Pyxidicula husvikensis (Beyens & Chardez, 1997) new comb.
Basionym: Microcorycia husvikensis Beyens & Chardez, 1997

Diagnosis: Upper test part dome‑shaped, with a yellowish tint. A very delicate punctation is visible at high magnification. The margin of the upper test part is divided into an external and an internal portion. The internal margin transitions into a flexible, hyaline membrane that spreads toward the periphery and forms a border around the upper test part. This membrane can fold upward toward the centre, reducing the diameter of the pseudostome. In young individuals the upper test part is hyaline and more pliable than in older ones.
The cell body forms a spherical or oval mass within the test and is connected to the upper test part by fine ectoplasmic epipodia, usually two or three in number. Pseudopodia are lobate. Cytoplasm finely granulate, containing numerous inclusions (excreta and glycogen granules) and a contractile vacuole. The cell is mononuclear; the nucleus contains a central nucleolus and measures 2.4–3.0 µm in diameter.
In lateral view the shell appears basin‑shaped, with a flattened or slightly bulged top, forming a short conical cylinder open at the base. The shell wall consists of a yellowish organic layer; at high magnification fine alveoli are visible. The shell membrane is composed of two agglutinated layers that separate near the base. One of these layers forms a thin, hyaline, extensible membrane that spreads circularly around the shell. This membrane may be extended like a sail or folded to reduce the basal opening.
Formalin‑fixed amoebae appear as a globular mass attached to the interior wall opposite the opening. The cytoplasm is finely granulated and grey, with a clearly visible spherical nucleus containing a central nucleolus.

Encystment: Two types of cysts occur.

• Resting cyst: Formed inside the test; completely spherical, 24 µm in diameter. Cytoplasm dense and opaque, surrounded by a smooth membrane.
• Pre‑encystment stage: Membrane rough and irregular, attached to a point on the test wall. Pre‑encysted cytoplasm approximately 28 µm in diameter. The lower test part folds toward the peristome centre, and the margin of the upper test part may also fold inward to reduce the test opening.

Type location: Husvik area. South Georgia (Sub-Antarctica).

Ecology: Slightly alkaline lakes and ponds vegetated by moss (Beyens & Chardez, 1997); moss (Chardez, 1999). Recorded from South Georgia, the Netherlands, and Austria (Siemensma, unpubl.).

Dimensions:

• Beyens & Chardez (1997): shell diameter 32–34 µm; shell height 16–18 µm; nuclear diameter 2–2.4 µm; diameter of contracted cytoplasm 18 µm; diameter of extended membrane 38–40 µm (n = 20).
• Chardez (1999): upper shell diameter 32–35 µm; height 16–20 µm; diameter including spread lower test part 39–43 µm.

Remarks: Microcorycia husvikensis clearly belongs to Pyxidicula. The species is therefore transferred from Microcorycia to Pyxidicula.