Genus: Length often greater than breadth (Page, 1976).
Usually longer than broad (How to know the protozoa, 1979).
Body ovate in locomotion, broader than long; anterior zone not formed as superimposed waves
(Illustrated Guide, 1985). ???
P. placida: 15-35 μm long; clear anterior part about ssame length as granular posterior part; pseudopods only on radiate stage; nucleus with distinct endosome; fresh water (How to know the protozoa, 1979).