Fics. 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., Pl. xxtv. 
Fic. 
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. 
EXPLANATION OF PLATE IV. 
PECTEN MADISONIUS Say (p. 30). 
Vota HuMPHREYSI Conrad (p. 32). 
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