166 Records of the Indian Museum. [Vol. XIV, 



seems, in this district at any rate, to be associated with life in an open 

 lake. 



In order to avoid confusion I have confined the foregoing statement 

 about Taia to species from the Shan Plateau, with a passing reference 

 to those found in other parts of Burma. Before proceeding, however, 

 to consider variation in the bivalve shells of the lake and its vicinity it 

 will be convenient to discuss briefly certain cases from other countries 

 parallel at any rate to some extent to that of the Shan Taiae. The most 

 important cases are those of Margarya in Yunnan and of a remarkable 

 series of Vivipara described from Tertiary deposits in Austria. 



Margarya is a genus of Viviparidae known only from Western China. 

 All the forms as yet discovered have been assigned by conchologists 

 to a single species, M. melanioides, Nevill ; but eight or nine varieties 

 have been described. Some of these are apparently constant and at 

 least as distinct from the typical form as T. theobaldi or T. shattensis is 

 from T. ohesa. The shells resemble those of the species of Taia in sculp- 

 ture, but are much thicker and larger and have not the expanded 

 columeller callus characteristic of my genus. I have examined a large 

 series of fresh and subfossil specimens from Tali-Fu in Yunnan, the 

 type-locality. They include representatives of three of the varieties 

 {carinata, Neumayr, rofundata, Neumayr, and francheti, Mabille) as well 

 as of the typical form, of which we have the type-specimens. Indivi- 

 duals intermediate between the typical form and carinata are common, 

 but I can find none between the latter and . rotundafa or between 

 rotundata and frayicheti, which I am inclined to regard as distinct 

 species. I have not seen the forms called var. Monodi, var. Mansuyi, 

 and var. ohsoleta by Dautzenberg and Fischer, ^ but they also seem 

 likely to be specifically distinct. Among the eight or nine forms there 

 are two groups, in one of which the spire is moderately elongate and 

 more or less conical, while in the other it is greatly produced and almost 

 cylindrical. In both groups we find a transition from almost smooth 

 shells to shells ornamented much as in T. elitoralis. We find none, 

 however, that have the sculpture so regular as in T. intha, and none 

 in which the shell is so globose as in T. ohesa or even T. naticoides . 



Unfortunately we know very little about the types of environment 

 in which these forms live or lived. Dautzenberg and Fischer^ say : — 



"La forme typique du Margitrya melanioides et les varietes Delavayi et Monodi 

 sont representees dans les recoltes de M. Mansuy par des exemplaires provenant du 

 gisement quatemaire du deversoir du lac de \'unnan-Sen, a Koui-An. 



La var. Mansuy est pEus aLondante que les autres formes : M. Mansuy en a recolte 

 des specimens actiiels (fig. 2) dans les lacs de la Chaiissee, a Mong-Tse ; il I'a trouvee 

 egalement dans les gisements quateniaires de Tong-Hai (fig. 3), jusqu'a 50 meters 

 d'altitude au-dessus du niveau du lac actuel, et dans le quatemaire de Mong-Tse, pres le 

 ville (fig. 4) 



La var. ohsoleta n'a ete recueillie que dans les gisements quateniaires des lacs de la 

 C'haussee, plaine de Mong-Tse (fig. 5) et de Tong-Hai. 



Les var. Francheti, Mab. et tropidophora, Mab. n'ont pas ete rapportees par M. 

 Mansuy." 



Thus some of the forms are apparently extinct. Mr. J. Coggin Brown 

 of the Geological Survey of India, who collected a large series of shells 



1 Journ. Conch. (Paris) LIU, pp. 420-425, figs. J -5, 



