EXPLANATION OF PLATE IV. 



Pecten Madisonius Say (p. 30). 



FiGS. 1, 2. Views of young right and left valves. 



3. Fragment of a larger valve. 



4. A still larger shell with the anterior ear lost. 



5. A copy of Conrad's figure of this species, taken from his Miocene Foss., PI. XXIV. 



Vola Humphreysi Conrad (p. 32). 



Fig. 6. View of a small lower valve. 

 7. A larger upper valve. 

 8, 9. Outer and inner faces of a fragment of a large upper valve. 



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