EXPLANATION OF THE PLATES: YOL. I. 



Plate 1. 



FIGUEB. PAGE. 



1. Structure of shell of Cyprsea Mauritiana, 235 diam. 



(Keferstcin), . . . . . . . . 16 



2. Polished surface of pearly layer of Pinna nigrina, 85 



diam. (Keferstein i, ...... 16 



3. Section of Pinna nigrina, showing rhombohedral crystals. 



(Keferstein), ' . . 16, 18 



4. Aragonite crystals on the inner side of pearl}'' layer of 



Pinna nigrina, 360 diam., . . . . . 16 



5. Terebratula. Section. . . . . . . 18 



6. 7. Sections of Conus ponderosus, Brug. Miocene of 



Touraine ; a, outer layer ; &, middle ; c, inner la^^er : 



(Z, e,/, lines of growth. (Woodward), ... 18 



8. Section of Conus perforated bj' Lithodomi. (Wood- 



ward), 13 



9. Meleagrina margaritifera, Linn., with pearls. (Chenu's 



Manuel) 16 



10. Dipsas plicata. Leach, interior surface, showing artifi- 



ciall}' produced pearls, simulating gods. Specimen. 17 



11. Csecum, showing stages of growth. (Fischer.) a, spiral 



embryonal shell ; 6, c, first and second partitions ; d, 

 aperture, . . . . . . . . . 23 



12. 13. Eucalodium Liebmanni, Pfr. (Fischer.) a, adult 



truncated shell ; b, the deciduous spiral earlier shell, 23 



14. Auricula Judae, Linn. Section showing the absorption 



of the interior walls of the volutions. (Fischer's 

 Manuel, fig. 21), 23 



15. Cymba proboscidalis. Lam. Showing the irregular, large 



callous nucleus, . . . . . . . 15 



16. Helix carocolla, Linn. Scalariform. Specimen, . 24 



17. Helix aspera, Miiller. Scalariform, .... 24 



18. Planorbis marginatus, Linn. Scalariform, . . 24 



Plate 2. 



19. Section of shell of Belemnites. Showing the pro- 



ostracum, rostrum and phragmocone, . . 28, 30 



20. Pro-ostracum of Belemnites Puzosianus, ... 30 



21. Pro-ostracum or anterior shell of Belemnites, . . 30 



22. Pro-ostracum of B. hastatus, ..... 30 



(297) 



