The Echinoid Directory

• Test inflated and pentagonal in outline; plating rather fragile and slightly flexible.
• Apical disc hemicyclic with posterior oculars insert; periproct large and without distinct plates.
• Ambulacra narrow and straight; pore-pairs non-conjugate. Uniserial and in triads at ambitus and aborally but more irregular and widely spaced adorally.
• Ambulacral plating trigeminate at ambitus large primary tubercles variably developed - not forming a strict biseries. Adoral ambulacra with irregular scattering of dense granulation, but distinct primary tubercles.
• Interambulacral zone wide, with ambital plates distinctly wider than tall.
• Up to eight primary tubercles on ambital plates; all tubercles perforate and crenulate.
• Aboral surface almost naked; oral surface highly granular.
• Peristome relatively small.
• Spines long and slender (at least diameter of test); hollow, with verticillate ornament.

Recent, Mauritius.

Goniodiadema mauritiense Mortensen, 1939, by original designation.

• Only the type species.

Diadematoida; Diadematidae.

Monotypic.

Differs from Chaetodiadema in having a pentagonal test outline, with the angles of the pentagon interradial and in having compound triads with primary tubercles clearly continuing to the peristome. It is extremely similar to Eremopyga Agassiz & Clark, and possibly should be synonymized.

Mortensen, T. 1940. A monograph of the Echinoidea. Volume III. 1, Aulodonta. C.A. Reitzel, Copenhagen