Order Spumellaria

Family Coccodiscidae

Didymocyrtis tetrathalamus (Haeckel) (Figure 2J, 15.77) [=Ommatartus tetrathalamus, Panartus tetrathalamus]. Cortical shell cylindrical to ellipsoidal with a very conspicuous equatorial constriction. Two medullary shells (outermost slightly compressed, innermost spherical) joined to the cortical by several radial beams confined to the equatorial plane. May have polar caps (Figure 2J) or spines, and supplemental peripheric growth (mantle; Figure 15.77). Height of cortical shell: 100-150 µm; height of polar cap: 40-65 µm. Ref: Nigrini and Moore (1979).

Spongoliva ellipsoides Popofsky (Figure 15.76). Generally similar to D. tetrathalamus, except that cortical shell is a much looser and irregular meshwork. Fully grown specimens usually have a well developed mantle. Height of cortical shell: 100-250 µm. Ref: Benson (1966).