The Echinoid Directory

• Test plating rather thin and fragile, although plating effectively sutured throughout.
• Apical disc monocyclic. Large circular periproct with enlarged periproctal plates peripherally; genital plates projecting strongly interradially.
• Ambulacra narrow and straight; pore-pairs non-conjugate. Pore-pairs uniserial in smaller individuals, but with every third pore-pair insert in larger individuals. Adorally pore-pairs become more crowded to form phyllodes.
• Ambulacral plating trigeminate with single large primary tubercle only on every second or third plate in adults.
• Interambulacral zone wide, with ambital plates very much wider than tall.
• Multiple subequal primary tubercles on ambital interambulacral plates; tubercles perforate and crenulate.
• Peristome relatively small, with rounded buccal notches associated with adradial tags.
• Spines long and slender with verticillate ornament; axial lumen filled with a sparse open network.

Recent, Indo-Pacific and Caribbean.

Cidaris radiata Leske, 1778, by original designation.

• A. radiata (Leske, 1778); Recent, Indo-West Pacific.
• A. pulvinata (Lamarck, 1816); Recent, west coast of America.
• A. magnifica A. H. Clark, 1934; Caribbean.

Diadematoida; Diadematidae.

Presumed monophyletic.

Differs from Diadema in having a monocyclic disc, in having the smooth, adapical naked zone forked and extending to the ambitus, and in having ambulacral compound plates of different size.

Gray, J. E. 1825. An Attempt to divide the Echinida, or Sea Eggs, into Natural Families. Annals of Philosophy, new series 10, 423-431.

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