Haeckel, 1881
Lenticular, biconvex, latticed cortical shell, not surrounded by spongy or chambered structures, within which a small, spherical single or double medullary shell is enclosed. The margin (but less commonly the surfaces) of the cortical shell may bear radial spines.
The following species of this family are treated in the present volume:
Heliodiscus asteriscus
Sethodiscus macrococcus