The Echinoid Directory

• Test large and depressed; oral surface flat.
• Apical disc hemicyclic.
• Ambulacral plating polygeminate with 6 or 7 pore-pairs to a compound plate at ambitus and above, but fewer and more crowded adorally.
• Oral surface completely flat with relatively small peristome and wide highly developed phyllodes.
• Pore-pairs forming strongly oblique lines on each plate.
• A single primary ambulacral tubercle to each plate.
• Interambulacral plates with primary tubercle and large secondary tubercles, not forming horizontal rows.
• No naked zones aborally.
• Buccal notches shallow, but with prominent tags.
• Auricles fused perradially.

Recent; Japan.

Toxocidaris depressa A. Agassiz, 1863, by original designation.

Only the type species.

Euechinoida, Echinoida, Strongylocentrotidae

Monotypic.

Easily distinguished from other toxopneustids by its subhorizontal arcs of pore-pairs some 6 or 7 to a plate. Biochemical work has shown that this taxon is closer to strongylocentrotids (N. Matsuoka 1987 Zoological Science 4, 339-347) and its ambulacral structure suggests sister group relationships with Hemicentrotus which differs in having rather less pronounced buccal notches without the tags.

Mortensen, T. 1903. The Danish Ingolf-Expedition 1895-1896. Vol. 4, No. 2. Echinoidea, pt. 1.Copenhagen, 198 pp.

Mortensen, T. (1943) A monograph of the Echinoidea Part III.2, Camarodonta 1. C. A. Reitzel, Copenhagen