On my birthday hike with my older daughter, Emma, to the waterfalls at Ricketts Glen I found this large snail under some leaf litter along the wet cliff-face. I believe it to be Neohelix dentifera, the Big-tooth Whitelip. This snail seems to be close to Neohelix albolabris but is most notably differentiated by the parietal tooth. The common name "Big-tooth Whitelip" rubs me the wrong way as the parietal tooth is so small, but, as this individual measures very low on the recorded diameter size, this is perhaps a younger individual who maybe will earn the "big-tooth" portion of his name. This individual measures a width of 20.7mm and height of 10.3mm.
UPDATE: As you'll notice by the comment to this article, Neohelix albolabris can also have a parietal tooth, so apparently it's not a truly the key difference. Guess I should have read the Pilsbry species account for the similar N. albolabris before reaching my conclusion instead of just using the Burch key. However, I still think this is probably N. dentifera based on the height of the shell (as also referenced in the comment below). Mathematically it's more depressed than either measurements evidenced in Pilsbry (for N. albolabris or N. dentifera). But, since N. dentifera is the more depressed of the two, I figure it's a good bet.
|Range map from Land Snails of Limestone Communities and Update of Land Snail Distributions in Pennsylvania (Pearce) with my own county added to range (in orange). Formerly unknown to Luzerne County.|