 
 
|  Genus: Only 1 emergent flagellum; locomotory flagellum directed anteriorly, straight, during swimming; 
colourless, phagotrophic; no eyespot; rigid, solitary, ovoid, usually flat, with several keels; freshwater 
(Illustrated Guide, 1985).  
Oval or pyriform; not plastic; pellicle often with straight or spiral furrow; a single flagellum; many species 
(Kudo, 1966). Species: 30-35 μm; 2 dorsal, 2 ventral grooves on either side of dorsal and ventral keels (How to know the protozoa, 1979). 
 
 | 
 50 μm
 50 μm
 100 μm
 100 μm
 150 μm; x 400 :
 150 μm; x 400 : 
 31 μm
 31 μm
 63 μm
 63 μm
 94 μm; x 640
 94 μm; x 640
 
 
 
* 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).