EXPLANATION OF PLATE XIIL 



DioNE Marylandica Conrad (p. 74). 



1. Copy of Mr. Conrad's figure ol' the species from the Miocene Fo.ss., PL ix, fig. 1. 



UOSINIA ACKTABULUM Couriul (p. 73). 



2. Copy of Mr. (JouriKl's figure of the shell from Mioceue Koss., PI. .\vi, fig. 1. 



Artenia staminea Courad (p. 72). 



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

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



H, 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. 



170 



