world of amoeboid organisms

Shell with flattened top and aperture with crenulated border; usually with six ribs.

Shell with six or more ribs; dorsal surface with ribs and depressions; aperture smooth, without crenulations.

Shell in side view trapezoid, with six or more ribs; aperture smooth without crenulations.

Shell with basal border. Dorsal surface with depressions. Diameter c. 80-110 µm.


Shell with basal border. Dorsal surface with depressions. Diameter c. 80 µm. 


Shell in lateral view hemispherical, with acute or somewhat rounded corners,  sometimes with a basal border. Diameter c. 35-55 µm. 

Shell hemispherical, with smooth and broad rounded corners in lateral view. 


Shell with distinct basal border. Ratio diameter aperture/shell 0.2.

Arcella crenulata
Arcella crenulata

Shell dome shaped; aperture with irregular crenulated border.       

Arcella excavata

Shell formed like a saddle. Aperture elliptical.       

Shell balloon shaped.       

Test broader than high; height c. 80-90 µm.  

Shell with undulations, more or less spherical. 

Shell spherical, wrinkled.       


Shell shaped like an old hat.

Arcella formosa

Shell resembling a pie; prominent folds or ribs often with darker color.       

Arcella brasiliensis

Shell with striated border


Shell border with numerous small spines.

Arcella multilobata


Shell flattened, with crenulated aperture.


Shell crowned with some spines.


Shell with high dome and distinct neck.

Arcella gandalfi


Shell like Gandalf’s hat.


Shell sub-hemispherical, round smooth aperture, thickened edges

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Valkanovia delicatula

V. delicatula, after Valkanov, 1962 Genus Valkanovia  Tappan, 1966 Diagnosis: Shell ovoid, oblate, elliptical in cross-section, composed of elongated elliptical hyaline scales arranged in a

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Gocevia pontica

Gocevia pontica, after Valkanov, 1934 Gocevia pontica Valkanov, 1934 Diagnosis: Clearly addressed bipolarity. Body covered by a weakly flexible tectum covered with foreign bodies. The

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N. brevis, after Snegovaya and Alekperov, 2009 Genus Nabranella Snegovaya and Alekperov, 2009 Diagnosis: Shell oval or spherical shape without neck. Apical top flat and

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Genus Armipyxis Dekhtiar, 2009 Genus Armipyxis was created by Dekhtiar (2009) to accommodate all species with internal struts. However, C. aculeata may also have struts, although

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Netzelia pseudolimnetica

N. pseudolimnetica, after Penard, 1902 Netzelia pseudolimnetica Ogden and Meisterfeld, 1989 Synonym Difflugia limnetica (Levander, 1900) Penard, 1902. D. limnetica – Pejler, 1962, Oikos, 12,

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Cylindrifflugia hiraethogii

C. hiraethogii, after Ogden. 1983 Cylindrifflugia hiraethogii (Ogden, 1983) González-Miguéns et al., 2022 Diagnosis: the shell is light yellow or transparent, thin pyriform with a distinct

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Cylindrifflugia bacillariarum

  C. bacillariarum, 103 – 114 µm – Fochteloërveen, Netherlands   Cylindrifflugia bacillariarum (Perty, 1849) n. comb. González-Miguéns et al., 2022 Diagnosis: shell transparent, colorless or

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Cylindrifflugia elegans

C. elegans, length 84-102 µm, Gaasterland Cylindrifflugia elegans (Penard, 1890) n. comb. González-Miguéns et al., 2022 Basionym: Difflugia elegans Penard, 1890 Diagnosis: shell outline rough, pyriform

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Cylindrifflugia lanceolata

C. lanceolata, shells 153-169 µm long, nuclei 23-26 µm (Naardermeer, Netherlands) Cylindrifflugia lanceolata (Penard, 1890) n. comb. González-Miguéns et al., 2022 Basionym: Difflugia lanceolata Penard,

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