Pentagonia zhangduensis nov. spec. (Lobosea, Arcellinida), a new freshwater species from China.

The morphology of a new testate amoeba Pentagonia zhangduensis nov. spec. was investigated using light and scanning electron microscopy. The new species was discovered in the sediments of Lake Zhangdu, Hubei Province, China. The low coefficients of variation and normal size frequency distribution suggest that P. zhangduensis is a size-monomorphic species. P. zhangduensis differs from the one other species in this genus (P. maroccana), by its larger size and its quadrangular cross section with two parallel longitudinal ridges on each of the two flattened sides of the test.