Genus Cryptodifflugia Penard, 1890
Diagnosis: Shell oval, egg-shaped, pyriform with a short neck, circular or oval cross-section, with adhering foreign particles or smooth surface, colorless, yellow or brown,
Genus Cryptodifflugia Penard, 1890
Diagnosis: Shell oval, egg-shaped, pyriform with a short neck, circular or oval cross-section, with adhering foreign particles or smooth surface, colorless, yellow or brown, composed of an outer proteinaceous material usually lined, aperture terminal, circular or oval. Pseudopods are in the form of ectoplasmic anastomosing reticulolobopodia.
Type species: Cryptodifflugia oviformis Penard, 1890.
Ecology: Fresh water, soil and mosses.
Key to the species
1. Shell distinctly compressed laterally → 2
– Shell not or only slightly compressed laterally → 7
2. Aperture oval → 3
– Aperture circular → C. compressa angustioris
3. Shell length 45–63 µm → C. angustastoma
– Shell length 32–45 µm → C. paludosa
– Shell length < 25 µm → 4
4. Shell width > shell length → C. compressa australis
– Shell width < shell length → 5
5. Shell lanceolate → C. lanceolata
– Shell pyriform → C. brevicolla
– Shell ovate → 6
6. Thick organic lip around the aperture → C. compressa
– No lip around the aperture → C. compressa ovata
7. Shell surface crenulate → 8
– Shell surface not crenulate → 10
8. Shell ovoid → 9
– Shell globose or subglobose → C. crenulata globosa
9. Shell length < 20 µm → C. crenulata
– Shell length > 23 µm → C. splendida
10. Shell pyriform with prominent neck; surface with rare sand grains → 11
– Shell ovoid or globular, without prominent neck → 13
11. Shell surface with rare sand grains → 12
– Shell surface smooth → C. collum
12. Shell length 16–26 µm; aperture 4–5 µm; neck ≈ 1/3 shell length → C. sacculus
– Shell length 27–30 µm; aperture 10–13 µm; neck ≈ 1/4 shell length → C. sacculus sakotschawi
13. Lateral sides conical (angular) → C. angulata
– Lateral sides rounded → 14
14. Aperture diameter equal to shell width → 15
– Aperture diameter considerably smaller than shell width → 16
15. Shell width equal to shell length → C. pusilla
– Shell width considerably smaller than shell length → C. pusilla conica
16. Shell length > 40 µm → 27
– Shell length < 40 µm → 17
17. Shell length 8–12 µm → 18
– Shell length > 12 µm → 20
18. Shell length > shell width → C. minuta
– Shell length < shell width → 19
19. Shell surface with scarce sand grains → C. patinata
– Shell surface smooth → C. bassini
20. Shell surface with scarce sand grains → 25
– Shell surface smooth → 21
21. Aperture large (diameter ≈ 1/3–1/4 of maximal shell width) → 23
– Aperture small (diameter ≈ 1/6–1/8 of maximal shell width) → 22
22. Aperture diameter 1.5–2.5 µm → C. leachi
– Aperture diameter 3.5–4.5 µm → C. vulgaris
23. Shell ovoid → 24
– Shell pyriform → C. crenulata glabra
24. Shell colorless → C. oviformis
– Shell yellowish‑brown → C. oviformis fusca
25. Shell subspherical; width/length ratio > 0.8 → C. horrida
– Shell elongated; width/length ratio < 0.7 → 26
26. Shell length 24–27 µm → C. voigti
– Shell length 20–24 µm → C. psammophila
– Shell length 17–21 µm → C. angusta
27. Shell length ≈ 40 µm; broadest width at mid‑shell → C. apiculata
– Shell length ≈ 55 µm; broadest width in upper third → C. valida
After Bobrov and Mazei, 2017