I found this one in a sample from Crailoo, the Netherlands. It came up in a wet mount kept in a moist chamber for some days. There were only two specimen, attached to the underside of the coverslip. It is remarkable because of two things:
1 It has very few granules along its filopodia;
2 There is a dotted line around the cell body.
M. ovalistoma – after Bartos, 1963 Metaheleopera Bartos, 1963 Diagnosis: Shell clearly narrowing towards the pseudostome, which can be seen even more clearly on the narrower sides
M. radixicola – after Chardez, 1974 Matsakision radixicola Chardez, 1974 Diagnosis: Shell ovoid, slightly compressed, transparent; pseudostome oval, truncated perpendicularly, with a slight neck. Shell
M. cassagnaui – after Bonnet, 1967 Matsakision cassagnaui Bonnet, 1967 Diagnosis: Shell hyaline, elongated ovoid, very little compressed, truncated perpendicularly or very slightly obliquely in
Matsakision – after Bonnet, 1967 Matsakision Bonnet, 1967 Diagnosis: Shell hyaline, elongated ovoid, very little compressed, truncated perpendicularly or very slightly obliquely in the region
Arcella marginata, after Deflandre, 1929 Arcella marginata Daday, 1905 Diagnosis: Shell roughly hemispherical, rather overhanging, with a flattened, smooth edge. In dorsal view showing a
Arcella lobostoma, after Deflandre, 1929 Arcella lobostoma Deflandre, 1929 Diagnosis: Shell hemispherical. In ventral view, irregular circular outline, often a little elliptical; pseudostome irregularly lobed: