The Echinoid Directory

• Test flattened below and domed above; circular to slighly pentagonal in outline.
• Apical disc small, dicyclic. Genital plates large and pentagonal; ocular plates smaller and protruding a little. All plates more or less bare, decorated by epistroma. Periproct large and subcircular.
• Ambulacra straight, expanding to ambitus; generally rather inflated; aboral pore-pairs uniserial, presumably conjugate and enlarged adapically, small and oblique adorally, where the pore zone expands to form short phyllodes.
• Plating in arbaciid triads adorally but apparently polygeminate at ambitus and above with four or five pore-pairs to a compound plate. Details of plate compounding not known. Each plate dominated by a single large tubercle from apex to peristome.
• Interambulacra a little wider than ambulacra. Above ambitus plates differentiated into an interradial sunken and naked zone, without tubercles and with just epistroma, and an outer, adradial band. A vertical ridge marks the boundary between the two zones, and this bears small peg-like structures. Adradially there is a small primary tubercle on each plate.
• Below the ambitus interambulacral plates with two subequal primary tubercles.
• Primary tubercles with massive imperforate mamelon and no platform. The areole forms a slightly raised platform on the plate.
• Peristome subcircular or subpentagonal, large (about half test diameter). Buccal notches shallow.
• Spines unknown.

Coelopleurus spinosissimus Agassiz, in Agassiz & Desor, 1847, p. 53 [=Coelopleurus radiatus Agassiz, in Agassiz & Desor, 1847, p. 53] by monotypy.

• Only the type species.

Euechinoidea, Echinacea, Arbacioida, Arbaciidae.

Subgenus of  Coelopleurus Agassiz, 1846.

If the diagrams in Cotteau (1893) are to be believed this taxon differs from all other Coelopleurus in having polygeminate rather than trigeminate ambulacral plating. However, no material of this species has been examined and Cotteau's figures are known to be unreliable.

Cotteau, G. 1889-94. Paleontologie francaise. Terrain Tertiaires. Eocene Echinides 2. G. Masson, Paris.

Pomel, A, 1883. Classification methodique et genera des echinides vivants et fossils. Alger, Paris.