After Young et al. 2003. XCs - circular, wheel-like, (2.5-3.5 μm); flat; broad rim; radial cycle well-developed, showing sinistral obliquity in distal view; central plate +/- square, formed of two overlapping elements.
BCs - elliptical (1.5 - 2.5 μm) wall flaring, with characteristic vertical ribs on outer surface, flat-topped (non-corrugated); low mound in centre. CFCs with strong spine, ca. 1.3 μm high.
Tropical - transitional (Findlay & Giraudeau, 2000).
60°03.1911' S, 150°47.9310' E, R. van den Enden, AAD, unpub.
HOL ?= Helladosphaera cornifera, see Cros et al.(2000)