The Echinoid Directory

• Test rather flatterned; plating rather thin, plating flexible, especially along adapical interradial suture.
• Apical disc hemicyclic with posterior oculars insert; periproct with larger plates around periphery.
• Ambulacral straight; about one-third of interambulacral width; pore-pairs non-conjugate; uniserial throughout.
• Ambulacral plating pseudocompound with single large primary tubercle on every third plate which is enlarged compared to the others.
• Interambulacral zone composed of elongate plates with one or two primary tubercles; plates wider than tall; plates rather naked.
• Primary tubercles perforate and weakly crenulate.
• Peristome with shallow, broad, rounded buccal notches.
• Spines slender, smooth and hollow.

Recent, Hawaii.

Leptodiadema purpureum Agassiz & Clark, 1907, by original designation.

• Only the type species.

Diadematoida; Diadematidae.

Subjective junior synonym of Lissodiadema Mortensen, 1903.

Based on a single individual 9 mm in diameter. Mortensen (1940) considered it highly likely that it was identical to Lissodiadema, the differences being almost entirely attributable to the small size of the specimen.

Mortensen, T. 1940. A monograph of the Echinoidea. Volume III. 1, Aulodonta. C. A. Reitzel, Copenhagen.

Agassiz, A. & Clark, H. L. 1908. Preliminary report on the Echini collected, in 1902, among the Hawaiian Islands, by the U.S. Fish Comussion steamer "Albatross", in charge of Commander Chauncey Thomas, U.S.N., commanding. Bulletin of the Museum of Comparative Zoölogy at Harvard College, 50/8: 231-259.