The Echinoid Directory

• Test globular, typically large; plating thick and tesselate.
• Apical disc small; monocyclic.
• Ambulacra more or less straight and almost as wide as the interambulacral zones; basically quadriserial throughout. An outer and and inner series of plates in each half ambulacrum; each plate with a small pore-pair so that pore-pairs form four vertical, widely separated bands in each zone. However, a few additional occluded plates occur between so that some pore-pairs are found in between the two columns.
• Interambulacral zones wide; composed of up to 9 regular columns of polygonal plates.
• Interambulacral plates with granulation only; no primary tubercle.
• Peristome small, plating unknown.
• Lantern and spines unknown.

Lower Carboniferous, USA, ?Australia.

Melonites danae Meek & Worthen, 1861, p. 397, by original designation.

• O. danae (Meek & Worthen, 1861); Keokuk Group, Lower Carboniferous, USA.
• O. blairei Miller & Gurley, 1893; Keokuk Group, Lower Carboniferous, USA.
• O. coreyi Meek & Worthen, 1870; Keokuk Group, Lower Carboniferous, USA.
• O. sulcatus Miller & Gurley, 1893; St Louis Group, Lower Carboniferous, USA.
• O. halli Jackson, 1912; Keokuk Group, Lower Carboniferous, USA.

Stem group Echinoidea; Palaechinidae.

Presumed monophyletic.

The test is very similar in form to Melonechinus, but the pore-pairs form four distinct, widely spaced columns, not the dense, continuous adradial bands of pore-pairs of that genus.

Jackson, R. T. 1912. Phylogeny of the Echini, with a revision of Palaeozoic species Memoirs of the Boston Society of Natural History 7, 491 pp. 76 pls.

Jackson, R. T. 1896 Geol. Soc. America Bull 7, p. 190, pl. 6, fig. 30.

Meek, F. B. & Worthen, A. H. 1861. Description of new Carboniferous fossils from Illinois and other western states. Proceedings of the Academy of Natural Sciences of Philadelphia 12:447-472 [for 1860, published January 1861]