1918.] N. Annandale : ]\lolluscs of the Inle Lake. 165 



and Hsin-Dawng, because it has been possible to examine tbem in a 

 living condition. The three species are T. intha, T. elitoralis and T. 

 shanensis. The first two of these have a conical shell, while that of T. 

 shanensis is elongate-conoidal, but not so elongate as those of T. lacus- 

 tris and T. cylindrica. All the shells are thin or moderately thin and all 

 have a regular series of well-developed spiniform or subspiniform 

 squamous processes on the chief spiral ridge of the body-whorl. T. 

 intha and T. shanensis are constant species, while T. elitoralis is a 

 variable one. 



T. intha lives only in those parts of the lake in which the water is 

 clear and transparent. It has the most elaborately sculptured shell 

 of any of the species in the genus, and it varies as little as any. Shells 

 from the less congested parts of the outer edge of the marginal zone are 

 slightly larger on an average, a little broader than and not quite so 

 constant or so regular in sculpture and in shape as those of individuals 

 that live in the middle of the lake. Even the former, however, show no 

 real approximation to the shell of T. elitoralis. This species, which is 

 found living only in the intermediate zone of the lake amidst dense 

 aquatic vegetation, is much scarcer than T. intha. It is also very much 

 more variable both in shape and size, and has the sculpture decidedly 

 less regular. Some shells are much more elongate than others. On 

 the whole the species is nearest to the fossil T. conica from Hsin-Dawng, 

 but it is nearer to T. intha than it is to T. shanensis. 



T. shanensis does not reach so large a size as T. elitoralis, but is more 

 constant both in this respect and also in shell-form. It is indeed a fairly 

 constant species, although it lives in conditions very different from those 

 in which T. intha is found. It inhabits the comparatively foul water of 

 the marginal zone among floating islands, where circumstances are 

 favourable for the formation of peat. It is at least as closely related to 

 T. naticoides as to any other species. 



We have thus three species of Taia from each of the three lakes, 

 for there is every reason to suspect that the few shells of T. theohaldi 

 that have been found at He-Ho and Hsin-Dawng are adventitious so far 

 as their position is concerned. From the He-Ho lake we have T. inter- 

 media, T. lacustris and T. analoga ; from Hsin-Dawng T. ohesa, T. 

 cylindrica and T. conica ; from the Inle Lake T. elitoralis, T. intha and T. 

 shanensis. Each of the nine species is either conical, globosely conoidal 

 or elongate-conoidal in shell-form. To the first group belong T. analoga, 

 T. conica, T. elitoralis and T. intha ; to the second T. lacustris, T. cylin- 

 drica and, less definitely, T. shanensis, while in the third T. ohesa and 

 T. intermedia find a place. In the Inle Lake at any rate, the conical 

 type of shell is definitely associated with true lacustrine conditions, and 

 this was probably the case also in the other two lakes ; whereas the 

 globosely conoidal type is or was to be found rather in the swampy 

 marginal zone. The elongate-conoidal forms seem to have been strictly 

 lacustrine, but T. shanensis, which is intermediate between the globosely 

 conoidal and the elongate-rconoidal, is practically paludine in habits. 

 The non-lacustrine species {T. theohaldi and T. naticoides) may be 

 classified among the globosely conoidal forms. As all the conical 

 shells are also elongate, elongation of the shell in Taia, therefore, 



