A Snail's Tale: Triodopsis - Part 1

Of the multiple species of land snails that live in our yard, I'm going to discuss Triodopsis sp. first. Members of the family Polygyridae, these snails have about 4-6 whorls on their shells, which are striated all over, including the underside, not smooth and polished like other snails' shells. Their bodies are a dark blue, grayish color; like other snails, they have eye tentacles, a pneumostome, and a foot. Basically, a snail is a slug with a shell.

At first I believed these snails belonged to the genus Ventridens, a common genus in South Carolina, but now I'm thinking Triodopsis is a better fit. Called "three-toothed snails," the genus is characterized by 3 "teeth" around the lip of shell, helping to prevent predators from getting at the snail inside. This doesn't always work, however. I often find empty shells around the yard.

If you think these snails belong to another genus, please let me know. Also, if you can identify the species, I'd appreciate the info.

You can see this snail has faint stripes around its shell.

You see that this snail's shell has a reddish/brownish tint:

References:

http://www.scwildlife.com/pubs/julyaug2006/gardensnail.html

http://entnemdept.ufl.edu/creatures/misc/gastro/terrestrial_snails.htm (general biology)

http://eol.org/pages/50329/overview (taxonomy)

http://www.jaxshells.org/triodopsis.htm (good photos of the shells of diff. species of Triodopsis)