ABSTRACT
In 1965, the brachiopod shell was described simply as impunctate, punctate or pseudopunctate. It can be shown that there are at least three types of pseudopunctae, and six kinds of punctae with only those of the terebratulides, thecideidines and spiriferides arising from the same stem group characterized by adistal microvillous brush. Yet five of these punctal types accommodated papillose outgrowths of the mantle serving as storage centres. The sixth kind, the canals of organophosphatic shells, could never have contained more than extensions of the secreting plasmalemma of the mantle. In Lingula at least, the canals support nets of actin, from which are suspended mosaics and botryoids of apatite in a gel of glycosaminoglycans. The shell of living Lingula is a complex sequence of laminae, disposed like lithostratigraphic members of a sedimentary basin with unconformities, oversteps and off laps and rapid facies changes from predominantly biomineralized to exclusively organic units.
