Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre 1984) from Vietnam

The morphology of the inorganic scales of ten species of centrohelid heliozoans collected from various types of aquatic habitats in Vietnam has been examined. All the species identified are new to Vietnam. The spine scales of Acanthocystis turfacea are distinguished by the characteristic conically pointed tips of furcae and longer furcae relative to the shaft length in long spine scales. Morphologically, the plate scales of Pterocystis tropica examined correspond to those of the subspecies P. tropica paucistriata ; the spine scales, to those of the subspecies P. tropica tropica . The examined plate scales of Raineriophrys erinaceoides undulata lack radial slits, unlike those indicated in the original description of this subspecies. Two new species of centrohelid heliozoans are described. Pterocystis vietnamica sp. n. is characterized by leaf-shaped spine scales with transverse slits on the lateral wings and a large, spherical, subapical protrusion. Pseudoraphidocystis dentata sp. n. has marginal teeth at the edges of funnel-shaped spine scales.