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).
 
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Phacus curvicauda Swirenko: Cell body 24-26 μm diam., (25)-38-30 μm long; 2 paramylons (Illustrations of The Japanese Fresh-water Algae, 1977).