90 MOLLUSCA PROM THE GREAT OOLITE. 



Shell small, smooth, nearly orbicular, rather depressed ; umbones mesial and small ; 

 lunule ovate ; area lanceolate. 



The nucleus figured by Goldfuss from the Coral Rag of Nattheim, agrees in form with 

 our little species, and they are probably identical. 



Height, 5^ lines ; lateral diameter, 7 lines. 



Localities. Bisley Common, at Eastcombs, and Bussage. 



Cyprina depressiusctjla. Tab. XIII, fig. 4. 



Testa suborbiculari, lavi, convexo-pland ; umbonibus medianis parvis aculis • lunula 

 subexcavatd ; margine postico curvato ; basi arcuatd. 



Shell suborbicular, smooth, and slightly convex; umbones mesial, small, and 

 pointed ; lunule slightly excavated ; hinge margin curved ; base regularly rounded. 



The smooth, rather depressed surface, the mesial pointed umbones, and absence of all 

 angularity in the outline, are the leading characters of this shell, which appears to be rare. 

 Its position is the soft shelly Oolite, about the middle of the shelly beds. 



Height, 8 lines ; lateral diameter, 9| lines. 



Locality. Minchinhampton Common. 



Cyprina nuciformis, Lycett. Tab. XII, fig. 4. 



Cyprina nuciformis, Lycett. Journ. Geol. Soc, 1853, vol. 9, p. 340, pi. 14, fig. 3. 



Testa subnuciformi, convexd ; umbonibus magnis curvatis ; marginibus rotundis ; latere 

 postico angulo obtuso obliquo ; lunula excavatd. 



Shell subcordiform or nut-shaped, convex; umbones large, prominent, and curved 

 forwards ; margins of the valves rounded ; posterior side with an oblique, obtuse angle ; 

 lunule large, slightly excavated. 



A very convex species, with large umbones, less oblique and more convex than Venus 

 trapeziformis, Roemer. 



Height and length equal; convexity of the valves one third less. 



Localities and position. In Gloucestershire it occurs in the middle portion of the 

 Inferior Oolite ; our specimens are from the Great Oolite of Ponton, in Lincolnshire. 



Genus — Tatntcredia. Lycett, 1850. 



Tancredia, Lycett. Ann. Nat. Hist., 1850, p. 407. 



Hettangia, Terquem, 1852. Buvignier. Statistique Geologique, Mineralogique et 

 Pale'ontologique du Departement de la Meuse ; Atlas, p. 14. 

 — Terquem, Bull. Soc. Geol. de France, 10. p. 368. 



Gen. Char. Shell equivalve, subaequilateral, smooth, somewhat flattened, transverse, 

 donaciform ; umbones nearly mesial, small, contiguous, flattened ; anterior extremity 

 usually pointed ; no lunule ; posterior side more convex, with an oblique angle more or 

 less conspicuous, the extremity truncated, and more or less gaping; ligament short, 

 externa], placed in a small depression; basal margin lengthened, curved, or elliptical j 



