BIVALVIA. 71 
Geological Positions and Localities. The specimen figured was obtained by 
Mr. Whiteaves in the Great Oolite of Kirklington, Oxon. ; it has also occurred rarely in the 
same formation at Minchinhampton Common, and in the Cornbrash of Islip, Oxon. 
Cyprina BELLA, Lyc. Tab. XL, figs. 15, 15a. 
Testa ovato-orbiculari levigata, subdepressa, umbonibus mediocris, antero-medianis, 
margine cardinali recto, subhorizontali, postice subangulata, lunula angusta viv depressa ; 
superficie angulo postico obliquo instructo ; striis incrementi crebris, irregularibus. 
Shell transverse, ovately orbicular, smooth, rather depressed; umbones of moderate 
size, but little elevated, placed a little anterior to the middle of the valves and curved 
forwards ; hinge margin straight, nearly horizontal, and slightly angulated posteriorly ; the 
lunule is narrow, and but slightly impressed; the exterior surface has an oblique angle, 
posterior to which the surface is flattened ; the striations of growth, and delicate, numerous, 
and irregular. 
The depressed form, posterior subhorizontal straight hinge border, and oblique 
posterior angle, are the features that will serve to distinguish it from allied contemporaneous 
forms. The numerous specimens placed at my disposal include examples from two to 
nine lines in length, which measurements usually exceed the height by one fifth. 
Geological Position and Localities. The Forest Marble of Laycock and Pound Pill. 
In the collection of W. Walton, Esq. 
Cyprina Davinsont, Lyc. Tab. XXXVI, figs. 6, 6 a. 
Testa ovato-orbiculart crassa, convexa, obliqua, umbonibus obtusis submedianis antrorsum 
inflectis, marginibus arcuatis curvatis, latere postico area subplanata, angula obtuso obliquo 
interdum instructo, aut nullo ; lunula vie eacavata, inconspicua, superficie striis concentricis 
erregularibus. 
Shell ovately orbicular, thick, convex, oblique, but varying much in the length and 
obliquity ; umbones obtuse, submesial, directed forwards ; margins of the valves curved 
elliptically and close fitting, lunule not conspicuous and scarcely excavated ; the posterior 
side has a narrow, oblique, flattened space, sometimes separated from the other portion of 
the surface by an obtuse angle ; in other instances there is no distinct angle ; the surface 
has numerous irregular concentric and faintly marked plications. 
Dimensions of a large specimen of medium figure; length, 17 lines ; height, 15 lines ; 
diameter through the valves, 11 lines, 
It is liable to be mistaken for Cyprina Loweana, compared with which our shell is 
