Snails in the family Physidae have shells that are sinistral, which means that if the shell is held with the spire pointing up, and the aperture is facing the observer, the aperture is on the left-hand side.
The shells of Physella species have a long and large aperture, a pointed spire, and no operculum. The shells are thin and corneous and rather transparent.
Drawing of the eggs of Physella gyrina: upper image is the egg-mass showing position of eggs in envelope. Lower images is a single egg showing the position of an embryo.
