THE LINNEAN GENERA. xi 



19. NAUTILUS.— Plate 13. 



Animal, a Cephalopode ? 



Shell, univalve, spiral, multilocular, the chambers formed by trans- 

 verse divisions, which are concave, and communicate with each 

 other by a small tubular aperture. 



20. CONUS.— Plate 14. 

 Animal, a Limax. 



iS/te//, univalve, convoluted, turbinated; aperture longitudinal, linear, 

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

 pillar smooth. 



21. CYPR/EA.— 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 

 without 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. 



