The Echinoid Directory

Echinostrephus A. Agassiz, 1863, p. 20

[=Perinatus A. Agassiz, 1872, p. 119, nomen nudum; =Raphidechinus Lambert & Thiery, 1914, p. 241, type species Echinus molaris de Blainville, 1815 ]

Diagnostic Features
  • Test circular in outline flat upper and lower surfaces in profile and ambitus above mid-height.
  • Apical disc dicyclic with only small granules; periproct relatively small.
  • Ambulacral plating with four pore-pairs to a plate forming arcs in type species. Primary tubercle to each plate occupying almost the entire area.
  • Pore-zones expanding slightly towards the peristome forming small phyllodes.
  • Interambulacral plates with row of subequal primary tubercles.
  • Aboral spines long and slender; ambital and adoral spines short.
  • Globiferous pedicellariae with single lateral tooth, no neck and tubular blade.
Distribution Recent; tropical Indo-Pacific.
Name gender masculine
Type Echinostrephus aciculatus A. Agassiz, 1863, by original designation.
Species Included
  • E. aciculatus A. Agassiz, 1863; Recent, Indo-West Pacific; 0-50 m.
  • E. molaris (de Blainville, 1815); Recent, Indo-West Pacific; 0-50 m.
Classification and/or Status Camarodonta; Echinoida; Echinometridae.

Remarks The high ambitus makes this genus instantly identifiable. It lives in reefal environments where it bores a living chamber for itself. It uses its aboral spines for defence and its aboral tube-feet to capture drift algae. Larger individuals may become trapped within their hole as they grow.

Although the two species differ in the number of pore-pairs incorporated into a compound plate (E. aciculatus has four, E. molaris three), they are similar in other respects and thus treated as congeneric.

Agassiz, A. 1863. List of echinoderms sent to different institutions in exchange for other specimens. Bulletin of the Museum of Comparative Zoology, Harvard College, 1 (2), 17-28.