Land Snails

Photo(s): The domed shell of Discus patulus, © Larry Watrous.



Illustrations © Kathy Schmidt from her series "Land Snails of New York State."

Click photo(s) to enlarge.

Discus patulus (Deshayes, 1830)

Family: Discidae
Common name: Domed Disc

Identification
Width: 8.0-8.9 mm
Height: 3.3–4.0 mm
Whorls: 5

The shell of this disk is mostly flattened, with rounded, tight whorls, and a tiny basal lamella. It is notable for its very wide umbilicus and shallow-domed apex. It is usually light reddish-brown in color, with coarse but regular radial ribbing.

Ecology
This species is sometimes found in deep layers of moist leaves, but more commonly on stumps and old logs in mature or late-successional forests. It is often patchy in distribution, with colonies around rotting woody debris. In Tennessee, its occurrence was correlated with increasing slopes, damper soils, and higher soil pH (Coney et al, 1982).

Taxonomy
Synonyms for D. patulus are: Discus patulus angulatus, D. p. carinatus, Helix patula, H. perspectiva, Goniodiscus patula, Gonyodiscus perspectivus, Patula perspectiva, and Pyramidula (Gonyodiscus) perspectiva.

Distribution
This snail is found very widely across most of the eastern US and southern Ontario, though it does not enter Maine or Florida. Its range in Virginia covers the western, central, and south-western parts of the state.

Conservation
NatureServe Global Rank: G5

 

Greg Kimber, Ken Hotopp, Meegan Winslow 8/2012

Range Map (click to enlarge)