464 FOSStL SHELLS OF THE CRAG. 



Coralline Crag, Sutton. Abundant. 



In Montague's description of this shell it is stated to be 

 smooth, with considerable gloss, as it is also in Fleming's 

 British Animals, p. 293 ; no mention is made of its having 

 stria. Nine out of ten of those from the crag are so much 

 eroded as not to show them, but they are very visible in per- 

 fect specimens ; this, however, is the case with the recent 

 shells, it is only in some specimens that the strice can be there 

 seen. The recent shell appears in general to be rather more 

 cylindrical, but it corresponds in all other respects. 



Bulla subtruncata, Nob. Fig. 9. 



Shell cylindrical, smooth, aperture linear, slightly expanded at the base, 

 vertex depressed, visible. Length, ^, diameter -^ of an inch. 



Coralline Crag, Sutton. 



This differs from the young of Bulla cylindracea (for which 

 perhaps it might be mistaken) in having the spire visible al- 

 though depressed ; it has a slight contraction in the upper 

 part of the body, which gives an apparent expansion to the 

 lower part of the outer lip. The whorls are carried rather 

 above the spire, causing it to be depressed, but distinctly vi- 

 sible ; outer lip nearly straight ; no striae to be seen in any 

 of my specimens, however, that may be from erosion or de- 

 composition. 



It appears intermediate between Bulla cylindracea and 

 Bulla obtusa, differing from the former in having the spire 

 visible, and from the latter in being longer and more slender. 

 I am induced to consider it a distinct species, having twenty 

 specimens presenting the same characters ; there is a possi- 

 bility of its being the young of cylindracea, with a visible 

 spire, only that shell is never contracted in its whorls. 



Bulla obtusa. Fig. 10. 



Bulla Regulbiensis, Turt. Linn. iv. p. 351. 



„ minuta, Woodward, Geol. of Norf. tab. 3, fig. 3. 



Shell subcylindrical, aperture linear, widening at the pillar, outer lip slight- 

 ly incurved, vertex elevated, obtuse. Length, tj, diameter ^ of an inch. 



Mammaliferous Crag, Bramerton. 



This shell, I believe, is peculiar to the newest bed, at least 

 I have never seen it from either the red or coralline crag. — 

 The spire of the fossil does not appear, from the few speci- 

 mens I have seen, to be quite so elevated as that of the recent 

 shell. 



