478 BULLA. 



This shell rarely exceeds half an inch in diameter, and is thin, 

 pellucid, white, very brittle, and without any external con- 

 volution or umbilicus; the aperture is so extremely large, that 

 the whole shell lies open to view, except a small part, where 

 the inner lip is slightly involuted. Unlike all other shells, ex- 

 cept those of a few congenerous species, it is not a testace- 

 ous covering, but is so completely enveloped by the animal, 

 that not the least trace of it can be discovered, and it is there- 

 fore more aualogous to what is called the shield of a Laply- 

 sia. In Lamarck's System it forms a genus which he has 

 placed among the Naked Mollusca, with the name of Bull tea, 

 but he does not appear to have been aware that it had before 

 received a similar arrangement from other authors. Gmelin 

 has described it as Bulla aperta among the Testacea, and 

 also under Muller's name of Lobaria quadriloba among the 

 Mollusca, without any intimation that they are the same. 

 Masticatory organs, similar to those of Bidla ligtiaria, 

 have been discovered in this species by Mr. Montagu. 



catena. 15. Shell oval, minute, pellucid, trans- 

 versely striated ; spire obtuse ; aperture very 

 large. 



Bulla Catena. Montagu Test. p. 215. t. 7. f. 7- Matoti 

 and Racket in Lin. Trans, viii. p. 122. 



Inhabits the coasts of Devonshire. Montagu. 



Shell rarely exceeds one-tenth of an inch in diameter, white,, 

 glossy, pellucid, finely striated all over, and in shape much 

 like B. aperta. Mr. Montagu has observed that under a 

 strong magnifier the striaj appear interwoven or formed into 

 links like a chain; apex obtuse, with a visible involution. 



plumula. 16. Shell ovate-oblong, depressed, wrin- 

 kled concentrically, and the aperture very 

 large. 



Bulla Plumula. Montagu Test. p. 214. t. 15. f. 9, and 

 Vign. 2. f. 5. Maton and Racket in Lin. Trans, viii. 

 p. 123. 

 Inhabits the coasts of Devon, on Milton Sands. Montagu. 

 Shell half an inch long and only half as broad, pellucid, thin, 

 of a yellowish colour tinged with brown at one end, and the 

 other end slightly convoluted ; it is strongly wrinkled concen- 

 trically, and marked with two or three ray-like indentations 

 running from the margin towards the apex. This shell is 



