Amongst the specimens sent many years ago, from South Africa, by the late Mr. Andrew Geddes Bain, to the Geological Society of London, are two small blocks of greenish-grey hard mudstone or shale, very slightly calcareons; one bed-plane in each, specimen bears upon its surface numerous valves of one or more forms of small Lamellibranchs, closely resembling the shells of the genera Cyrena and Cyclas in contour.