CLASSIFICATION. ll 



III. UNIVALVES. 



1. With a regular Spire. 



18. Argonauta: Shell with one cell, spiral, involute. 



19. Nautilus: Shell with many cells, with a hole of 



communication. 



20. CoNus: Aperture effuse, longitudinal, without teeth. 



2 1 . C YPR^ A : Aperture effuse, linear, longitudinal, tooth- 



ed on each side. 



22. Bulla : Aperture alittle contracted, and placed ob- 



liquely. 



23. Voluta: Aperture effuse, the pillar plaited. 



24. Buccinum: Aperture with a small canal leaning to 



the right. 



25. Strombus: Aperture with a small canal leaning to 



the left. 



26. MuREx: Aperture with a small straight canal. 



27. Trochus: Aperture contracted, and somewhat 



square, 



28. Turbo : Aperture contracted and orbicular. 



29. Helix: Aperture contracted, lunate on the inner 



side. 



50. Nerita: Aperture contracted, and semiorbicular. 



51. Haliotis: Shell with a row of orifices along the 



surface. 



2. Without a regular Spire, 



52. Patella ; Shell conic, the aperture widened hke a 



basin. 



