Abstract
The Japanese form of Daphnia obtusa Kurz, 1874 emend. Scourfield, 1942 is described. This taxon was recorded as a variety of D. pulex (De Geer) in Japan by UÉNO (1927), but has not been definitely described in the Japanese literature since SCOURFIELD's revision (1942). In Toyama Prefecture, D. obtusa occurs only in Yadoya-ike Pond, a small-shallow and turbid pond, from early March to early May.
