Definitions

apical portion of either valve or bivalved crustaceans (e.g., Conchostracan, Phyllocarida); in cirripeds, central point on plate from which successive growth increments extend. [Moore and McCormick, 1969]
Apical portion of either valve or bivalved crustaceans; also location on plate from which successive growth increments extend in lepadomorph Cirripedia. [McLaughlin, 1980]
(Taxon-specific: Order Diplostraca) Somewhat elevated, dorsalmost part of carapace; represents early growth stage of shell. Position relative to anterior end is of taxonomic importance. [Stachowitsch, 1992]
(Taxon-specific: Subclass Cirripedia) Barnacle plate feature: in stalked barnacle, location on plate form which successive growth increments extend. (basal, subapical, subcentral). [Stachowitsch, 1992]