An analysis of the growth bands and ridges of barnacle shell plates

Periodic structures indicating discontinuous growth of shell wall plates have been observed in thin sections of shell and on the outer surface of shell plates of many species of operculate (Bourget, 1975). When sectioned and etched the shell plates appear to be composed of successive thin layers of shell material, each layer consisting of a few rows of fine crystals. Where two layers are adjoined, a dark line, marking the junction of two incremental zones, is clearly visible. The thin layers of shell have been termed growth bands whereas the junction of adjoining layers will be referred to as the growth line.