Order: No kinetidal specializations at oral region. Family: Free swimming; most body kineties bipolar, cytostome apical. Genus: Cytostome not preceded by invagination lined by body kineties. Species:

50 μm 100 μm 150 μm; x 400

H. sulcata Penard, 1922: Cell body cylindrical but short, 60 μm long, cytostome small, two or three long cilia present at peribuccal area, a single macronucleus central, contractile vacuole terminal, no trichocysts, longitudinal kineties crossed by fine transverse striations (Carey, 1992).