from 

 Kumaon and Kashmir. Gude {op. cit., 1914) doubts the identity of 

 Egyptian shells assigned to it by Jickeli. 



Family LIMNAEIDAE. 



Genus Limnaea,^ Lamarck. 



The genus is cosmopolitan and capable of living in conditions 

 generally unfavourable to molluscs, for example at great altitudes and in 

 great depths. Its shell is remarkably plastic and varies in size, shape, 

 thickness and colour with changes in the environment. This character 

 of plasticity is admirably illustrated by the forms found living and 

 fossil in the Inle and He-Ho basins. I have been able to recognize 

 only three species among the living forms, but one of these has several 

 fossil and subfossil phases. I have also to refer briefly to a fourth 

 (fossil) species represented in our collection by two imperfect shells. 



The three living species fall into two well marked groups and in 

 one of these a remarkable series of shells can be arranged, linking 

 together two living species unlike' in shell-characters by means of 

 several apparently extinct phases. The third living species has two 

 distinct phases, each of which lives in a different kind of habitat. 



^ I take this opportunity to state that the species from Japan described by Preston 

 (Ann. Mag. Nat. Hist., (8) XVII, p. 160, pi. ix, fig. 6, 1016) under the name Litho- 

 tis japnnica is not related to the Indian species of Lithotis and does not belong to the 

 Succineidae. The radula is that of a Limnaea. The shell is like that of L. brevispira, 

 von Martens. 



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