26 BULLA, DIPPER. 



what membranaceous, especially about the margin, with a 

 single minute lateral volution which is a little prominent, 

 transversely wrinkled, and covered with a silvery skin 

 tinged with pink, changeable in different positions of light, 

 and occasionally appearing nacred or with a metallic lus- 

 tre : aperture extending over the whole shell : length 

 nearly an inch and 'a half ; breadth an inch. 



It much resembles B. Plumula, but is more membrana- 

 ceons, rather more convex, with the volution more promi- 

 nent, and not placed so laterally. 



Found by Montagu, at the salt rock, in the estuary of 

 Kingsbridge, Devon : rare. 



18. Bulla fontinalis. Stream Dipper. 



Lister, pi. 134. f. 34 Da Costa, pi. 5. f. 6 Dorset Cat. 

 pi. 21. f. 6 Linn. Trans, viii. pi. 4 . f . 1. 



Shell oval, swelling, transparent, glossy, pale horn-color : 

 spires four or five, rounded and well defined, reversed, very 

 little produced ; the first very large, the others small, obtuse 

 at the point : aperture oval-oblong, reaching three-fourths 

 of the length of the shell ; the outer-lip reaching beyond 

 the base Old ones are a little wrinkled longitudinally, with 

 two or three faint transverse ridges on the body volution : 

 length half an inch 3 breadth a quarter. 



In stagnant and slow running waters, under the leaves 

 and on the stalks of plants, v. v. 



19. Bulla rivalis. River Dipper. 

 Linn. Trans, viii. pi. 4. f. 2. 



Shell oval-oblong, transparent, smooth, glossy, horn- 

 color, with five or six reversed volutions ending in a very 

 fine point : aperture oblong. It differs from B. fontinalis, 

 in being more elongated and pointed, in having the first 

 volution not so proportionately large nor tumid, and w 

 being more contracted at one end of the aperture ; and 

 from the next, in being of a more conic shape, and more 

 sharply pointed : size of the last. 



Slow streams in Hampshire, and near Nans in Ireland ; 

 rare. v. v. 



20. B.ulla Hypnorum. Slender Dipper. 



Lister, pi. 1059. f. 5JVal;ier, f. 54 Linn. Trans, viii. 

 pi. 4. f. 3 Dorset Cat. pi. 18. f. 20. 



Shell 



