James,
Rumina decollata is a little land snail, about an inch long, slender and
elongate, not rounded like a Helix or flattened like a Polygyra.  It is is
glossy, translucent, tan colored, and it would be shaped like a plump little
auger shell, except for one feature.  As its name indicates, it is always
decollate, that is the upper several whorls of the spire are always missing,
giving it a "sawed off" appearance.
Paul M.