(Müller, 1858)
Shell ovoid, very thick-walled. All 20 spicules of nearly equal form, 2 main slightly longer and thicker. Crests between dimples of shell-wall serrated; cornets around spicules short, with regularly spiny edges. Shell diameter: 0.38-0.4 mm (0.17-0.2 mm according to Haeckel, 1887); length of main spicules: 0.14-0.19 mm, secondary: 0.12-0.15 mm.