Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe Author Prokina, Kristina I. Author Zagumyonnyi, Dmitry G. Author Tikhonenkov, Denis V. text Acta Protozoologica 2018 57 4 243 266 http://dx.doi.org/10.4467/16890027ap.18.018.10094 journal article 10.4467/16890027AP.18.018.10094 1689-0027 12637411 Acanthocystis costata Zlatogursky, 2015 ( Fig. 2F–I ) Description: Straight or slightly curved spine scales consist of a hollow shaft and circular base. Shaft is 5.0– 10.78 µm in length and 0.29–0.34 µm in diameter, base is 0.96–1.21 µm in diameter. Tip of shaft divided on 4–6 furcae (0.43–0.65 µm in length). Oval plate scales are 3.18–3.78×1.59–2.15 µm, with concave lateral sides, medial thickening (0.55–0.72 µm in length) and dense margins. Some plate scales have numerous small granules ( Fig. 2I ), others are ornamented with about 50 short (0.15–0.27 µm) radial slits ( Fig. 1H ). Remarks: This species was previously noted only once from the freshwater pool in the greenhouse of the botanical garden of St. Petersburg State University, St. Petersburg , Russia ( Zlatogursky 2015 ). Morphology of observed scales completely corresponds with the original description.