REVISION OF THE SPECIES COMPOSITION OF TH E GENUS CHOANOCYSTIS (SARCODINA, CENTROHELIOZOA) AND ITS FAUNA IN EASTERN-EUROPE

The species composition of the genus Choanocystis is discussed. Only m orphological features of the elements forming periplast are suggested to be used as taxonomic characters for this genus. These are: the shap e of the apices of spicules and the presence of marginal teeth, the sh ape of the edges of basal plates, the shape of spicular shafts, the sh ape and ornamentation of lamellate scales. Basing on these characters C. cordiformis is considered as a synonym of C. pantopoda, C. cordifor mis ssp. parvula - as a synonym of C. perpusilla; C. granulata and C. pertusa - as synonyms of C. rhytidos; C. rotundata ssp. rotoairense - as a good species C. rotoairense. A study of the fauna of Choanocystis spp. of Eastern Europe is carried out. C. aculeata, C. pantopoda, C. rotoairense and C. lepidula ssp. rossica were found in freshwaters, C. pelagica and C. kareliensis - in the White Sea, C. rotoairense - in t he Black Sea. A new subspecies C. lepidula rossica ssp. n. reported fr om the Moscow district, the delta of the Volga and Estonia is describe d. It is characterized by tapering shafts of spicules, the absence of marginal teeth, straight edges of basal plates and patternless lamella te scales.