Does anybody remember the "Mini-mystery snail"?

No, those aren't it, they're just assorted Nerites.

Though I'm not sure what species the Mini-mysteries are, they're definitely not Nerites. I can't find many pictures of them on the net, but these two should give a good idea of what they look like.

minimysteryteksti.jpg

05-06-25-littlesnail2.jpg
 
The picture in the first thread seems like the same snail as well. Unfortunately, not much information there.

The other two don't really seem to relate.
 
hmmmm - quite a mystery - I guess that's why they're called mini mystery snails :) sorry, couldn't resist.
 
hmmmm - quite a mystery - I guess that's why they're called mini mystery snails :) sorry, couldn't resist.

It'd certainly be appropriate!

It is starting to resemble Bithynia tentaculata to me, though they aren't the same size. I wonder if it could be another Bithynia species, or even a morph of Bithynia tentaculata that doesn't grow as large.
 
Those look like viviparus species to me. They don't have quite the classic dark viv color of V. malleatus or V. viviparus, but some of the smaller viv species have that mottling and the lighter brown color. That unmistakable shape of the snout is spot on though, and the shell shape as well. I'm 90% sure they're one of the smaller viv species like V. mammilatus or V. contectus.
 
I've thought it could be a Viv as well, but I couldn't find any that small. Both mammilatus and contectus are much larger than the 5mm Mini-mystery.
 
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