84 MOLLUSCA FROM THE GREAT OOLITE. 



AsTARTE ROTUNDA. Tab. IX, fig. 12. 



Astarte orbicularis, Sow. Min. Con., t. 520, f. 2. 

 — rotunda, Morris. Catal. Brit. Foss., p. 187. 



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

 obliquo, elongato, subrecto, lunula magna lanceolatd, plicis incrementi paucis, irregularibus ; 

 costis depressis, crebris et irregularibus. 



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

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

 and irregular ; costae 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 2f inches ; the diameter through 

 both the valves is 1^ inch. 



Localiiy. Minchinhampton Common, in the planking. 



Astarte ? rhomboidalis, Phil., sp. Tab. IX, fig. 20. 



Isocardia rhomboidalis, Phil. Geol. York., 1, t. 3, f. 28. 

 Hippopodium Luciense, D' Orb. Prod. Paleont., p. 308. 

 — Bajociense, If Orb. lb., p. 277. 



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



cardinali elongato, subhorizontali, lunula magna, excavatd, margine inferiore subrecto et 



sinuato, marginibus internis integris, super jicie plicis incrementi paucis, magnis, distantibus ; 



striis concentricis tenuissimis regulariuus crebris. Jffiate senili striis concentricis obsoletis, 



plicis rvgis 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 and rugose with 

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

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

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



