1864.] 



Notes on some Indian and Burmese Helicidte. 



239 



neously, stood as distinct species. Whilst therefore concurring in the 

 results of Mr. Blanford's examination of the genus Tanalia, I would 

 prefer retaining the known designations of such well marked types as 

 T. Tennenfii, T. nerifoides, and the like, to recording them all as T. 

 aculeata, GemX var. A or var. B. 



The alphabetical or numerical method of discriminating varieties, 

 would certainly possess considerable advantages if all the varieties of 

 a species could be arranged in an unbroken right line, instead of one 

 very much given to ramification, but even in that case the type species 

 by priority would often have to be set aside, as falling naturally into 

 some other position, than at the head of the series ; I therefore shall 

 retain, in this paper, many names which I now regard as of merely 

 Sub-specific, value instead of discarding them in toto as soon as their 

 identity, if critically considered, with some previous species is establish- 

 ed ; and shall on the same principle, bestow distinctive names on those 

 which of the shells herein described I regard as merely local races. 



It might at first be imagined that strong support was derivable, 

 from the enormous variation of form of some widely spread species^ 

 for the Darwinian view of the gradual extension by migration of all 

 species in space, and the simultaneous change undergone by them, to 

 meet changed conditions of existence, resulting in local types, and 

 ultimately by the decay of intermediate forms, in so called distinct 

 species ; but this idea is speedily negatived by the consideration, that 

 though some species exhibit an amount of variation, which might be 

 plausibly accounted for by the Darwinian theory, yet others not less 

 widely spread, either as to time or place, exhibit little or no such ten- 

 dency, which seems rather a peculiarity (of temperament so to say,) 

 marking certain species, than the result of a general law regulating 

 the development of all. A notable example of this is afforded by the 

 little Helix labyrinihica, Say, which has remained unchanged during 

 the eons which have elapsed since the Eocene period, occurring fossil 

 in the Headon beds on the Isle of Wight, and living at the present day 

 in Alabama. Bulimus punciatus and JBulimus pullus i Gray, may also 

 be quoted, the first species inhabiting, unchanged to any perceptible 

 extent, the plains of India and the shores of Mozambique, whilst the 

 last ranges widely through India and some of the neighbouring coun- 

 tries, (Burma and even the shores of the Red Sea,) and occurs fossil in 

 the alluvial deposits in the Nerbudda valley , where individuals^ undis- 



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