The Echinoid Directory

• Test thick.
• Apical disc small; generally less than 40% test diameter. Plating dicyclic; densely covered in tubercles/spines. Genital plate 2 significantly larger than other genital plates.
• Interambulacra with between 5 and 9 plates in a series. Primary tubercles perforate and non-crenulate; areoles incised. Scrobicular tubercles differentiated and scrobicular rings separated except immediately beside the peristome where they may be confluent. Extrascrobicular zones poorly developed and with heterogeneous tuberculation.
• Ambulacra sinuate and moderately broad. Pore-pairs horizontal and well developed; the two pores conjugate and widely separated. Perradial tuberculation comprises a marginal primary and one or more slightly smaller inner secondaries.
• Peristome large (larger than apical disc); ambulacral plates quadriserial in each zone. Interradial plates confined to outer part of peristomial membrane only.
• Primary spines stout and weakly fusiform, tapering to a blunt point. Shaft ornamented by dense granules more or less regularly arranged, but not forming distinct ribs.
• Secondary spines flat, scale-like and strongly apressed.

Lower Miocene to Recent, Indo-Pacific.

Cidarites imperialis Lamarck, 1816, p. 54, by original designation.

• see Phyllacanthus.

Cidaroida, Cidaridae, Cidarinae.

Subjective junior synonym of Phyllacanthus Brandt, 1835.

Desor, E. 1855-1858. Synopsis des échinides fossiles, lxviii + 490 pp., 44 pls. Reinwald, Paris.

Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.

Philip, G. M. 1963. The Tertiary echinoids of South-East Australia. Proceedings of the Royal Society of Victoria 76, 181-236, pls 21-26.