Illinois Natural History Survey - University of Illinois

Key to Freshwater Bivalves

Freshwater Mussels

Shell elongated, thin to moderately thick. Beak sculpture concentric.
Surface of the shell dark brown to black. Pseudocardinal and lateral teeth
poorly developed; present only as a thickened ridge. Sexual differences in 
the shell indistinct. Found in areas of reduced flow (around large boulders)
inlarge rivers with swift currents............................Cumberlandinae pp. 22-23

 

Shell usually thick and solid. Beak sculpture generally indistinct. Surface of
the shell brown, chestnut, or tan, rays or bands greatly reduced or absent.
Pseudocardinal and lateral teeth usually well developed. Sexual differences 
in the shell indistinct. Most often found in streams, but occasionally present
in lakes or large impoundments....................................Ambleminae pp. 24-73

 

Shell thin, more or less elongated. Beak sculpture usually double-looped,
occasionally concentric. Surface of the shell green, greenish brown, or black
with or without fine green rays. Pseudo- cardinal and lateral teeth absent,
reduced, or poorly developed. Sexual differences in the shell indistinct. Found 
in ponds, lakes, or the quiet-water areas of streams.............Anodontinae pp. 74-97

 

Shell relatively thin to moderately thick, rounded or oval to elongate. Beak
sculpture generally double-looped but often indistinct. Surface of the shell
mostly light yellow or tan with brightly colored rays or bands. Pseudocardinal
and lateral teeth usually well-developed. Sexual differences in the shell
apparent--squared or truncated posteriorly in females, bluntly pointed
posteriorly in males. Found in streams, occasionally in lakes or other
impoundments............................................................Lampsilinae pp. 98-171

 

Fingernailclams and Peaclams

Shell relatively small, whitish or cream-colored. Surface of the shell
covered by numerous, very fine concentric rows of elevated lines (striae).
Right valve has one cardinal tooth and two pairs of lateral teeth. Left valve
has two cardinal teeth and two lateral teeth....................Sphaeriidae pp. 172-173

 

Asian Clam

Shell small (most under 2 inches), moderately thick, rounded. Surface 
of the shell yellowish brown to black, with numerous, evenly spaced, 
concentric, elevated ridges. Three cardinal teeth in each valve located 
below the umbo; two sets of serrated lateral teeth in each valve, paired 
on each side of the umbo in the right valve, single on each side in the left.
Introduced into western North America in the 1920s and 1930s and spreading 
throughout the United States.....................................Corbiculidae pp. 174-175

 

Zebra Mussel

Shell small (most under 1 inch), moderately thick, triangular, and more
or less elongated. Surface variably banded with black or brown and cream
stripes. Introduced into the Great Lakes in the 1980s and spreading to large
rivers and lakes throughout the United States................Dreissenidae pp. 176-177


 

 

Created 6/9/1995 Last Modified 1/10/2002 cam



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