It does not look like Nerita polita it was alive when you collected, it seems other species of Nerita. If the shell is very old it might have faded in sunlight at dry place as dead. Then I can say Nerita polita. 

clarify your question !!   if you are asking about shell's coiling nature,  then  it's dextral (right handed rotation)...  

I'm not specialist on this area...anyway it seems fresh, I mean well-preseved. Could it be an albino specimen. What about scale bars...Is it juvenile?

Dear Ravikumar and Das, 

    Question is Nerita polita is different forms; Like Nerita polita f antiquata Récluz, 1841, Nerita polita f polita Linnaeus, 1758, Nerita polita f rumphii Récluz, 1841 like that. Revision of http://zoolstud.sinica.edu.tw/Journals/47.4/481.pdf  revision Nerita polita f rumphii Récluz, 1841 referred to as Nerita litterata Gmelin, 1791, 

http://zoolstud.sinica.edu.tw/Journals/47.4/481.pdf

I think Vittorio Garilli  Answer may be correct  albino specimen of Nerita litterata Gmelin, 1791 or ?. But more than 30 specimens i got...

Dear Dr Yambem Tenjing, Live Specimen collected, and see the photograph matured shell, spire, and columella specimen is not too old.

No creo que sea Nerita polita Linnaeus, 1758, esta tiene un perfil rectangular con la parte posterior redondeada, y una coloración definida, en la imagen se observa que, si fuera un juvenil no hay nungún vestigio de coloración,

Dear Dr Carlos Paredes, 

 No es un espécimen juvenil completamente maduras, algunas familias es mayor variación en juveniles y adultos, por ejemplo: Strombidae es mayor variación en juvenil a adulto, pero no Nerita así.

puede ser la forma albina de Nerita litterata

Gracias algunos mucho

Saludos

Ravinesh

For me it's just an albinic specimen of N. polita. N. litterata don't live in your area, like N. antiquata (maybe only Queensland and Northern Territory). N. maxima have a different "denticulation" on the columella.

Gianluigi

Dear Dr Gianluigi Bini, 

  Your opinion is correct. What about the possibilities albino form of Nerita lirellata Rehder, 1980?. 

Ravinesh

No I don't think this hypothesis. Teething columellar of N. lirellata (as all Lisanerita) is very weak. Besides the numerous lines of growth that can be seen on the spire of your sample, it looks just typical of N. polita.

I enclose a good image of N. lirellata.

Hello Gianluigi

Dear Ravinesh

The illustrated specimen looks like genuine Nerita polita Linnaeus, 1758. To me it does not give impression of being an albino as the initial whorl retains pinkish color.

Best

Syed

As I see albino shells may do that in early whorls

Dear Vittorio

Once the pigmentation has started in initial whorls, why should genetic program abruptly stop to initiate non-pigmented shell growth? How in a biological system this qualifies to be called as albino shell? Partial Albinism is not permitted in biology! You may like to have a look at the "Algorithmic Beauty of Sea Shells" by Hans Meinhardt, Springer 1995.

Best

Syed 

Dear Syed,

Sorry, I can't read the paper you suggested as I have no permission. Furthermore I'm not specialist on this matter, not biologist and can't answer to your logic question addressing biological/genetical reasons.

Anyway. I know that cases of semi and partial albinism in mollusks (though rare) do exist. Please see the attached paper at pages 17-19. Particularly, in the right valve of the specimen in fig. 1b the early shell looks like whitish, the rest is reddish. And what about the right valve in fig. 1c?

Also note that in bivalve mollusks growth goes symmetrically relative to left and right valves

Thanks for your attention

SALUTI

Vittorio

Dear Vittario

I am also not a specialist in Albinism in Mollusks! I wish you could cite actual specimens of Gastropods to make your point. Anyway thanks for providing reference of Lars Kellner. The illustrated bivalves on p.18 claimed to be showing complete, Semi- and partial albinism are rather strange as the pigmentation bands run perpendicular to the growth lines. The case of Nerita polita is somewhat difficult to explain.

Best

Syed 

Dear Syed,

I really appreciate your attention.

The paper I uploaded was just to show that partial albinism may exist in mollusks (as well in other far distant groups does).

As for the gastropods I found this image of Perotrochus as at http://www.schnr-specimen-shells.com/25642.JPG showing similar case as in Nerita. Please compare it to other conspecific colored shells from the same site (http://www.schnr-specimen-shells.com/Pleurotomariidae.html). Note that in the image I selected the specimen assumed to be albino has the very early whorls colored.

Also see http://www.shells-of-aquarius.com/murex-shells.html

Frankly I don't know if these cases are actual (genetically verified) albinisms, but one could be doubtful about the sharp connection albinism/totally white. AndI don't want to make any sharp point, just like to learn or try to satisfy my curiosity.

SALUTI

Vittorio

thank you Syed  and Garilli