EVIDENCE FOR CHEMICAL BORING IN PETRICOLA LAPICIDA (GMELIN, 1791) (BIVALVIA: PETRICOLIDAE)

Specimens of the dead coral-boring bivalve Petri-cola lapicidahave been obtained from Thailand and Jamaica. Although formerlyconcluded to be a mechanical borer, examination of the burrowand the shell strongly suggests chemical boring. Two glandslocated in the inner mantle folds around the antero-ventr'alpedal gape are thought to be involved in this, although onemay secrete the calcareous material cemented to the posteriorshell margin Less specialised petricolids are mechanical borers of stiffmuds, shales and calcareous rocks. A few are nestlers, e.g.,Claudiconcha. As has been recently suggested for other familiesof borers, the Petricolidae constitute another example of theevolution of a specialised chemical borer from a less specialisedmechanically-boring ancestor (Received 20 July 1987;