46*2 FOSSIL SHELLS OF THE CRAG. 



truncated, leaving the spire visible, though depressed, with a 

 slight compression around the upper part of the body-whorl. 

 The whole marked with strice diverging from the summit. 



Bulla dilatata, Nob. Fig. 3. 



Shell subcylindrical, vertex truncated, spire depressed, visible, aperture 

 large, expanding towards the base ; striated, strice diverging, muscular 

 impression large. Length f, largest diameter 7 | of an inch. 



Coralline Crag, Sutton. 



The spire is visible although depressed, the upper part of 

 the whorls convex, producing a deep suture or subcanal round 

 the vertex. The aperture is much expanded, showing the 

 muscular impression imperfectly divided, being deeply seated 

 around the base, and slightly visible along the edge of the 

 outer lip, and again deeply impressed at the upper part. — 

 The striae are visible at the apex, running round the convo- 

 lutions of the shell, but diverging towards the base, where 

 they are almost at right angles with those above. Under a 

 lens it shows externally a very elegant chain-like appearance, 

 produced by small oval depressions, similar to those of Bul- 

 la catenata : it has a slight depression behind the thickened 

 edge of the inner lip, running to the base. 



A recent shell from the coast of Bute, given to me by Mr. 

 Lyell, is perfectly identical with the above ; but in its recent 

 state is beautifully transparent, the chain-like strice being vi- 

 sible on the inside. 



Bulla lignaria, Auct. Fig. 4. 

 Shell ovate, thin, spirally striated, vertex depressed, aperture wide. 

 Coralline Crag, Ramsholt and Sutton. 



Four or five entire specimens, with a few fragments suffi- 

 cient to allow of a careful comparison, have enabled me to 

 decide upon the identity of this shell with the well-known re- 

 cent species. Nothing that I could imagine to be the testa- 

 ceous gizzard, or even a part of it, has ever come under my 

 observation. I have only one fragment from the red crag, 

 but its tenuity is ill adapted to withstand the bouldering of a 

 littoral deposit, and also its comparative rarity in the coral- 

 line crag may account for its non-appearance in the upper 

 bed. 



Bulla ventrosa, Nob. Fig. 5. 



Shell ovate, globose, striated, spire concealed, aperture suboval, extending 

 to the apex, narrow above, expanding towards the base, umbilicated. — 

 Length 7 |, diameter ^ of an inch. 



Coralline crag, Sutton. 



