Abstract
The Stichaeid genus Dictyosoma has so far been regarded as represented by a single species, D.burgeri.Critical examination of specimens referred to Dictyosoma revealed that this genus includes two species.D.rubrimaculata is described as new.This species is distinguished from its congener, D.burgeri, by the lateral line structure, counts for dorsal and anal fin rays and vertebrae and coloration.It was also detected that there are two geographic forms in D.burgeri.D.rubrimaculata occurs along the Japanese coasts of the Pacific and theSea of Japan, and is sympatric in its range with both of the two forms of D.burgeri.In the Pacific coast the two species show more or less clear isolation in their habitat preference;D.rubrimaculata inhabits rocky and weedy shores, while D.burgeri commonly inhabits poorly vegetated, sandy to rocky intertidal zones.Ecological isolation is not yet investigated in the Sea of Japan.Morphological and ecological observations suggest that D.rubrimaculata is more primitive than D.burgeri.
