Difflugia balcanica Ogden and Zivkovich, 1983
= D. biconcava Ertl, 1965 ?
Diagnosis: Shell ovoid or pyriform, with an aboral rounded cone or spine and laterally compressed; shell in lateral view with typical biconcave shape; aperture circular; shell composed of a mixture of small to large pieces of mainly flattish quartz, arranged to give a relatively smooth surface.
Dimensions: Ogden and Zivkovich: 100-143 µm long, 66-96 µm broad, aperture 29-32 µm. My measurements: 78-104 µm.
Ecology: I found this species in sediment of a ditch near Montfoort, the Netherlands.
Remarks: D. biconcava Ertl, 1965 is a very similar, but larger species. Ertl: 100-143 µm long, 66-96 µm broad, aperture 29-32 µm. My measurements: Naardermeer 149-190 µm (n=8); nucleus 31-39 µm; (n=2). Probably both species are identical or part of a species complex.