THE LINNEAN GENERA. 



19. NAUTILUS.— Plate 13. 



Animal, a Cephalopode ? 



Shell, univalve, spiral, multilocular, the chambers formed by transverse 

 divisions, which are concave, and communicate with each other 

 by a small tubular aperture. 



^ 20. CONUS.— Plate 14. 



•Animal, a Limax. 



Shell, univalve, convoluted, turbinated : aperture longitudinal, linear, 

 without teeth, terminated at the summit by a slope ; base entire : 

 pillar smooth. 



21. CYPRiEA.— Plate 17. 



Animal, a Limax. 



Shell, univalve, involuted, suboval, obtuse, smooth ; aperture longi- 

 tudinal, linear, toothed or wrinkled on both sides ; base strait 

 and open. 



22. BULLA.— Plate 18. 



Animal, a Limax. 



Shell, univalve, convoluted, without teeth, oval ; aperture for the most 

 part the whole length of the shell, entire at the base : often with- 

 out any spire. 



23. VOLUTA.— Plate 19. 



Animal, a Limax. 



Shell, univalve, oval, more or less ventricose, spiral : aperture sloping 

 and without a canal : pillar plaited, the lower plaits the largest 

 and most oblique. 



