Family: Cyrtos in rear 1/2 of body, hidden by ventral pellicular fold.
Genus: Cytostome just behind equator, in 3rd quarter of body (Illustrated Guide, 1985). Ovoid or crescent, usually both anterior and posterior pointed; somewhat flattened with a ridged, ribbed armour; somatic cilature reduced; cytostome in a depression on the left side at the centre of the body; fibrous trichocysts (Carey, 1992).
Species: Cell body 35 μm long (Kahl, 1930).
D. obtusa Penard, 1922: Crescent or reniform; 30-35 μm long; ciliation reduced but individual cilia are long; anterior pointed; posterior rounded; large trichocysts; a contractile vacuole with an accesory vacuole; a single spherical macronucleus near cytostome (Carey, 1992).