GASTEROPODA. 53 



Shell turreted, turbinated, acute ; whorls (6 — 7) convex and costated ; costae oblique, 

 directed from right to left. 



The costse are rather more elevated than in R. acuta, and the entire figure is more 

 turbiniform, the whorls being much more convex. Length from 2^ to 3 lines. 



Locality. Ancliff ; also very rarely at Minchinhampton Common, in the planking. 



Rissoina acuta, iSow. Plate IX, fig. 9. 



Rissoa acuta, Sow. 1829. Min. Con., t. 609, fig. 2. 



— — Brown. Illust. Foss. Conch., p. 79, t. 38, figs. 25, 26. 



— — Bronn. Index Palseont., p. 1090. 

 Rissoina acuta, D'Orb. Prod. Paleont., p. 297. 



R. Testa parvd, turritd, acuta; anfractibus convexiusculis 6, costulis angustatis subre- 

 motis longitudinalibus; aperturd ovatd; labio dextro expanso. 



Shell small, turreted, acute ; whorls (6) slightly convex, with narrow, rather remote, 

 longitudinal ribs ; aperture oval ; right lip expanded. 



The surface is nearly smooth ; the longitudinal ribs, or rather lines, scarcely affecting 

 the evenness of the surface ; it is the most slender example of the genus w.hich the Great 

 Oolite has produced. Length, 3 lines. 



Locality. Ancliff; and very rarely Minchinhampton Common, in the planking. 



Rissoina cancellata. Plate IX, figs. 12, Via. 



R. Testa turbinatd, turritd, acuta; anfractibus convexis (8), angustis, transverse costatis; 

 costis (6 — 7) inmqualibus, lineis longitudinalibus decussatis ; aperturd lata. 



Shell turreted, turbinated, acute ; whorls convex (8), narrow, transversely costated ; 

 costae (6 — 7) unequal, decussated by longitudinal lines ; aperture wide. 



The upper costse of each whorl are smaller and more approximated than the lower ; the 

 convexity of the whorls is chiefly upon their lower portions ; the fine longitudinal lines 

 crossing the narrow encircling costse give to the surface a cancellated aspect ; the aperture 

 is acute above, rounded beneath. 



Locality. The soft Oolite beneath the planking of Minchinhampton Common furnished 

 this pretty little shell, of which we have not seen another example. 



Rissoina tricarinata. Plate IX, fig. 13. 



R. Testa parvd, turbinatd, acuta; anfractibus convexis; tricarinatis ; carinis crenulatis; 

 carina superiore apud suturam positd; aliis in medio et approximatis ; anfractu ultimo ad 

 basem lineis tenuissimis notato; aperturd parvd, suborbiculari. 



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