84 MOLLUSCA FROM THE GREAT OOLITE. 



ASTARTK ROTUNDA. Tab. IX, fig. 12. 



ASTAKTE ORBICULAEIS, Sow. Min. Con., t. 520, f. 2. 

 EOTUNDA, Morris. Catal. Brit. FOBS., p. 187. 



Testa crassd orbiculatd, convexd, umbonibus submedianis acutis, margine cardinali 

 obliquo, elongate, subrecto, lunuld magnd lanceolatd, plicis incrementi paucis, irregularibus ; 

 costis depressis, crebris et irregularibus. 



Shell thick, orbicular, convex ; umbones nearly mesial, prominent, acute ; hinge margin 

 oblique, lengthened, and nearly straight ; lunule large and lanceolate ; folds of growth few 

 and irregular ; costse depressed, small, closely arranged, and irregular. 



The general figure has a considerable degree of convexity ; the umbones are small, 

 pointed, and curved forwards, and are placed somewhat nearer to the anterior than 

 posterior side of the valves ; the extremity of the lengthened hinge border forms an angle 

 with the inferior margin. It is rare. 



Height nearly equal to the lateral diameter, which is 2 inches ; the diameter through 

 both the valves is \\ inch. 



Locality. Minchinhampton Common, in the planking. 



ASTARTE? RHOMBOIDALIS, Phil., sp. Tab. IX, fig. 20. 



ISOCAKDIA RHOMBOIDALIS, Phil. Geol. York., 1, t. 3, f. 28. 

 HIPPOPODIUM LUCIENSE, D'Orb. Prod. Paleont., p. 308. 

 BAJOCIENSE, D'Orb. Ib., p. 277. 



Testa crassd convexd, subquadratd, vel oblongd, umbonibus anticis obtusis, margine 

 cardinali elongato, subJiorizontali, hinuld magnd, excavatd, margine inferiore subrecto et 

 sinuato, marginibus internis integris, superjicie plicis incrementi paucis, magnis, distantibus ; 

 striis concentricis tenuissimis regularibus crebris. JEtate senili striis concentricis obsoletis, 

 plicis rugis magnis irregularibus. 



Shell thick, convex, subquadrate, or oblong ; umbones anterior, obtuse ; hinge margin 

 elongated, subhorizontal, but slightly arched ; lunule large, elliptical ; inferior margin 

 nearly straight, parallel to the superior border, and slightly sinuated ; internal margins of 

 the valves plain, acute ; folds of growth few, large, and distant ; concentric striations regular, 

 delicate, and closely arranged. In an advanced stage of growth the concentric striations 

 disappear, and the surface became rugose with the irregular plications of increase. An 

 oblique prominence or obscure angle extends downwards posteriorly, and becomes promi- 

 nent in specimens which are short and have the superior border much arched. The Great 

 Oolite examples are very numerous, and for the most part rather flattened arid rugose with 

 adherent shells, the largest specimens not unfrequently having been perforated or grooved 

 by the Lithophagidae ; the substance of the test is very thick, and the muscular im- 

 pressions are deeply excavated ; the cardinal teeth are remarkably large and massive. 



