Ulnariashun-biseriata sp. nov. (Bacillariophyta) from the Shun River in Hunan Province, China.

A new species, Ulnariashun-biseriata sp. nov., was found in the Shun River of Hunan Province, southern China, and its morphology was described based on light and scannning electron microscope obervations. Ulnariashun-biseriata is characterized by its lanceolate valve outline, apiculate valve apices, slightly undulate valve margins, mostly biseriate striae, variable central area, and closed valvocopula. Many abnormal valves of U.shun-biseriata were observed in the samples investigated and the most frequent morphological abnormalities consisted of a lack of symmetry relative to the apical axis caused by a unilateral expansion in the middle part of the valve.