Species: 45-100 μm long, 30-70 μm wide; short posterior prolongation
slightly curved; a prominent ridge on the convex side; longitudinally striated;
one ? circular paramylon (paramylum) body near center; flagellum as long as cell body (Kudo, 1966).
Cell body nearly spherical at dorsal view; anterior end separated into two spherical projections;
cauda strongly curved; dorsal ridge short or absent
(cf. dorsal ridge present P. triqueter);
cell body 40-80 μm long, 30-50 μm wide;
two ? paramylon bodies disc-shaped; striae straight
(An Illustrated Guide to Freshwater Zooplankton in Japan, 2000).