EXPLANATION OF PLATE XX. 



AVBLLANA BULLATA Morton (p. 163). 



Figs. 1,4. Views of two different specimens, apparently both used by Dr. Morton. Aoad. Nat. Soi., 

 Phila. 



CiNULiA ovoiDEA Gabb (p. 162). 



5, 6. Two views of Mr. Gabb's type specimen. 



Bulla Mortoni Lyell &. Forbes (p. 165). 



7, 8. Front and back views of a very large specimen from Crosswicks, in the Columbia College 

 collection. 

 9. View of a smaller specimen. Collection Acad. Nat. Sci., Phila. 



Cyhchna kecta Gabb (p. 164). 



10, H. Two views of the type specimen enlarged two diameters. 



Dentauum (Falcdla) falcatum Conrad (p. 169). 



12, 14. View of stnaU much curved specimen, all casts. 

 15-17. Views of the larger portion of three individual oasts. 



16. Portion of a partial cast, looking on the back and showing striae of growth. Acad. Nat. 

 Sci. Phila. 



Dentalium subarcuatum Conrad (p. 166). 



19. View of a crushed shell from Haddonfleld, New Jersey. 



20. View of a shell showing the curvature. 



21,22. Opposite sides of casts showing the internal features described. 



23,24. Enlargement of the surface of Pig. 19, and transverse section of the same. Acad. Nat. 

 Sci., Phila. 



Bbrpula (Diploconcha) cretacea Conrad f (p. 170). 



25. View of the specimen described showing the general features. 

 338 



