BIVALVIA, ey 
GERVILLIA ToRTUOSA, Sow., sp. var. Tab. XL, fig. 25. 
GASTROCHENA TORTUOSA, Sow. Min. Con., t. 526, fig. 1. 
= — Phil. Geol. York., t. 11, fig. 36. 
GeRVILLIA ToRTUOSA, Mor. Catal. Brit. Foss., 1854, p. 168. 
— a Oppel. Juraformation, p. 418. 
Testa elongata, antice tortuosa, postice recto, attenuato, umboni perobliquo, subter- 
minali; linea cardinis obliquissimo ; margine antico undulato, plicis concentricis leviter 
instructis. Valva dextra subconcava, tortuosa ; facies interna rgnota. 
Shell elongated, convex, and contorted anteriorly, straight and attenuated posteriorly ; 
umbo very oblique, with a small anterior auricle; hinge-border very oblique, anterior 
border undulated; the surface of the valve has five irregular, concentric plications upon 
its anterior side. The right valve is twisted conformably with the left valve; it is some- 
what concave, ‘The cardinal ligamentary pits have not been exposed in the present variety. 
Compared with the Inferior Oolite forms of Gervillia tortuosa, this variety is more 
narrow and less contorted, having the posterior extremity nearly straight; the umbo is 
also more acute, and the surface is destitute of the large, rugose, concentric plications 
which are conspicuous upon well-preserved examples of the typical form. So much 
variability, however, is seen in the contorted species of Gervillia that I prefer to regard 
the present as pertaining to G. fortwosa, but constituting a well-marked variety. 
Geological Position and Locality. It occurs rarely in the Cornbrash of Scarborough ; 
from the coHection of Mr, Leckenby. 
Gervituia Isuipensis, Lye. ‘Tab. XL, fig. 35. 
Testa, valva sinistra crassa, obliqua, convexa, linea cardinis elongata, auricula postica 
permagna, falerformi, dorso angulo obtuso obliquo instructo ; plicis incrementi paucis. Valva 
altera et foveolis internt rgnotis. 
Shell with the left valve thick, inflated, very oblique, with a lengthened hinge-line and 
falciform posterior auricle; the anterior border is slightly excavated, and there is an 
obtuse, oblique angle, which extends from the umbo to the posterior extremity of the 
valve, which is curved backwards; the folds of growth are few and prominent; the 
surface is destitute of ornament. The other valve is not known, nor has the hinge been 
exposed. 
The general figure much resembles that of @. crassicosta, Mor. and Lye., but it is 
more inflated; it has a greater posterior curvature, and is destitute of the oblique coste. 
The length of our largest example is 2 inches, that of the hinge-line 14 inch. 
Geological Position and Locality. The Cornbrash of Islip, Oxon., also the Great 
Oolite of Stonesfield ; collected by Mr. Whiteaves. 
