EXPLANATION OF PLATE VI. 



Mytiloconcha incrassata Conrad (p. 38). 



Figs. 1,2. Views of a specimen from South Carolina, introduced to show the general form. [Am. 

 Mus. Nat. Hist.] 



Modiola inflata Tuoiney and Holmes (p. 39). 

 Fig. 3. View of the right side of a well-preserved specimen. 



4. View of a distorted internal cast from the Brown clays. 



Arca (Striarca) centenaria Conrad (p. 42). 



Figs. 5, 6. Exterior and interior views of a specimen of small size, although the largest perfect one 

 seen from the State. 

 7. Enlarged view of the hinge, showing the peculiar structure of the teeth. 



Arca (Scafharca) callipleura Conrad (p. 43). 



Fig 8. A copy of Mr. Conrad's figure, Miocene Foss., PI. xxix, fig 2. 



9. View of the only fragment seen from New Jersey. 



Arca (Scapharca) lienosa Say (p. 44). 



Figs. 10, 10a. A copy of Say's original figure, no fragments from New Jersey being perfect enough to 

 figure. 



Arca (Scapharca) subrostrata Conrad (p. 45). 



Fig. 11. Copy of Conrad's figure, Miocene Foss., PI. xxx, fig. 7. 



12, 13. Two of the fragments obtained from the well-boring at Atlantic City, N. J., where the 

 remains of the above two species were also obtained. 



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