Müller, 1773
Body ellipsoid to barrel-shaped, starving specimens fusiform; anterior end nonciliferous, narrowed and set off forming frontal plate. Sometimes slightly flattened laterally. One spherical macronucleus; disintegrated to 2-4 globules in a terrestrial population. Micronucleus in indentation of macronucleus. Contractile vacuole invariably in posterior end of body. Resting extrusomes rod-shaped and indistinct. Somatic kineties 9-11, usually 10, in number with paired basal bodies in anterior half. One long caudal cilium distinctly bent distally. Oral apparatus half as long as body, composed of 3 small adoral membranelles and 1 paroral membrane with long cilia (spread sail-like in resting specimens). Movement jumping and gliding, rests with cilia rigidly spread. Size in vivo 14-30 x 6-16 µm. There are several rather similar Cyclidium spp., which need reinvestigation with modern silver impregnation.
Ref.: Didier and Wilbert (1981), Song and Wilbert (1989), Foissner et al. (1994), Foissner (1996).