Pyxidicula
Pyxidicula patens - 39 µm

 

 

Genus Pyxidicula Ehrenberg, 1938

 

Diagnosis: shell patelliform or hemispherical, more or less rigid, transparent, speckled; aperture circular, almost the entire diameter of test, or somewhat contracted by an inward margin; a single nucleus; one or more contractile vacuoles.

 

1 Shell hemispherical 2
- Shell flattened, like a disc 4
2 Aperture with a narrow recurved margin P. operculata
- Aperture with two narrow margins or collars, one curved inwards, the other curved outwards 3
3 Outer collar broader than the inner rim, hyaline, thinner than the rest of the shell and somewhat undulated P. patens
- Both collars relatively small with the same structure and color as the rest of the shell, not undulated Pyxidicula spec.
4 Shell with a flat margin P. cymbalum
- Shell with a hollow or tube shaped margin P. invisitata

 

 

Pyxidicula operculata - drawing by Hoogenraad & De Groot 1940