Cyclopyxis penardi and C. eurystoma

 

 

Genus Cyclopyxis (Deflandre, 1929)

 

Diagnosis: Shell brown; in ventral view circular, in lateral view hemispherical; composed of agglutinated mineral particles; aperture central, invaginated, circular, sometimes with internal tube; few species with irregular or lobed pseudostome, margin never with thick organic lip but often with small mineral particles. Ventral surface usually smooth, dorsal part rough with larger sand grains.
More than 30 species and twice as many varieties. Type species: Cyclopyxis arcelloides (Penard, 1 902)

 

Ecology: sphagnum mosses, soil.

 

Common species:

Cyclopyxis eurystoma
Cyclopyxis kahli
Cyclopyxis intermedia

 

Key to the species:

 

Pseudostome circular
11
1'
Pseudostome with lobes or teeth
2
 
Pseudostome regularly lobed, without minute spines
3
2’
Pseudostome irregularly lobed with minute spines on the lobes
C. acmodonta
 
Test diameter < 200 µm
4
3'
Test diameter > 200 µm
10
 
Pseudostomal lobes or teeth with concave or convex sides
5
4'
Pseudostome cross-shaped, with rectangular edges
C. crucistoma
 
Test < 100 µm
6
5'
Test > 100 µm
C. grospietschi
 
Pseudostome with 3 lobes
7
6'
Pseudostome with 5, sometimes 3 or 4 lobes or teeth
C. stellata
 
Diameter of test < 80 µm
8
7'
Diameter of test > 80 µm
9
 
8'
Pseudostome regularly shaped
C. trilobata
8''
Pseudostome irregularly shaped
C. triquestrus
 
9  
Test diameter 87-125 µm
C. leidyi
9'
Test diameter 180-220 µm
C. machadoi
 
10
Pseudostome with 6-8 sharp teeth
C. impressa
10'
Pseudostome with 7 rounded teeth
C. lobostoma
 
11
Diameter of the test < 80 µm
12
11'
Diameter of the test > 100 µm
17
 
12
Test completely covered with diatoms
C. bacillifera
12'
Test covered with quartz particles
13
 
13
Test flattened, height/diam. ratio < 0.55
14
13'
Test hemispherical (height/diam. > 0.55)
15
13''
Test conical
C. tronconica
 
14
Diameter of pseudostome > 0.65 diameter of the test
C. plana
14'
Diameter of pseudostome is 0.5-0.6 diameter of the test
C. amplecta
14''
Diameter of pseudostome < 0.5 diameter of the test
C. plana microstoma
 
15
Height of test equal or larger than the diameter
16
15'
Height of test less than its diameter
C. eurystoma
 
16
Pseudostome slightly concave
C. eurystoma alta
16'
Pseudostome strongly concave
C. eurystoma sinuosa
 
17
Test hemispherical, pseudostome relatively large, > 1/3 test diameter
18
17'
Lateral sides of the test almost parallel; dorsal side in lateral view somewhat flattened, with large mineral particles often protruding from its sides; small mineral particles around the deep mouth
C. kahli
 
18
Test flattened
19
18'
Test hemispherical
20
 
19
The diameter of the mouth is about half the diameter of the shell
21
19'
Diameter of mouth is not more than 1/4 of the diameter of the shell
C. aplanata microstoma
 
20
Diameter of the test 180-210 µm
С. aplanata
20'
Diameter of the test 130 µm
C. eurystoma sinuosa
 
21
Diameter of the test 80-110 µm; pseudostome up to 1/2 the diameter of the test; surrounded by small, often shiny mineral particles, why it seems finely toothed
C. arcelloides
21’
Diameter of the test 330-380 µm; pseudostome > 1/2 of test diameter
C. penardi