The morphology and biostratigraphy ofTabellaria quadriseptata(Bacillariophyceae) in acid waters and lake sediments in Galloway, Southwest Scotland

Abstract
Details of valve morphology are used to differentiate between Tabellaria quadriseptata Knudson and T. flocculosa (Roth) Kütz. in cleaned material. Results substantiate Knudson's species description of T. quadriseptata. Characteristics used to separate the two species are valve shape, nature of marginal spines, and location of the labiate process. The palaeoecological value of splitting T. quadriseptata from the T. flocculosa complex is demonstrated by their comparative biostratigraphy in 210Pb dated sediment cores from three acidified lakes in Galloway.