The Echinoid Directory

• Test small (less than 25 mm diameter), low and subconical, oral side flattened.
• Apical disc very large, dicyclic; genital plates pentagonal, ocular plates projecting and subtrigonal. Periproct opening small and central, circular, with four anal valve plates. Gonopores ?undeveloped in known specimens. Disc covered in small pustules.
• Ambulacra trigeminate, with small pore-pairs, uniserially arranged; adorally expanding into a short phyllode.
• Ambulacral plating not clear, probably arbaciid with all elements extending to perradius on adapical plates. Primary tubercle to each compound plate except on most adapical.
• Interambulacral plates wide; primibasal plate present but small and not prolonged and not with a median primary tubercle.
• Aboral plates without primary tubercles, but each with a row of non-articulating pegs, forming horizontal bands.
• On oral surface two primary tubercles on interambulacral plates; the outer series of which continue a little above the ambitus.
• Primary tubercles imperforate and non-crenulate.
• Peristome about half test diameter; buccal notches rather wide and open, with small lip but no tag.
• Spines flattened, with distal glassy cap.

Recent, Caribbean, Indo Pacific.

Dialithocidaris gemmifera Agassiz, 1898, p. 258, by original designation.

• D. gemmifera Agassiz, 1898; Recent, Hawaii.

Euechinoidea, Echinacea, Arbacioida, Arbaciidae.

Distinguished from Codiopsis by having pustules on aboral plates forming horizontal series.

Agassiz, A. 1898. Reports on the dredging operations of the west coast of Central America to the Galapagos; part 23, Preliminary reports on the Echini. Bulletin of the Museum of Comparative Zoology, Harvard College, 32, 7-86, pls 1-13.

Mortensen, T. 1935. A monograph of the Echinoidea II. Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C. A. Reitzel, Copenhagen.