Troxell — Unios in the Tr lassie of Massachusetts. 461 

 Fig. 1. 



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Fig. 1. Cast of Unio emersoni, n. sp. Holotype. 

 Fig. 2b. Fig. 2a. Fig. 2c. 



Fig. 2a. Diagram of same, showing outline, muscle scars, and pallial line ; 



b. Cross section of same on line AB. 

 Fig. 2c. Section through umbones of paratype. 



Fig. 3. 



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Fig. 3. £7mo emersoni, n. sp. Paratype. Showing the valves opened. 



