Abstract
A new species of the euphausiid-ectoparasitic isopod in the genus Heterophryxus Sars, 1885 is described based on an immature female specimen collected from the central North Pacific. The new species, Heterophryxus pacificus, can be distinguished from the immature females of H. appendiculatus Sars, 1885 and H. elongatus Schultz, 1977 in having (1) a wider and thicker body, (2) a cephalon without an anterior hollow, and (3) complex-shaped pereomeres 2 to 4. A diagnosis of the genus Heterophryxus is provided.
