97 



BULLA. 



A. Birostrate, or produced both ways. (Plate 



XIV. %. 5.) 



B. Caudate, (fig. 6.) 



C. Without any elongation, (fig. 7.) 



D. Tapering, (fig. 8.) 



Shell univalve, convolute, unarmed. Aperture 

 subcoarctate, oblong, longitudinal, entire at the 

 base. Columella oblique, smooth. 



The diagnosis of this genus is, perhaps, least 

 accurately determined of any. Some species ap- 

 proach so nearly to Cypraea, others to Helix, to 

 Buccinum, or to Murex, that it is very difficult to 

 trace out the line of demarcation. The most com- 

 mon character of Bulla is an inflated egg-shaped 

 body ; and it will be found to differ from those ge- 

 nera which it most resembles, in some one, if not 

 in more essential points. 



To render this genus in some degree more sy- 

 stematical, it is proposed to apportion it into the 



H 



