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Genus Difflugia

Shell is agglutinated, with a terminal aperture that is circular, oval, lobed or toothed (but never slit-like), sometimes with a collar or necklace (sensu Ogden, Meisterfeld, 1989; Mazei, Warren, 2012, 2014, 2015) but never with an internal diaphragm. The shell is composed of mineral particles or diatom frustules, collectively called xenosomes that are assembled on structured or sheet-like organic cement. All species of Difflugia acquire their xenosomes from their environment. Many select and arrange these xenosomes according to their size and shape in order to construct a shell with a morphology that is unique to that particular species. The nucleus is usually ovular, but in some species it is vesicular. Several freshwater species have green endosymbionts (Meister- feld, Mitchell, 2008). Type species: Difflugia proteiformis Lamarc, 1816