Descriptions of two new marine scuticociliates, Pleuronema sinica n. sp. and P. wilberti n. sp. (Ciliophora: Scuticociliatida), from the Yellow Sea, China.

Two new marine scuticociliates, Pleuronema sinica n. sp. and P. wilberti n. sp., collected from the sand beach of Qingdao, China, were investigated in vivo and following protargol impregnation. Ciliates of the genus Pleuronema are normally recognizable by their large sail-like paroral membrane although one species, P. grolierei, has shorter cilia in the paroral membrane. Neither of the new forms has the conspicuous paroral membrane in vivo so in this respect they are not typical members of this genus. Pleuronema sinica is characterized by its large, conspicuously flattened body, the possession of only one preoral kinety, the irregular-shaped macronucleus and the rather unusual structure of the oral apparatus. By contrast P. wilberti has a medium-size broad-oval body, six to eight preoral kineties and a highly differentiated membranelle 3 that is five- or six-rowed. An identification key is supplied for the 15 species of Pleuronema for which the infraciliature is known.