The Echinoid Directory

• Test flattened above and below; relatively small.
• Apical disc about half the test diameter; monocyclic. Plates uniformly covered in dense granules. All five genital plates similar in size. Sexual dimorphism in gonopore size.
• Interambulacrum with 7-9 plates in a series. Primary tubercles perforate, non-crenulate. Areoles ovate and incised; scrobicular circles contiguous or confluent throughout.
• Scrobicular tubercles differentiated. Extrascrobicular areas not extensive; secondary tubercles dense and arranged into horizontal rows.
• Interradial suture distinctly incised as is the ambulacral perradial zone to a lesser extent.
• Ambulacra weakly sinuous. Pore-pairs conjugate with moderately wide interporal partition; pore zones sunken. Perradial zone wider than pore zones with marginal series of contiguous primary tubercles and inner series of smaller tubercles.
• Peristome slightly smaller than the apical disc. Ambulacral plates uniserial; interambulacral series not reaching the mouth.
• Primary spines long, with short collar and neck; tapering to a point. Shaft strongly thorned; covered in fine cortical hairs that coalesce to form an outer surface. Secondary spines flattened.

Recent, Indo-West Pacific.

Schizocidaris assimilis Mortensen, 1903, p. 25, by original designation.

• S. fasciata Mortensen, 1927; Recent, Sulu Island.
• S. assimilis Mortensen, 1903; Recent, Malay Archipelago.
• S. serrata (Mortensen, 1903); Recent, Philippines.

Cidaroida, Cidaridae, Goniocidarinae.

Presumed monophyletic.

Differs from Goniocidaris in the form of its spines which lack disc-like elements and the very distinctive secondary crust formed by cortical hairs. It lacks well defined sutural pits.

Mortensen, T. 1903. The Danish Ingolf-Expedition volume 4 (1) Echinoidea, Part 1, pp. 1-198, pls 1-21.

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