85 
BULLA. 
A. Birostrate, or produced both ways. (Plate 
XIV. Fig. 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 
genera which it most resembles, in some one, if 
not in more essential points. 
To render this genus in some degree more sys- 
tematical, it is proposed to apportion it into the 
four divisions, of which the forms are given in the 
plate of Bulla. Though some, even many of the 
