Choanocystis pantopoda (Penard, 1904) emend. Dürrschmidt, 1987
Syn.: Acanthocystis pantopoda Penard, 1904
Diagnosis: Periplast, ca. 60-70 µm in diameter, with two kinds of scales. Spine scales straight or slightly curved, 25-30 µm long, tapering slightly to a blunt apex with a toothed margin of 6 triangular teeth. Shaft, cylindrical and hollow, the sides are of irregular thickness (ca. 0.5 µm thick), basal sometimes with siliceous nodules. Base of the spine seated eccentrically on a heart-shaped base-plate, 1.5 µm in diameter. Plate scales patternless, elongated elliptical with a distinct median constriction, 3.5-4.0 x 2.3-2.5 µm.
Remarks: This species is easily recognized, with light- and electron microscopy, by the shape and size of the periplast and the extremely long, strongly built, spine scales, 1.5-2 times the cell diameter in length. C. pantopoda is distinguished from C. cordiformis on the basis of the length and breadth of the spine scales and the appearance of the plate scales, which are thicker than those of C. cordiformis.