CATECHISM OF CONCHOLOGY. 53 



necessary to observe, that as some species of 

 Bulla approach nearly to Cypraea, Helix, Buc- 

 cinum, or Murex, the most distinguishing charac- 

 teristic is an inflated egg-shaped form. The name 

 Bulla, a bubble, is descriptive of the peculiarity 

 which characterizes the real offspring of the 

 Bulla family. 



CHAP. XXVI. 



UNIVALVES: 

 VOLUTA ; Volute, or Wreath. 



Q. How am I to distinguish the genus Voluta ? 



A. By observing the shell is spiral, somewhat 

 effuse, without a beak ; and that the pillar is 

 twisted or plaited, generally without lips or per- 

 forations. 



Q. Does not this genus contain many appa- 

 rently incongruous shells ? 



A. It does so, but yet still it is easily discri- 

 minated, because all shells are referred to it 

 which possess a plaited columella. 



Q. Is not the Voluta Pyrum, or pear-shaped, 

 a valuable shell ? 



A* It is held sacred in China, and every pa- 

 E 3 



