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Ops, I forgot to put the size on this one. It is between 6-7mm. Thank you.
Is it too big for P.antipodarum at 6mm? Usually at 2-3mm
A lookalike is Lymnaea truncatula (at 7-12mm)
THREE MARINE PROJECTS
The average height of the shell is approximately 5 mm; maximum size is approximately 12 mm. The snail is usually 4–6 mm in length in the Great Lakes, but grows to 12 mm in its native range.
Being a prosobranch with an operculum the lip make a full circle as in the photograph. Lymnaea truncatula is not like this, the lip not being thickened against the body wall but only at the free edge of the last whorl.
Yes Martin, thanks.
I am about to post up a sighting from a new area near Inverness. They are nearly black, certainly very dark grey and none, in the thousands I found, were bigger than 2.5mm.
Following your link to this http://en.wikipedia.org/wiki/File:Potamopyrgus_antipodarum_shell.png suggests the rim (lip) of the opening to be complete all 'round.
But this http://en.wikipedia.org/wiki/File:Galba_truncatula.jpg (L.truculata) is incomplete.
Do you think that's a fair indicator for separation (from a photo)?
Yes, that is the point I was trying to make.
Thanks again Martin
Lat/Lng: 51.6938, -1.3291
OS grid ref: SU464996