68 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



Common, collected by E. Witchell, Esq. A specimen has also been brought under my 

 notice by S. P. Woodward, Esq., but its locality is uncertain. 



TANCREDIA GIBBOSA, Lye. Tab. XXXV, fig. 7. Tab. XXXVI, fig. 1 1. 



TANCREDA GIBBOSA, Lye. Cott. Hills Handb., p. 121, pi. 7, fig. 4. 



Testa subtrigona, tumidula, umbonibus mcdianis acutis, latere antico attenuate, postice 

 tumido subangulate ; dorso l&vigato, plicis increments, paucis irregularibus. 



Shell subtrigonal, tumid; umbones elevated, pointed, and placed a little anterior to the 

 middle of the valves ; the anterior side is rather attenuated and pointed at the lower 

 extremity ; the posterior side slopes obliquely downwards, it is somewhat tumid, and has an 

 oblique angle slightly defined ; the surface is smooth, but with a few plications of growth 

 towards the lower border. 



Height, 10 lines; length, 13 lines; diameter through both the valves, 6 lines. 



It is distinguished from other Great Oolite species by the combination of a trigonal 

 outline with a tumid figure. 



Geological Position and Locality. It occurs rarely in the Great Oolite shelly 

 weatherstones of Minchinhampton Common, and the Forest Marble of Farleigh, 

 Somerset. 



TANCREDIA MACTR^OIDES, Whiteaves, MSS. Tab. XXXV, fig. 4. 



Testa ovato trigona, convexa, umbonibus submedianis elcvatis, incurvis ; margine antico 

 breviore, leeviter excavato, margine postico oblique declivi, angulo oblique leeviter instructe, 

 basi elliptico curvato. 



Shell ovately trigonal, convex, with a few concentric plications ; umbones antero- 

 mesial, elevated, and incurved; anterior border the shorter, slightly concave; the extremity 

 pointed ; posterior hinge-border sloping obliquely ; there is also a posterior oblique angle 

 faintly marked. 



lancredia gibbosa, Lye., approximates to this species, but is more convex, with a more 

 elevated and rounded posterior slope. T. axiniformis, Phil., from the Inferior Oolite of 

 Yorkshire, is more flattened, with more pointed umbones and acute posterior angle. 

 Height two thirds of the length. 



Geological Position and Locality. The Great Oolite of Stonesfield, Oxon., where it 

 appears to be rare ; collected by J. F. Whiteaves, Esq. 



TANCREDIA SIMILIS, Whiteaves, MSS. Tab. XXXV, fig. 9. 



Testa ovato clongata, umbonibus antcmedianis, latere antico attenuate, breviore ; postico 

 convexo, angulo obtuso obliquo j basi ettiptica curvata. 



