Two new species of Cymbella (Bacillariophyceae) from China, with comments on their valve dimensions

Abstract

Two new species of Cymbella, Cymbella stigmacentralis sp. nov. and C. compactiformis sp. nov., are described. Both C. stigmacentralis and C. compactiformis have a wide size range, with distinctive valve outlines that change markedly from the largest to the smallest. They also occasionally show one or two stigmoid-like pores on their dorsal (secondary) side. Cymbella stigmacentralis and C. compactiformis share features of the apical pore field: a complete area which is not divided by the distal raphe fissure; round foramina arranged in parallel; each pervalvar row of foramina covered internally by an undulate flap-like silica strip. Based on the characteristics of these two new species that lack a constant valve outline, and their fine morphological structures, it is worth studying species of Cymbella more intensively.