Choanocystis granulata (Dürrschmidt, 1987) Siemensma, 1991
Syn.: Acanthocystis granulata Dürrschmidt, 1987
Diagnosis: Periplast, 35-40 µm in diameter (measurement based on whole mount), with two types of scales; details of protoplast unknown. Spine scales, 10-13 µm long, bipartite, consisting of shaft and base-plate. Shaft, 0.19 µm thick, cylindrical, slightly tapering. Distal end with 4 tiny marginal teeth. Shaft seated eccentrically on a heartshaped base-plate, sometimes with slightly irregular outline. Periphery with a narrow rim. Ornamentation consists of an axial thickening, surrounded by a distinct pattern of radial slits, each ca. 0.27 µm long and up to 0.03 µm wide, located about midway between median thickening and rim of the scale. Small granules are scattered all over the surface, sometimes regularly arranged in radial rows.
Remarks: C. granulata is easily distinguished from closely related C. pertusa by the presence of numerous granules on the plate scales, the less distinctly developed radial slits, which are located midway between the median thickening and the marginal rim. In C. pertusa these are close to the median thickening. C. granulata has so far only been observed in samples from the Banado Cruces.