EXPLANATION OF PLATE XIII. 

 Dione Marylandica Conrad (p. 74). 

 Fig. 1. Copy of Mr. Conrad's figure of the species from the Miocene Foss., PI. ix, fig. 1. 



Dosixia acetabulum Conrad (p. 73). 

 Fig. 2. Copy of Mr. Conrad's figure of the shell from Miocene Foss., PL xvi, fig. 1. 



Artenia staminea Conrad (p. 72). 



Figs. 3. View, natural size, of a small left valve. 



4, 5. Two views of the same shell, twice enlarged. 

 6, 7. Opposite sides of a mature right valve, natural size. 

 9, 10. Two views of the valves together, figs. 6 and 7 being of -one of them. 



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