32 MOLLUSCA FROM THE GREAT OOLITE. 



PINNA CUNEATA, Phillips. Tab. VI, fig. 11. 



PINNA CUNEATA, Phillips. Geol. Yorksh. i, t. 9, f. 17, 1835. 



Testa elongatd, subcurvatd, quadriquetrd, latere antico convexo, postim compresso, 

 margine acuto et excavato ; superficie lineis undulatis radiantibm subnodosis aliis concen- 

 tricis decussatis. 



Shell elongated, somewhat curved, four sided, anterior portion convex, its margin 

 convex, posterior portion compressed, its margin acute and excavated ; the entire surface 

 with undulating knotted radiating lines crossed by others concentrically disposed. 



The concentric lines are very irregularly disposed, being much more closely arranged 

 and indistinctly marked as the shell increased in size, at first they are not more numerous 

 than the radiating lines. Length about 3J inches, basal diameter 2J inches, diameter 

 through both the valves, 13 lines. In Gloucestershire, it occurs only in the upper division 

 of the Inferior Oolite. 



Localities. In the slaty Oolite of Easton and Collyweston, Northamptonshire, and in 

 Lincolnshire ; in the Cave Oolite of Yorkshire. 



TRICHITES, Lhwyd, 1699. 



TEICHITES, Plot, 1676; Lhwyd, 1699; Guettard, 1750; Defrance, 1828; 



Pietet, 1845; Lycett, 1850; Deahayes, 1851. 

 TESTA INCEKTI GENEKIS, Woodward, 1723. 

 PINNIGENE, Deluc, 1799. 

 CATILLUS, Sp., Pusch, 1836. 

 PINNA, Sp., Deshayes, 1835. 

 PlNNIGENA, D'Orbigny, 1851. 



Gen. Char. Shell of fibrous structure, thick, inequivalve, inequilateral, subquadrate, 

 the valves anteriorly forming a prominent and somewhat pointed apex curved obliquely 

 forwards. The left or larger valve convex and very thick, its apicial extremity hollowed 

 internally, and forming with the corresponding portion of the other valve a funnel-like 

 cavity, which is more or less open at its extremity; the right valve is thinner and 

 flattened, or sometimes somewhat concave ; the margins of the valves are very irregular 

 and sinuated, but fit closely together all round, and there is always a large flexure upon 

 the posterior side of the shell, forming a wide depression in that portion of the larger 

 valve and a corresponding elevation in the smaller valve. The hinge border is very 

 irregular and sinuated, it is nearly horizontal, lengthened, and internally without teeth, or 

 any testaceous thickening. The interior side of the larger valve is much thicker than the 

 other, its border is excavated beneath the apex, and is somewhat corrugated. The 

 muscular impression is single, large, subcentral, and strongly impressed, its circumference 

 has concentric step-like ridges. Ligament probably linear and subinternal, as in Pinna. 



The individuals of a species vary much in the convexity of the valves and in the 



