The Echinoid Directory

• Test small, subpentagonal, depressed in profile.
• Apical disc very small; plate details uncertain.
• Ambulacra narrow and biserial over the aboral surface, expanding markedly just above ambitus and becoming multiserial over the oral surface. Adoral plates large, with large, rounded pore-pairs.
• Interambulacral zones wide; composed of 5 or 6 columns of subhexagonal, imbricate plates. Plates somewhat variable in size and not forming well defined en-chevron rows. Adradial plates with small primary tubercle.
• Spines relatively short, stout and straight, without cortex or ornament.

• P. biserialis McCoy, 1849; Lower Carboniferous, Ireland.
• P. illinoisensis Worthen & Miller, 1883; Lower Carboniferous, USA.
• P. tesselatus (Jackson, 1912); Lower Carboniferous, USA

Stem group Echinoidea; Proterocidaridae.

Presumed monophyletic.

The biserial arrangement of the adapical ambulacra distinguishes this genus from other Protocidaridae other than Hyattechinus and in that genus the ambulacra, though expanding adorally, remain biserial to the peristome. It is very similar to Lepidechinus but differs in having adradial interambulacral plates bearing primary tubercles.

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.

M\'Coy, F. 1849. On some new palaeozoic echinodermata. Annals and Magazine of Natural History series 2, 3, 244-254.