Trinema lineare Penard, 1890

Diagnosis: Shell elliptic, oval in transverse section; shell composed of approximately fifty, large, circular, incompletely overlapping, shell-plates, and an unknown number of small, oval to circular, shell-plates which either haphazardly fill the interstices or are completely overlaid by the large shell-plates; shell plates hardly visible in bright field; aperture normally circular, invaginated and situated sub-terminally, bordered by an inner circle of from 18 to 28 small, denticulate apertural-plates and one or two rows of small shell-plates; apertural-plates may occasionally be moved from their marginal position to form double rows, or to be displaced out of symmetry. Nucleus with a central nucleolus.

Dimensions: My measurements: Length 17.4—31.7 µm; width 7.7—13.0 µm; depth 8.6—12.2 µm; aperture 3.0—6.5 µm; large scales 3.0—5.5 µm.

Habitat: Mosses, Sphagnum, aquatic vegetation, moistened soils. Generally distributed and apparently the commonest form of all Rhizopoda.

Remarks: Cash et al. (1915), Chardez (1956, 1970) and Thomas (1958) have illustrated variation in the position of the aperture, including examples of invaginated apertures. Whilst, in clonal cultures several abnormal forms have been observed (Hedley and Ogden, 1974)