GASTEROPODA. 101 



Cylindrites brevis. Plate VIII, figs. 13, 13a, b. 



C. Testa parvd, cylindro-truncatd, apice amplo, piano, margine acuto ; lateribus plants ; 

 aperturd ad basin sub-expanso. 



Shell small, truncated, cylindrical, vertex large, flattened, its margin acute ; sides of 

 the shell flattened, marked with lines of growth ; aperture moderately expanded towards 

 the base. 



This is the most truncated species of the genus in the Great Oolite. The vertex is 

 very wide, almost perfectly flattened ; but the acute edges of the volutions are visible, and 

 likewise the minute mamillary apex. These characters, together with the short figure, 

 serve to distinguish it from C. cylindricus, Plate VIII, fig. 19, the shell which most nearly 

 approaches to it. Axis 5 lines, diameter of vertex 3 lines. 



Locality. Minchinhampton Common, where it is very rare. 



Cylindrites Thorenti, Buviyn., sp. Plate VIII, figs. 22, 22#, b, c. 



Bulla Thorentea, Buvignier. 1842. Geol. des Ardennes, p. 535, t. v, fig. 9. 



— — Buvignier. 1843. Me'm. Soc. Philom. Verd., ii, t. 5, fig. 11. 



— — WOrb. 1850. Prod. Paleont., p. 304. 



— elongata, Thorent. Mem. de la Soc. Geol. de France, iii, p. 258. (Not 



Phillips, Geol. of Yorkshire.) 



C. Testa subcylindricd, lateribus convexiusculis, spird parvd, depressd, contractd; anfrac- 

 tuum marginibus solum exsertis; aperturd angustd, columella ad basin uniplicatd. 



Shell subcylindrical, the sides somewhat convex, smooth, or slightly marked by the 

 lines of growth ; spire small, depressed, and contracted ; the whorls with their margins 

 only visible ; aperture narrow, basal fold of the columella large. 



The apicial excavation is more contracted than in either of the other species ; the apex 

 is large, but does not rise quite so high as the outer margin; the shell, in its general figure, 

 is elongated and contracted at both the extremities. Axis 9 lines, greatest transverse 

 diameter 4 lines, diameter of the terminal excavation 1 line. 



Locality. Minchinhampton Common ; it occurs in the bed of planking, but is 

 very rare. 



M. A. Buvignier states that this fossil is found in the white limestone of the Great 

 Oolite in the environs of Rumigny. M. Thorent has also found it near Aubenton, and 

 mentions it in the Memoir above referred to, under the name of Bulla elongata, as 

 occurring in the Coral Rag ; this is considered to be an error by M. Buvignier, as the bed 

 containing it, in following its course into the Ardennes, is undoubtedly beneath the 

 Oxford Clay. 



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