Difflugia avellana  Penard, 1890

Diagnosis: The shell is relatively large, elongated ovoid, yellowish, and laterally compressed, with an oval cross-section, covered with flat mineral grains. The fundus gradually narrows towards the oval pseudostome. The cytoplasm does not completely fill the shell. The nucleus is spherical, and there is one contractile vacuole. Numerous long, cylindrical pseudopodia are present.

Dimensions: Penard (1890): Shell length 100–160 µm; width 60–130 µm; width 35–95 µm; pseudostome 28–48 µm. Specimens from a cave in Croatia were smaller, length 80 µm, width  47 µm.

Habitat: Freshwater. Sediment, Europe. The specimens from Croatia were collected in Jopićeva Cave by Najla Baković, 2023).