[6g]

Carina (fig. 4a). In Mr Tennant’s collection there is a carina from the chalk of Kent, different from any other seen by me, and which, from being plainly ridged, or rather furrowed longitudinally, I provisionally describe here. Valve thin, triangular, moderately tapering; very slightly bowed inwards; transversely, very flatly arched; plainly sub-carinated; lateral edges narrowly and much inflected; basal margin rectangularly pointed. A very small portion of the valve projected freely. The internal concavity of the valve is angular, instead of, as usual, being rounded. The whole exterior surface, except close on each side of the central ridge, is longitudinally furrowed.