Taken primarily from Kozloff, 1987, 1996 (Copyright 1987, 1996, University of Washington Press. Used in this web page by permission of University of Washington Press)
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| Lower taxonomic level | Main Page | Alphabetic Index | Systematic Index | Glossary |
| 1a | Shell attached to the substratum by its right valve; shell white, sometimes with red or green markings; concentric lamellae often raised up into spinelike projections (not likely to be found north of Oregon) | Pseudochama exogyra |
| 1b | Shell attached by its left valve; exterior waxy-translucent, sometimes with pink or red streaks; concentric lamellae close-set, generally foliaceous | Chama (Chama) arcana |