i believe they are the same ones i have. and that wouldn't be pond
snails. they are sinistral ie. left-coiled snails. aka. physa
FWIW...the snails American aquarists call "pond snails" *are* Physa species.
There are a lot of different species, from tiny to about 1" long. The general
shape of all of them is sort of football-shaped. I never noticed which way the
shells coiled. I'll have to check it out, when the tank lights go on.
Leigh
http://www.fortunecity.com/lavender/halloween/881/