* P. bicarinata:
30-35 μm;
2 dorsal, 2 ventral grooves on either side of dorsal and ventral keels (How to know the protozoa, 1979).
P. mediocanellata:
21-26 μm;
with median, longitudinal grooves, dorsal and ventral (How to know the protozoa, 1979).
P. alata:
23-25 μm;
with one dorsal, one ventral, and two lateral grooves (How to know the protozoa, 1979).
P. asymmetrica:
18-25 μm;
pyriform, with a deep lateral groove (How to know the protozoa, 1979).