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113. Unio rubiginosus Lea. Common in the river and 



in the Ohio canal; in the latter a peculiar form 

 with the valves flattened; nacre milky white to 

 salmon colored. Some specimens ressemble closely 

 the following. 



114. Unio coccineus Hild. Rather common in the river; 



variable; nacre white, or salmon colored, to deep 

 pink. The larger specimens have constantly some 

 undulations below their middle. 



115. Unio pyramidatus Lea. River, not common; some 



specimens very large; nacre white to deep pink 

 colored. 



116. Unio subrotundus Lea. River, very common; de- 



cidedly variable. In some specimens the beak^ are 

 very prominent, even so that extreme forms closely 

 ressemble U. pyramidatus, while others are hardly 

 distinguishable from large U. coccineus; the soft 

 parts, however, and also the nacre are characteris- 

 tic enough to separate them. The following are the 

 most remote from the type: 



a. var. kirtlandianus. Rather thin, flat, with the 



outline somewhat subquadrate. 



b. var. . With remarkably regular, rather strong 



striae of growth; found only in some localities, and 

 little connected with the type; the beaks are very 

 massive and in some exs. quite anterior. 



117. Unio aesopus Green. River, rare at New Philadel- 



phia; frequent two miles above Canal Dover; little 

 variable. 



118. Unio clavus Lam. River, not common. 



119. Unio pustui.osus Lea. River, common; variable; 



some specimens are almost covered with warty 

 prominences, while others show scarcely a trace of 

 them; some are much inflated, others very little so. 

 All four branchiae are charged with embryones, as 

 in the other species of the group. 



120. Unio verrucosus Barn. River, scarce, large. 



121. Unio undulatus Barn. River and Ohio canal, com- 



mon. Some specimens show only traces of the un- 

 dulations, while in others they are very pronounced. 



