Virginia Land Snails

Photo(s): A putative Mesodon clausus shell by Larry Watrous ©.

Click photo(s) to enlarge.

Mesodon clausus (Say, 1821)

Family: Polygyridae
Common name: Yellow Globelet

Width: 13.6 - 18.0 mm
Height: 10 - 13 mm
Whorls: 5+

This snail has a globe-shaped shell, and a slit-like umbilicus partly covered by the reflected peristome. There are no teeth in the aperture. The shell surface is finely and closely striate. The shell is very similar to that of M. thyroidus, though usually smaller and lacking a parietal tooth. Mesodon clausus may be a spurious description of M. thyroidus colonies living in calcium-poor habitats, resulting in smaller toothless shells.

Like M. thyroidus this snail is patchy in distribution, and often along river floodplains and wetlands.

Emberton (1991) found a close relationship between M. clausus and M. thyroidus but claimed a small shift in reproductive anatomy and allozymes. Synonyms for this species include Mesodon clausa, Helix clausa, H. ingallsi, H. jugallsiana, Triodopsis thyroidus edentula, Polygyra clausa.

Mesodon clausus is distributed in the southern, midwestern and eastern United States, sympatric with the range of M. thyroidus. It is reported in western Virginia counties.

NatureServe Global Rank: G5;
NatureServe State Rank: S2S4
Virginia’s wildlife action plan: Tier IV


Ken Hotopp 4/2013

Range Map