New marine gastrotrichs of the family Thaumastodermatidae (Gastrotricha: Macrodasyida) from Shirahama, Japan

摘要

Three new species belonging to the family Thaumastodermatidae are described on the basis of the specimens collected from the Pacific coast around the Seto Marine Biological Laboratory, Shirahama, Wakayama, Japan. Tetranchyroderma schizocirratum, new species, bears pestle organs, dorsal cu-ticular armature made up of tetrancres only, and three pairs of dorsolateral tubes, the last of which is shaped as cirrata with the distal part branched. Thaumastoderma clandestinum, new species, is clearly differentiated from its congeners by the character combination of six pairs of dorsal cirrata, a pair of simple spatulate tentacles, paired ventral adhesive tubes on the anterior region of the copulatory organ and accessory cirrata of last dorsal cirrata. Platydasys itoi, new species, is most allied to P. phacellatus Clausen in having the ven-trolateral cirri group in the form of tuft, but it is distinguished from the latter by the lack of lateral tubes and a different number of ventrolateral cirri and adhesive tubes.