Abstract
Japanese melithaeid type material is re-examined and re-described. The sclerites of the different species are depicted using Scanning Electron Microscopy. All Japanese species of the family Melithaeidae treated here belong to the genus Melithaea and are endemic to Japanese waters. Old museum material and newly collected specimens from Japanese waters are identified after comparison with this type material. Acabaria modesta var. abyssicola is regarded a separate species, here named Melithaea abyssicola (Kükenthal, 1909). In addition, 11 new species are described: Melithaea boninensis sp. n., Melithaea doederleini sp. n., Melithaea isonoi sp. n., Melithaea keramaensis sp. n., Melithaea oyeni sp. n., Melithaea ryukyukensis sp. n., Melithaea sagamiensis sp. n., Melithaea satsumaensis sp. n., Melithaea suensoni sp. n., Melithaea tanseii sp. n., and Melithaea tokaraensis sp. n.. Pleurocorallium confusum Moroff, 1902, Pleurocoralloides formosum Moroff, 1902, Melitodes flabellifera Kükenthal, 1908, and Melitodes densa Kükenthal, 1908 are synonymized with Melithaea japonica (Verrill, 1865). We have designated a neotype for Melithaea mutsu Minobe, 1929. A key to the Japanese melithaeids is presented.