THE LINNEAN GENERA. xi 



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. CYPRjEA. 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. 



