The Echinoid Directory

• Test shape probably subspherical; plating thin and imbricate.
• Apical disc unknown.
• Ambulacra narrow; biserial. Plates with a single large, oval zone of small perforations occupying most of the exposed ambulacral plate and leaving almost no perradial zone.
• Internally large adradial extensions from adradial plates extend beneath adjacent interambulacral plates. Radial water vessel probably enclosed by perradial flanges.
• Interambulacral zones wider than ambulacral zones; composed of numerous small scale-like plates irregularly arranged.
• No primary tubercles, but all plates covered in small granules.
• Lantern present; teeth wide and flattened and composed of a double series of elements that give the tooth a V-shaped pattern.

Upper Ordovician (Ashgill), Scotland.

Eothuria beggi MacBride & Spencer, 1938, by original designation.

• Only the type species.

Stem group Echinoidea; Eothuriidae.

Monotypic.

Distinguished from all other Palaeozoic echinoids by its distinctive pore morphology. No other echinoid has ambulacral pores that comprise an oval area bounding some 12 small pores. Although MacBride & Spencer (1938) proposed this to be a holothurian, it seems to have more similarity to other primitive echinoids such as Aulechinus.

MacBride, E. W. & Spencer, W. K. 1938. Two new Echinoidea, Aulechinus and Ectinechinus, and an adult plated holothurian, Eothuria, from the Upper Ordovician of Girvan, Scotland. Transactions of the Royal Society, London B229, 91-136, pls 10-17.