AbstractSilén, L. (Department of Zoology, University of Stockholm, S‐113 86 Stockholm, Sweden) and Harmelin, J.‐G. Haplopoma sciaphilumsp.n., a cave‐lining bryozoan from the Skagerrak and the Mediterranean. Zool. Scr. 5 (2): 61–66, 1976.—Haplopoma sciaphilumsp.n. is described from submarine caves or cave‐like habitats at the west coast of Sweden and in the Marseille and Adriatic regions. Its morphological characters are very stable and identical within the wide area of distribution. Only the zooid size varies considerably, a variation apparently connected with temperature: the size decreases distinctly from the cold waters of the Skagerrak to the less cold Adriatic locality and even more to the warm localities of Provence. It is the only member of the genus known to be sexually dimorph, a phenomenon found as well in the genusCelle‐porellabelonging to the same family