FOSSIL SHELLS OF THE CRAG. 4G5 



Bulla olivula, Nob. Fig. 11. 



Shell cylindrical, smooth, aperture linear, spire elevated, ohtuse, separating 

 line canaliculated ? Length j, diameter ^ of an inch. 



Coralline Crag, Sutton. 



Unfortunately among thirty specimens of this shell which 

 I have found at the above locality, not more than one pos- 

 sesses the spire, and that not in the most perfect state ; there- 

 fore 1 give the characters with some degree of uncertainty. — 

 The specimen which is least mutilated has a small canal run- 

 ning round the apex, at the juncture of the upper part of the 

 body-whorl, similar to that which gives a character to the 

 genus Oliva. The specimens are much eroded at that part, 

 (a circumstance not unusual in the slender covering of the 

 sutures in many of the crag shells), independently of which 

 there appears a small canal remaining where the covering is 

 in parts perfect. 



A shell of the same size from China, in the possession of 

 Mr. G. B. Sowerby, much resembles this in having an elevat- 

 ed obtuse spire, with a canal around it, but it has a fold up- 

 on the lower part of the inner lip that I do not observe in the 

 crag species. It differs from Oliva in not having a plicated 

 columella, and in wanting the notch at the base, peculiar to 

 that genus. It more resembles, and may hereafter prove the 

 same as Bulla terebellata, pi. 1, fig. 8, 9, 10, Dubois, Conch. 

 Foss. du Plat. Wolhyni-Podolien ; but a comparison with the 

 shell is necessary for such decision. 



Three or four shells of this kind are figured by Brown in 

 his Illustrations of British Conchology, pi. 38, but as they are 

 without descriptions, it is impossible to say whether they are 

 intended for representations of shells in their natural size or 

 magnified. If they be faithfully represented, they present 

 some intermediate forms, and show the very gradual elevation 

 of the spire, which renders it so difficult to separate the spe- 

 cies, and will, I hope, afford additional evidence to justify me 

 in retaining all these shells (now figured) in the above Lin- 

 nean genus. 



With the exception of Bulla lignaria all the figures are 

 enlarged, but the natural dimensions of the specimens are 

 indicated by an annexed cross. 



