The Echinoid Directory

• Test relatively thin and fragile; none exceeding 30 mm in test diameter.
• Apical disc very large (65-75% test diameter); raised; strongly dicyclic; covered in tubercles, but with a bare edge to the plates. Relatively few periproctal plates. Ocular pores surrounded by a distinct rim.
• Interambulacral tubercles perforate and non-crenulate; areole not sunken. Scrobicular tubercles hardly differentiated from other granulation.
• Median interradial suture zone rather bare and slightly sunken; small pits at adradial end of horizontal interambulacral sutures.
• Ambulacra narrow; composed of relatively few plates. Pore-pairs very narrow with only a thin interporal partition, or the two pores coalesced; strongly oblique to the plate suture.
• Peristome about half test diameter; relatively few ambulacral plates in each series (less than 10).
• Primary spines long, cylindrical and slender with short collar and distinct neck; terminating in a simple point. Shaft of spine with semiregular rows of thorns with scattered fine hairs in between.
• Oral spines spear-shaped and with serrated margins.
• Secondary spines erect and cylindrical, not adpressed around the base of the primary spines.

Recent, Antarctic and Pacific deep sea.

Porocidaris milleri Agassiz, 1898, p. 74, by original designation.

• A. milleri (Agassiz, 1898); Recent, East Pacific.
• A. fragilis Agassiz & Clark, 1907; Recent, North Pacific.
• A. antarctica Mortensen, 1909; Recent, Antarctic.
• A. incerta (Koehler, 1902); Recent, southern tip of South America.
• A. eltaniana Mooi et al. 2000; Recent, Antarctic.
• A. usarpi Mooi et al. 2000; Recent, Antarctic.

Cidaroida, Ctenocidaridae

Differs from Ctenocidaris by the larger size of its apical disc and its adoral interradial sutures which are rather bare.

Agassiz, A. & Clark, H. L.  1907. Hawaiian and other Pacific Echinoids. Memoirs of the Museum of Comparative Zoology at Harvard College  34(1), 1-42, pls 1-44.

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

Caso, M. E. 1979. Los equinoideos del Pacifico de Mexico. Parte Primera - Ordenes Cidaroidea y Aulodonta. Publicaciones especiales Centro de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico 1, 1-103.

Mooi, R., David, B., Fell, F. J. & Chone, T. 2000. Three new species of bathyal cidaroids (Echinodermata: Echinoidea) from the Antarctic region. Proceedings of the Biological Society of Washington 113, 224-237.