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"The fresh-water mussel...the outside of the shell (right valve)...u., The umbo; L., the ligament; l.g., a line of growth; A., anterior (the blunter end); P., posterior; V., ventral." -Thomson, 1916

Freshwater Mussel

"The fresh-water mussel...the outside of the shell (right valve)...u., The umbo; L., the ligament; l.g.,…