Sphaeriodiscus Fisher 1910

Sphaeriodiscus Fisher, 1910: 171; 1911: 167; Tortonese & A.M. Clark, 1956: 343; Halpern, 1970b: 79; A.M. Clark & Courtman-Stock, 1976: 249; Clark & Downey, 1992: 265; H.E.S. Clark & McKnight, 2001: 133.

Diagnosis

Body pentagonal. Abactinal plates weakly tabulate, covered by evenly distributed granules. Marginal plates few, tumid with swollen or enlarged penultimates. Pedicellariae spatulate. Modified from Clark & Downey (1992).

Comments

The difficult distinction between Sphaeriodiscus and Peltaster has been outlined elsewhere (e.g. Mah 2011, 2018) with difficulties lying in the variable diagnostic character, the enlarged penultimate marginal plates.