EXPLANATION OF THE PLATES AND WOOD-CUTS. 



Fio-. 13. Unio centralis. Transversely oval, rather convex ; beaks nearly central. 



Length 11 lines, width 17 lines. 

 Fig, 14. Unio robustus. Obovate, convex, strongly marked with lines of growth, 

 nearly as long as wide ; posterior extremity rather pointed. 

 Length 1 inch 5 lines, width nearly If inch. 

 Fig. 15. Modiola carinata. Obliquely elongated ; valves boat-shaped, deep ; anterior 

 lobe small. 



Length 11 lines, width more than i an inch. 

 Fig. 16. Mytihis triangularis. Triangular, with a rounded front, rather flattened, 

 keeled towards the beaks. 



Length 11 lines, width about 9| lines. 

 Fig. 17. Avicula quadrata. Quadrangular, convex, keeled; anterior lobe small, 

 pointed ; front rounded. 



Length about an inch, width nearly the same. 

 Fig. 18. Avicula modiolaris. Obliquely elongated, compressed ; keeled towards the 

 beaks ; anterior lobe pointed. 

 Length 8 lines, width 4^ lines. 

 Fig. 19. Pecten gentilis. Oblong, convex, smooth, with 15 slightly-elevated rays, 

 which are alternately long and short ; ears middle-sized, equal. 

 Length 5 lines, width 5 lines. 

 A small neat shell. 

 Fig. 20. Pecten scalaris. Oblong, convex, concentrically striated, radiated, radii about 

 15, acute. 



Length 6 lines, width 5 lines. 

 Fig. 21. Spirifera bisulcata, (M. C. t. 494.) This specimen shows the impressions of 

 the internal spiral appendages, which, together with the long hinge-line, charac- 

 terize the genus Spirifera. 

 Fig. 22. Globulus vetustus. Globose, smooth ; spire pointed ; umbilicus very small, 

 open. 



Height 1 1 lines, diameter 9 lines. 

 Fig. 23. Littorina ? obscura. Oblong, umbilicated ? smooth ? spire elevated ; whorls 

 rather flattened on the sides. 

 Height 14 hnes, diameter 10 hues. 



The specimens are imperfect casts ; they resemble the L. litlorea, but are more 

 elongated and have the whorls more distinct. 

 Fig. 2\'. Turritella ? clavata. Turreted, conical, smooth ; whorls about 8, flat. 

 Height 10 lines, diameter 5 lines. 



This being only part of a cast, the genus cannot be ascertained with certainty. 

 Fig. 25. Turritella? minima. Turreted, conical, ribbed; ribs obtuse, about 16 to 

 each whorl ; whorls about 10. 

 Height 7 lines, diameter 2^ lines. 

 /'V^>-. 26. Poli/jihetnus? fusi/onnis. Fusiform, smooth ; aperture half the length of the 

 shell, narrow ; columella curved ? 



Height about 2| inches, diameter above an inch. 



