Assulina muscorum Greeff, 1888
Diagnosis: shell usually brown, ovoid, laterally flattened, biconvex in cross-section, with overlapping elliptical scales, usually arranged in alternating diagonal rows or occasionally irregularly; aperture narrow oval, more or less crenulate with margin of organic cement; the amount of cement around the aperture varies, but is often pronounced. Plasma colorless with a median band of granules. Nucleus vesicular. Numerous vacuoles usually present. Pseudopodia filose, seldom branched, straight, radiating, and few in number.
Dimensions: Length 33-60 µm (Hoogenraad and De Groot, 1940); 28-58 µm (Cash et al., 1915); 45-53 µm (Ogden & Hedley, 1980)
Ecology: mosses and Sphagnum, soil; very common. Cosmopolitan.
Remarks: Although empty tests are nearly everywhere numerous, living animals are not very common, and active individuals are rarely observed. In situations where moss is liable to considerable desiccation, individuals are few and their tests are often distorted; a large proportion of the empty tests are found with the two sides pressed together; this weakness may be due to the lenticular shape of the tests in transverse section (Cash et al., 1915).