world of amoeboid organisms


Aperture usually surrounded by pores. Aperture diameter 0.45 of shell diameter. Shell diameter 70-160 µm.

Aperture surrounded by pores. Aperture diameter ≥ 0.4 of shell diameter. Shell very flat; diameter 140-402 µm.

Aperture surrounded by pores. Distinct basal rim. Height ca 1/3 of shell diameter.

Shell elliptical, quadrate or circular. Shell often with distinct dorsal folds or ribs. Aperture small and with pores.       

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

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

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


Shell in lateral view trapezoid, with 5-7 ribs. Aperture with pores.

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 with a number of projections.


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

Recent posts

Zivkovicia compressoidea

Z. compressoidea, a-b after Chardez, 1958; c after Jung, 1942 Zivkovicia compressoidea  (Jung, 1942) new.comb. Basionym: Pontigulasia compressoidea Jung, 1942 Diagnosis: Shell ovoid and compressed,

Read More »

Zivkovicia flexa

Zivkovicia flexa, from Cash and Hopkinson, 1909 Zivkovicia flexa  (Cash and Hopkinson, 1909) Ogden, 1983 Basionym: Pontigulasia compressa var. flexa  Cash and Hopkinson, 1909 Diagnosis:

Read More »

Lagenodifflugia epiouxi

L. epiouxi, after Chardez, 1984 3 Lagenodifflugia epiouxi (Chardez, 1983) new comb. Basionym: Pontigulasia epiouxi Chardez, 1983 Diagnosis: Shell elongate, circular in cross-section or very

Read More »

Centropyxis lapponica

Centropyxis lapponica, after Grospietsch, 1954 Centropyxis lapponica  Grospietsch, 1954 Diagnosis: Shell nearly circular in circumference, without spines. Aperture clear square with rounded corners. Shell viewed

Read More »

Chaos spec. 6

Chaos spec., Crailoo, 2021 Chaos spec. This specimen was found in a samples from Crailoo, Netherlands. It was remarkable because of the absence of crystals.

Read More »

Bullinularia maxima

Bullinularia maxima – from Bobrov and Mazei, 2020 Bullinularia maxima Bobrov et Mazei, 2020 Diagnosis: Shell brown, opaque, elliptical in ventral view; ventral surface is

Read More »

Bullinularia macroporum

Bullinularia macroporum – from Bobrov and Mazei, 2020 Bullinularia macroporum Bobrov et Mazei, 2020 Diagnosis: Shell yellow-brownish, transparent, circular in ventral view; ventral surface is

Read More »

Nebela golemanskyi

N. golemanskyi, after Todorov, 2010 Nebela golemanskyi Todorov, 2010 Diagnosis: Shell large, colourless and pyriform, with a distinct short neck about one fourth of the

Read More »

Nebela nebeloides

N. nebeloides, after Gauthier-Lièvre and Thomas, 1958 Nebela nebeloides (Gauthier-Lièvre and Thomas, 1958) Todorov et al., 2010 Basionym: Difflugia nebeloides Gauthier-Lièvre and Thomas, 1958 Diagnosis:

Read More »