The Echinoid Directory

• Test ovate with shallow but distinct anterior sulcus on lower surface; posterior face vertically truncate. Oral surface with keel-like plastron.
• Apical disc with two gonopores (no gonopore on posterior genital plates). Genital plates 1 and 4 and ocular plates I and V uniserial and alternate.
• Ambulacra all similar; flush; pore-pairs rudimentary; apetaloid. Adapical plates almost as large as interambulacral plates.
• Peristome circular and close to the anterior; a shallow furrow leads to the anterior border but has disappeared by the ambitus.
• Plastron plating orthosternous with labral plate followed by a single large sternal plate then two pairs of elongate and symmetical plates.
• Interambulacra 1 and 4 meridoplacous; 2 and 3 amphiplacous.
• Periproct opening high on the posterior truncate face; ovate.
• Aboral tuberculation fine.
• Marginal fasciole present passing subambitally around the anterior.

Recent, North of Bermuda.

Calymne relicta Wyville Thomson, 1877, p. 397, by original designation.

• Only the type species.

Holasteroida, Meridosternata, Stegasterina, Calymnidae.

Monotypic.

This taxon has recently been described on the basis of new, well preserved tests by Saucede et al. (2009)

The syntypes were already fragmented by 1881, when Agassiz redescribed them. No other material is known. It comes closest to Sternopatagus in form, differing from this and all other Calymnidae in having uniserially arranged plating in the posterior part of its apical disc, and in having just two gonopores.

Saucede, T., Mironov, A. N., Mooi, R. & David, B. 2009. The morphology, ontogeny, and inferred behaviour of the deep-sea echinoid Calymne relicta (Holasteropida). Zoological Journal of the Linnean Society 155, 630-648.

Smith, A. B. 2004. Phylogeny and systematics of holasteroid echinoids and their migration into the deep-sea. Palaeontology 47, 1-28.

Wyville Thomson, C. 1877. The voyage of "The Challanger" The Atlantic...  MacMillan & Co.