214 POPULAR BRITISH CONCHOLOGY. 



upwards and downwards^ as if beating tlie water, with con- 

 siderable quickness ; and that, although he could not dis- 

 cover in this species the shelly plates which compose the 

 gizzard in most of the species of the Bullcea, yet the giz- 

 zard must exist in every case, whether shelly or horny in its 

 texture. 



YII. Bulla. — The true Bidlm of the authors of the 

 ' History of British Mollusca' belong to the genus Hami- 

 nea of Arthur Adams, as described in my ^ Thesaurus.^ If 

 the views of the latter author should be adopted, we must 

 arrive at the conclusion that no representativ^es of the true 

 Bullce honour our coasts with their presence. 



Our plan being however in this work to adopt implicitly 

 the arrangements of the ' History,^ we describe the remain- 

 ing British species of the family as Bulla Hydatis and Bulla 

 Cranchii. 



B. Hydatis has a general aspect not unlike that of Philline, 

 the animal covering the shell in the fold of its mantle, 

 and the side lobes, when folded, meeting over the back. 

 It is thick and slug-like, of a greenish-yellow tint, 

 speckled minutely with brown, black, and yellow. The 

 head-lobe is large, with eyes slightly projecting towards 

 the middle of the disc ; the foot is rather square, and 



