Drop Snails (Family Helicinidae) 

Globular Drop snail (Oligyra orbiculata Say, 1818)

Drop snails have a notable shape – like little "globs". Two species are named in the databases: the Cherrystone Drop snail, Hendersonia occulta (Say, 1831), and the Globular Drop snail Oligyra (Helicina) orbiculata Say, 1818.

There were two collections of the Cherrystone Drop snail from the opposite sides of the state along the southern border (several from Posey County up to the 1950s and one in Delaware County). There was a single recent collection (2015) of the Globular drop in Bartholomew County.

Dourson (2010) describes the structure and habitat of the drop snails in Kentucky which might work for Indiana. The Globular and Cherrystone Drops are about the same size, but the Globular drop has a rounded periphery (see image) and a light brownish band (may  not always be there according to Oesch et al. 2013) . 

While both species are calciphiles, the Cherrystone Drop favors "river bluffs, mixed hardwood talus slopes, ravines and mountainsides" while the Globular Drop is found in "more open habitat such as glades and limestone areas".  It is also noted as a glade species in Missouri (Oesch et  al. 2013).


Oesch et al. (2013) gives a key to distinguish the species, modified here:

Cherrystone Drop snail

Hendersonia occulta (Say, 1831)

Globular Drop snail

Oligyra orbiculata Say, 1818