BULLA-- DIPPER. 75 



its having swallowed entire a shell nearly equal 

 in size to itself; not unfrequently shells are 

 found in their gizzard, reduced to a powder, 

 affording ample proof that it unites the two 

 offices of mastication and digestion. 



The Bullae are not furnished with an oper- 

 culum ; indeed to many of the species it would 

 be a useless appendage, as the animal extends 

 beyond the shell, and cannot, on account of its 

 gizzard contract itself so as to retire within. 

 The marine species also reside in deep water, 

 and they are as safe there from crabs and other 

 enemies as the mollusks who live near the shore, 

 and barricade the mouth of their shells with their 

 opercula. 



BULLA Lignaria* 



WOOD DIPPER. 



Specific Character. Shell oval, thin, brittle, 

 semi-transparent, yellowish or chesnut brown, 

 with numerous transverse striae of a light colour 

 approaching to white, giving it some resem- 

 blance to veined wood ; sometimes it has one or 

 two oblique bands ; inside white, glossy ; aper- 

 ture large, extending the whole length of the 

 shell, somewhat contracted towards the upper 

 part ; columellar lip smooth ; it has no external 



* Plate II. fig. 6. 



