The structure of the ctenidium of the Pen shell Atrina (Servatrina) lischkeana was examined. The pen shell provided the structures which were not observed to other bivalve: The ciliated canal of the mantle through which debris was passed out from the mantle chamber, and the mantle gland in the supra-branchial cavity. The gill type showed the heterorhabdic pseudolamellibranch: principal filaments and ordinary filaments were joined by inter-filament connecting membrane, and principal filaments of inner and outer laminae by the inter-laminar connecting bars.
Pen shell
ciliated canal of the mantle
heterorhabdic pseudolamellibranch
inter-filament connecting membrane
inter-laminar connecting bar
mantle gland