GASTEROPODA. 95 



elevated, numerous, transversely crossed by others of nearly equal size j and interstitial 

 spaces deep. 



The anterior sulcus has a hollowed or spoon-shaped figure, and, like the other portion 

 of the surface, is cancellated ; but the longitudinal ribs are more closely arranged i the 

 number of ribs in the circumference is about 50. 



Height 3 lines, basal diameter 6 lines, width of anterior sulcus at the margin 2 lines. 



Locality. It is very rare, and has been obtained only in the white stone of Eastcombs 

 and Bussage : we are not aware that more than three examples have been found. 



Umbrella? Hamptonensis. Plate XII, figs. 12, 12«. 



XI. Testa parvd, depressd; ambilu orbiculari; apice obtuso, depresso, cenfrali; costis 

 radiantibus, lavibus, paucis, irreyularibus, Jlexuosis ; sulcis inter stitialibus separatis. 



Shell small, depressed; base orbicular; apex obtuse, discoidal, and central; ribs 

 radiating, smooth, few, irregular, and waved ; separated by interstitial sulcations. 



This little shell is sometimes perfectly flat, but usually somewhat convex ; it is 

 extremely thin, and as the under surface has not been fully disclosed, it must be referred 

 to Umbrella with some degree of doubt; it may, however, be probably considered as 

 related to the patelliform shells. The basal diameter rarely exceeds 4 lines. 



Locality. The soft shelly Oolite beneath the planking usually furnishes it in the 

 neighbourhood of Minchinhampton : it is rare. 



Order — Opisthobranchjata, M. Edwards. 

 Family — B u lli t>je . 



Bulla, Linn. 



Shell oval, ventricose, or cylindrical, generally thin and fragile, the last whorl more or 

 less enveloping the preceding ones ; spire umbilicated, or slightly produced ; aperture 

 large, the whole length of the shell, narrow above and dilated below ; outer lip sharp. 



The specimens of this genus from the Great Oolite are very few, and in a condition less 

 satisfactory than could be wished. They have been obtained (with a single exception) from 

 the upper beds of the formation to the east of the town of Minchinhampton. These beds 

 usually consist of hard gray or brownish calcareo-siliceous sandstones, sometimes con- 

 cretionary, and contain Ceromya, certain Pholadomya, and other shells which are never 

 found in the lower and more shelly beds. The Bulla are rare, but might possibly become 

 less so, were the stone brought more under the inspection of workmen and connoisseurs ; 

 but being lifted only in small quantities during the winter season, from little excavations 



