The Echinoid Directory

Echinodiadema Verrill, 1867, p. 580

Diagnostic Features	Test plating rather fragile, although plating effectively sutured throughout. Apical disc hemicyclic with ocular plates II and III exsert. Large circular periproct without enlarged periproctal plates. Genital plates projecting interradially; ocular plates almost as large as genital plates. Ambulacral narrow and straight; pore-pairs non-conjugate; uniserial but crowded adorally to form phyllodes. Ambulacral plating trigeminate with single large primary tubercle per plate. Interambulacral zone with ambital plates rather pentagonal with a single primary tubercle. Primary tubercles on ambital plates flanked by interradial row of small secondary tubercles; all tubercles perforate and crenulate. Peristome much larger than apical disc, with deep, rounded buccal notches associated with adradial tags. Spines very long and slender; hollow, with verticillate ornament.
Distribution	Recent; Gulf of California.
Name gender	neuter
Type	Echinodiadema coronata Verrill, 1867, by original designation.
Species Included	Only the type species.
Classification and/or Status	Diadematoida; Diadematidae. Subjective junior synonym of Centrostephanus Peters, 1855.
Remarks	Differs from Centrostephanus longispinus, the type of Centrostephanus, only in having primary ambulacral and interambulacral tubercles better developed adapically and in having a smaller apical disc. Mortensen, T. 1940. A monograph of the Echinoidea. Volume III. 1, Aulodonta. C.A. Reitzel, Copenhagen. Verrill, 1867-1871. Notes on the Radiata in the Museum of Yale College, with description of new genera and species. Transactions Conn. Acad. 1-9.