The distribution of Artemiopsis stefanssoni is described. Samples from eight localities in Baffin Island and Somerset Island were analysed and showed wide variations between populations in body size and egg production. These variations probably correspond to variations in food availability. Maximum lengths recorded were 9.00 mm for males and 11.95 mm for females. The egg sac of this species has no genital opening. Successive clutches are retained within the egg sac instead of being released after fertilisation and deposition of the tertiary shell. Egg sacs contained up to 120 eggs, whereas maximum ovary output was 40 eggs per clutch. It is suggested that retention of eggs within the egg sac affords protection against egg predation by benthic feeders such as Branchinecta paludosa and Lepidurus arcticus.
