Acanthocystis takahashii Dürrschmidt, 1987
Diagnosis: Periplast, 20-30 µm in diameter (measurement based on whole mount) with two types of scales. Plate scales, 2.5-3.2 X 1.5-1.8 µm, elliptical or pear-shaped, patternless except for a narrow marginal rim and an axial thickening. Spine scales, 2.5-10 µm long, tripartite, consisting of base-plate, shaft and trifurcate apex. Shaft, 0.19 µm thick, cylindrical and hollow, attached to a circular base-plate, 0.5 to 0.8 µm in diameter, surrounded by a narrow marginal rim. Apex separated into 3 diverging arms interconnected by a flaring of the distal portion of the spine shaft. Arms tapering, distal edges with 1-4 small teeth. Spine scales apically closed.
Ecology: Distribution: Japan, Sri Lanka, Canada, USA.
Remarks: The appearance of A. takahashii is reminiscent of A. cornuta, but a confusion of the two is ruled out by the shape of the spine scale apices: trifurcate in A. takahashii, bifurcate in A. cornuta. In all other aspects the species are similar.