V.—Note On a Bed of Red Chalk in the Lower Chalk of Suffolk

^{page 24 note 1} Since this paper was read, additional evidence that diamonds originate by the action of peridotites on carbonaceous rocks has been collected from many localities. The most instructive examples are from New South Wales, where the diamond gravels lie near the contact of basalts or serpentine with Carboniferous rocks, the serpentine here being an altered olivine enstatite rock. At the Bingera diamond-field a mass of eruptive serpentine is almost surrounded by Carboniferous rocks containing coal-seams.inWestern America, also, the diamantiferous gravels are near higher ground, where serpentines and carbonaceous rocks occur together. Possibly a clue may be thus afforded for more systematic search.