Eye Placement
Unlike most land snails that have two eyes at the tip of their antennae, the Fossaria parva’s eyes reside at the base, which is the defining characteristic of the species order.  This could be due to the fact that  the pygmy fossaria does not stick their head out of their shells when moving on land which is, again, not like most other land snails; the placement of the eyes allow the animal to still see where it is going. (The Skipper Project, 2011)

Loss of Operculum
Those snails in the genus Fossaria do not have an operculum, which is a small plate that is used to cover the entrance into the shell when the animal retreats inside and prevents water loss.  This structure may have proved to be unnecessary because of two reasons.  One, most members of this genus are freshwater animals, therefore water loss is typically not a problem and two, those like the Fossaria parva do not fully emerge from their shells while moving; it is as if they are constantly in retreat. (Clifford, 1991)

As can be seen on my classification page, the pygmy fossaria is in the subclass Pulmonata, thus certain conclusions can be drawn when discussing how the snail has adapted to breathe in a freshwater environment.  All pulmonates share the same structure in reference to respiration: a small opening on their mantle called a pneumostome that draws air directly into their “vascularized mantle” that serves as a lung.  For the F. parva, and other aquatic pulmonates alike, water, instead of air, can be taken into the mantle cavity instead.  Upon enterance, the required oxygen is then removed from the water, turning the mantle into a type of “physical gill”. (Clifford, 1991)