Cement and Iron in the Arenaceous Foraminifera

Abstract

The organic cement secreted by the twelve species of arenaceous foraminifera examined is considered to be a mucosubstance containing acid mucopolysaccharide to which iron, and probably calcium, is organically bound. A phase of mineralisation of the organic cement by calcium and/or iron salts, possibly also secreted by the animal, will produce a hard shell, whereas soft shells may have little, if any, mineral deposit. No significant difference has been found in the amino acid content of the cement obtained from forms representing four genera. Previously published analyses of the inorganic composition of arenaceous shells are examined. It appears that the high values for iron may have concealed relatively large amounts of aluminium and that the shells of arenaceous foraminifera may be much less ferruginous than is generally recognised. The colour of a shell is not a reliable guide to its ferruginous nature, since pure white and red-brown shells may be equally ferruginous. Cement and iron in the arenaceous foraminifera