The structure of Melosira sulcata (Ehr.) Kütz. var. sulcata frustules from Lower Oligocene diatomites from Futoma (Carpathians, Poland)

Abstract

Budowa pancerzyków Melosira sulcata (Ehr.) Kütz. var. sulcata z dolnooligoceńskich diatomitów z Futomy (Polska) Under the light and scanning electron microscope the three known Melosira sulcata (Ehr.) Kütz. var. sulcata types of valve face ornamentation were observed; “f. radiata”, “f. radiolata”, “f. coronata”. Fourth type unknown so far, was found and described. It is characterized by the presence of a distinct swelling in .the centre of the valve face. Significant differences were noted between frustule structure of M. sulcata and the type species for Melosira genus — M. nummuloides C. Ag. The M. sulcata frustule is composed of a single (not 3, as M. nummuloides) layers of silica, has the labiate processes on the mantle (not on the valve face); and has no girdle bands. It is more like to the M. granulata (Ehr.) Ralfs and M . arenaria Moore groups, and it is suggested that occupy an intermediate taxonomic position between them.