Netzelia oviformis (Cash, 1909) Ogden, 1979
Diagnosis: Shell elongate ovoid, usually yellow or brown in color; symmetrical and smooth with a broadly-rounded dorsal part; sides curving downwards to the rather narrow and usually tri- or four-lobed mouth which is furnished with an thick wavy lip or collar; shell constructed of flat mineral grains, fragments of diatom frustules and secreted siliceous idiosomes in assorted mixtures to give a smooth surface. Organic cement building units seen as part of general shell matrix, each unit having distinct pores on both inner and outer faces. Single, vesicular nucleus with central nucleolus, one contractile vacuole, cytoplasm not filling shell cavity; pseudopodia numerous simply branched.
Dimensions: Cash 110 µm long and 80 µm broad; other workers: 65-95 µm. My dimensions: 66-85 µm.
Ecology: Between waterplants and in mosses like Sphagnum; usually rare, but sometimes locally abundant.
Remarks: Usually the aperture is 3-5 lobed, but a two-lobed specimen has been reported by Bruce Taylor (pers. comm.). The aperture is surrounded by a thick layer of organic cement which obscures the necklace of small particles. This covering was described as “an expanded wavy collar of thin chitinous substance” by Cash (1905) and clearly figured by Ogden (1980).This rare species is easy to identify. I have seen it in material from the Kromme Rade in Kortenhoef, the Netherlands. In September 2012 I found a very rich population in an isolated forest pond in Baarn. The population occurred in debris on waterplants and all specimens had a four-lobed aperture. Within this population specimens with slender and broad ovoid shells occurred.