A Snail's Tale: Ventridens - Part 1

In addition to Triodopsis, we also have snails in our yard belonging to the genus Ventridens. As I mentioned before, this is a common taxon in South Carolina. You'll notice that, unlike the Triodopsis specimens I showed you, these snails have shells that are glossier and more translucent, not as rough and opaque. Notice also that the colors alternate per whorl, and the shells are domed and softly striated. The body color, though, is very similar: a dark blue. I believe the snails could belong to Ventridens cerinoideus, or perhaps Ventridens demissus. Let me know if you think another genus or species would be a better fit. (I initially thought these were glass snails, belonging to Oxychilus, but their shells aren't flat enough; their domed shape suggests Ventridens.)

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Notice the open pneumostome on the snail's back, below the lip of the shell. By contrast, slugs have pneumostomes on their sides, on the lower portion of the mantle.

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References:
http://www.jaxshells.org/trxt.htm (cerinoideus)
http://www.jaxshells.org/f10a.htm (demissus)
http://eol.org/pages/50358/overview (taxonomy)