238 



Notes on some Indian and Burmese Helicidce. 



[No. 3, 



Notes on the variation of some Indian and Burmese Helicidw, with 

 an attempt at their re- arrangement, together with descriptions of 

 new Burmese Gasteropoda.— By W. Theobald, M$. } Junior. 



Since my paper on the distribution of our Indian terrestrial Mollus- 

 ca was read at the February meeting of the Asiatic Society, several 

 new species have accumulated on my hands, which I propose to de- 

 scribe in the present paper, and at the same time, to offer some remarks 

 on certain nearly allied forms, which a careful examination compels 

 me to consider, as merely well marked and persistent types of one 

 species, connected as they are by intermediate forms, whose number is 

 constantly on the increase. 



The question of where variation ends and specific separation is called 

 for, is of course not easily settled by any precise rule, and has always 

 been regarded as depending more or less on the peculiar views or 

 idiosyncracy of the individual naturalist, and has resulted in the 

 manufacture of an erroneous number of new species, ostensibly of 

 equal value, but many of them in reality entitled to no higher rank 

 than varieties. I myself have offended in this way ; but whilst depre- 

 cating for the future the creation of species, in the unqualified manner 

 hitherto too common, I prefer a specific (or sub-specific) name for all 

 well marked local forms, to the method advocated by some, of indicat- 

 ing such shells by a letter of the alphabet, as var A or var B of the 

 type, or first described individual, however little it may merit such 

 distinction save on the ground of mere priority. 



My friend Mr. H. F. Blanford, has already done good service by 

 decimating the ranks of shadowy species ranged under the genus 

 Tanalia, in his paper in Volume XXIII. of the LinnaBan Transactions, 

 wherein he reduces the twenty-six recorded species of the genus to two, 

 Tanalia violacea, Layard, and T. aculeata, G-mel. which last shell 

 exults in no less than twenty-four synonyms, (twelve contributed by 

 Keeve, nine by Dohm and three by Layard). 



This genus (Tanalia) well illustrates in my opinion the advantage 

 of retaining a distinctive name for well marked types of what, 

 critically viewed, is but one species, for a considerable amount of 

 obscurity, quite unredeemed by superior brevity, results from the use 

 of simple letters, rather than well chosen and distinctive epithets for 

 well marked local types, many of which have hitherto, though erro- 



