EXPLANATION OF PLATE XXIII. 



Trichotropis Dalli Whitf. (p. 127). 



Figs. 1, 2. Two views of a small specimen. 



3, 4. Similar views of one of the larger shells. 

 All twice natural size. 



SCALARIA MULTISTRIATA Say (p. 126). 



Fig. 5. View of the only shell observed ; the surface is entirely exfoliated ; enlarged two diameters. 



Turritella (Mesalia) plebeia Say (p. 130). 



Figs. 6, 7. Views of two fragments. 



8. Enlargement of the lower volution of the last, showing the surface striation. 



Turritella Cumberlandia Conrad (p. 129). 



Figs. 9, 10. View of a specimen showing the upper part of the shell and an enlargement to show striae. 

 11. View of an older fragment, natural size. 



Turritella .equistriata Conrad (p. 128). 



Figs. 12, 13. Views of two specimens presenting slight variations in rate of increase. 

 14. Enlargement from fig. 13 to show striae. 



Turritella secta Conrad (p. 129). 



Figs. 15, 16. Views of two specimens, the latter preserving the striae in fairly good condition, 

 17. Enlargement from tig. 16. 



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