Lagenodifflugia sphaeroideus (Tarnogradsky, 1961) Chardez, 1990

Diagnosis: Shell pyriform, circular in cross-section, anterior part prolonged into a well marked neck; test entirely formed of angular mineral particles welded by an organic cement. Base of the neck surrounded by larger quartz fragments. These elements form inwards a constriction acting as a diaphragm. In apical view, these large elements provide an irregular opening which is more or less circular and more or less central, rather small, thus separating the test into two distinct parts, the more or less oval posterior part and the collar ending in the circular pseudostome (Chardez, 1990).

Dimensions: Tarnogradsky (1961): shell length 99 µm, width 60 µm, anterior margin 38 µm, width of throat or neck at base 48 µm. Chardez (1990): length 99-112 µm, width 50-60 µm, height of the neck 33-35 µm, diam. of aperture 18-30 µm (n=14).

Habitat: Fresh water, sphagnum, Caucasus, Rumania, Tirol.

Remarks: Tarnogradsky (1961) gives a very short description in Russian, translated: “Characteristic for this species is the blackish color of the posterior round or wide-oval part of the test and a transparent, narrowing neck.”

Probably, this species is a synonym of L. bryophila (Penard, 1902).