Conchiolin Remnants in Mother-of-Pearl from Fossil Cephalopoda

Abstract

DECALCIFICATION of mother-of-pearl from recent molluscs leaves soft, stratified membranes of concholin. These membranes, cleaved and broken by ultrasonic vibrations, appear in the electron microscope as fragments of lace-like reticulated sheets or perforated leaflets¹. The pattern of these structures differs with the groups and species of molluscs. Three main patterns (nautiloid, gastropod and pelecypod) have been provisionally recognized¹. Replicas of surfaces of mother-of-pearl, prepared before and after corrosion by decalcifiers, have shown that the reticulated sheets correspond to the conchiolin membranes which alternate with the mineral lamellæ in the stratified nacreous configuration, and which separate the individual crystals of aragonite disposed side by side in each lamella².