Campascus interstitialis  Golemansky, 1981

Diagnosis: Test elongated, in the shape of a bottle with a curved, colorless, transparent and very short neck. Fundus rounded, rarely ogival. Test in cross-section circular. Pseudostome round, rarely broadly oval, with a very delicate chitinous collar. Test is chitinoid and formed of a membrane embedded with idiosomes and rarely flat xenosomes, tight against each other. Sometimes they give the appearance of a fine cross-linking of the theca, similar to that of a Cyphoderia. Cytoplasm clear and hyaline, with a single nucleus. Filopodia, commonly 2-3, long and very fine.

Dimensions: Length of the test: 32-45 µm, width (diameter) of the theca: 15-23.5 µm. Pseudostome: 8-11 µm, collar: 9-15 µm.

Ecology: C. interstitialis lives in the underground waters of the sandy beaches of the Black Sea, Baltic Sea and the Atlantic. It is a euryhaline species observed in water salinity ranging from 3.4% – 22.85%.

Remarks: C. interstitialis differs from C. minutus Penard in its smaller size, its triangular cross section and especially its ecology. However, C. minutus lives in intercontinental lakes and its length varies from 50 to 60 µm (Penard 1902, 1908, Chardez 1965).