BULLA DIPPER. 75 



bed, the ribs terminating within the lips ; of a 

 pale purple or flesh colour, with three dark spots 

 on the ridge of the back. 



This is a British species, and found abun- 

 dantly on our shores ; it greatly resembles the 

 West Indian species, but is distinguished from 

 it, in having no dorsal groove, and the dorsal 

 spots, if there are any, being limited to three. 

 Both the shell and the inhabitant vary so much 

 in their different stages of growth, that much con- 

 fusion has arisen in their classification. The 

 shell in its juvenile state is extremely thin, 

 brittle, pellucid, and quite smooth ; and the ani- 

 mal of a pale colour, displaying no reflected 

 membrane. In its adult state the shell is thick, 

 opaque, ribbed, and the animal extends over it 

 the lateral appendages of its mantle, which are 

 speckled with a variety of colours, giving a beau- 

 tiful appearance to the animal when in motion 

 under the water 



GENUS. BULLA.* 



DIPPER OR WATER BUBBLE. 



Generic character. Shell univalve, convo- 

 luted, often without any spire, smooth ;| shape 

 suboval, inflated ; aperture longitudinal, generally 

 the length of the shell, entire at the base, con- 

 tracted ; columella oblique, smooth- 



Plate II. fig. 6, 9, 9. 



fTheBulke are said to be smooth, because their surface has 

 never any projections. 



