Cells solitary, motile, dorsoventrally compressed, not metabolic, of variable shape, often oval, obovate, ovate or pyriform, often slightly asymmetric in dorsal view, (5|-)6-9(-13) X x p.. Two unequal, heterodynamic flagella and a contractile filament arising ventrally, close together, g-g of the body length from the anterior end. The long flagellum thick (about 0,4 p.) convoluted, 14-17 \x long, covered with tiny cylindrical to clubshaped scales, the basal part with very delicate hairs. The short flagellum 3-4J p. long, about 0,2 p, thick. Contractile filament up to four times the length of the cellbody when fully extended, thickness variable, 0,1-0,2 p,, basal part thicker, 0,3 p., covered with very delicate hairs. The contractile filament displays in transverse section a cavity surrounding partially or complete about 8 fibres arranged in a ring. Chromatophores two, large, parietal and lateral, yellow-green, extended over ■§■ of the sides of the cell, oval. In each chromatophore a pyrenoid central on the inner side. Pyrenoids without apparent reserve material.