Charlie and others,

On a statewide rather than continental scale, here are largest and smallest
Wisconsin mollusks.

The largest gastropods are both introduced species, Bellamya chinensis
(freshwater) and Helix pomatia (terrestrial), with measured heights of
Milwaukee Public Museum specimens at 55.1 mm for the first and 35.1 mm for
the second.  The largest bivalve is Lasmigona complanata, length 193 mm
(Baker 1928).

The smallest freshwater gastropod is Gyraulus circumstriatus, with Baker
(1928) giving 1.0 mm for a G.c.walkeri subspecies in the state.  The
smallest terrestrial gastropod is Punctum minutissimum at 0.7 mm.  The
smallest bivalve is Pisidium simplex, which Baker (1928) called a
subspecies of punctatum but Korniushin et al. (2001) raised to full species
level, at 1.6 mm.

Joan

J.Jass, Milwaukee Public Museum, Milwaukee WI USA, email: [log in to unmask]