Key to Families of Freshwater Snail
1a. Shell coiled…………………………………………………………………………...2
1b. Shell not coiled but flat, limpet shaped……………………………………………Ancylidae
2a. Shell planospiral (coiled in a horizontal plane)…………………………………..Planorbidae
2b. Shell conical (cone shaped, coiled in a vertical plate)…………………………..3
3a. Aperture on the left side of shell (sinistral)………………………………………...Physidae
3b. Aperture on the right side of shell (dextral)………………………………………..4
4a. Shell with operculum…………………………………………………………………5
4b. Shell without operculum……………………………………………………………..Lymnaidae
5a. Operculum concentric (or concentric with a spiral nucleus)…………………….Viviparidae
5b. Operculum not concentric…………………………………………………………...6
6a. Operculum multispiral………………………………………………………………..Valvatidae
6b. Operculum paucispiral……………………………………………………………….7
7a. Amphibious (found at periphery of water)………………………………………....Pomatiopsidae
7b. Fully Aquatic (always found in water)………………………………………………8
8a. Adults small (<10mm), shell often subhyline, males possessing a verge,
shell always smooth…………………………………………………………………..Hydrobiidae
8b. Adults large (>10mm*), shell never subhyline, males lacking a verge,
shell either smooth or sculptured……………………………………………………Pleuroceridae
*Adult shells of Leptoxis arkansensis (Pleuroceridae) and spring dwarfed Elimia potosiensis (Pleuroceridae) may be smaller than 10mm but can be distinguished from members of Hydrobiidae from its relatively thicker shell (not easily crushed with fingers) and males lacking a verge.
Constructed by David M. Hayes
Environmental Sciences Doctoral Student
Contact Info - david.hayes@smail.astate.edu
Web designed by Kentaro Inoue
Contact Info - kentaro.inoue@smail.astate.edu
