BIVALVIA. 59 
upon the posterior side, which deeply indent the shell, and are therefore always 
conspicuous. The Cardium cognatum of Goldfuss is a very different shell, having a 
posterior angle and oblique umbones. D’Orbigny (‘ Prodrome’) has arranged our species 
with his genus Unicardium, in which he has been followed by Dr. Oppel (‘ Juraformation’) ; 
but, having examined the muscular impressions and also those of the hinge, I can affirm 
that Professor Phillips correctly discriminated the genus. 
Geological Positions and Localities. The specimens figured are from the Cornbrash 
of Scarborough ; it occurs also in the Kelloway Rock of the same neighbourhood and in 
Wiltshire. 
Carpium Witcueni, Lyc. ‘Tab. XL, fig. 36. 
Testa parva ovato-trigona, convera, umbonibus magnis prominentibus medianis, sub- 
acutis, latere posteriore angulo obliquo et area postica planata, in medio sulco obliquo in- 
structo ; dorso striis tenuissimis concentricis regularibus. 
Shell small, ovately trigonal, convex; umbones mesial, prominent, and somewhat 
pointed ; the anterior and lower margins are rounded; the posterior margin is somewhat 
angulated at its lower extremity; the posterior side has a conspicuous, oblique angle, 
separating a flattened, smooth, posterior area, which is traversed by a mesial, oblique furrow ; 
the other portion of the surface has very fine, regular, concentric striations. The height 
and length are equal ; the diameter through both the valves is somewhat less. 
The abruptness of the posterior angle, the flattened, smooth area, with its mesial 
groove, appear to separate it from other allied Jurassic species. Possibly it may be a 
dwarfed representative of a much larger form. 
Geological Position and Locality. he Great Oolite of Bussage, near Bisley Common ; 
the process of crushing shelly portions of the white Oolite has yielded this little species 
to Mr. Witchell. 
Cypricarpia caupata, Lyc. ‘Tab. XXXVI, figs. 8, 8 a. 
Testa transversa, subtrigona, obliqua, subdepressa, umbonibus magnis, elevatis, sub- 
tnvolutis, incurvis, latere postico oblique declivi, obtusangulo instructo ; lunula depressa ; 
valvis stris longitudinalibus tenuissimis, inequalibus, latere antico semel striis radiantibus 
tenuissimis decussatis. Nucleo striis obscuris radiantibus et concentricis. 
Shell transverse, subtrigonal, oblique, rather depressed; umbones large, elevated, and 
subinvolute; the posterior side slopes obliquely downwards, and has a slightly defined, 
obtuse angle; the anterior side is moderately produced; the lunule is strongly defined ; 
