Physa is a genus of small, left-handed or sinistral, air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the subfamily Physinae of the family Physidae.
Physa
Physidae, commonly called the bladder snails, is a family of small air-breathing freshwater snails, aquatic pulmonate gastropod molluscs in the superfamily Lymnaeoidea.
Physidae
Physella heterostropha halei of the Central and Southern USA, about 1 cm long.
The sinistral shell of Physella acuta