White-spot type (W-type) and black-spot type (B-type) of Pagurus lanuginosus De Haan were examined for their distribution in Japan, morphological differences in two characters, and a possibility of sexual isolation. W-type crabs were mainly found in areas directly subjected to oceanic water, whereas B-type crabs tended to inhabit rather protected areas. Morphological comparisons on accessory teeth of the 3rd maxilliped and molar teeth of the major cheliped revealed no consistent differences between the two types. Encounter tests composed of homotypic and heterotypic combinations suggested that the two types are sexually isolated. This suggested that they are different species, but detailed morphological comparisons on characters other than those treated in the present study are needed for specific discrimination.