Representatives of the genus Phalansterium have single anterior flagellum surrounded by cytoplasmic collar. They belong to the class Variosea, which includes both typical amoeboid organisms (e.g., Flamella, Filamoeba) and some flagellates (e.g., Phalansterium, Multicilia). A recent study revealed Phalansterium arcticum as a very polymorphic species with both sedentary and swimming cells. It also clarified the mode of phagocytosis, and showed a cell division, but the ultrastructure of the cell is still not sufficient. Here, we present for the first time a thorough ultrastructural investigation of the soil flagellate Phalansterium “solitarium” strain Ph185 of SCCAP. We demonstrate that Phalansterium uses pseudopodia to take up bacteria inside its collar, and suggest that the inner cell asymmetry of Phalansterium cytoskeleton is associated with its mode of feeding. On the base of morphology and molecular phylogeny, we describe a new species Phalansterium foulumis with the type strain SCCAP-Ph185.