The Echinoid Directory

Enallaster d'Orbigny, 1855, p. 181

Diagnostic Features
  • Test ovate with distinct anterior sulcus; posterior face truncate. Test subquadrate in outline, longer than wide.
  • Apical disc ethmophract with four gonopores.
  • Anterior ambulacrum sunken; pore-pairs heterogeneous, formed of a mixture of elongate \'petal-type\' pores and smaller circumflexed pore-pairs.
  • Other ambulacra petaloid. Anterior petals flexed forwards, with pore-pairs in posterior column much better developed than those in anterior column. Posterior petals much shorter and straighter.
  • Peristome subcircular and facing downwards.
  • Labral plate relatively large and triangular; longer than wide. Sternal plates subequal.
  • Periproct towards top of posterior truncate face.
  • No fascioles, although a band of denser and more aligned granules occurs between the ambitus and a zone level with the ends of the petals.
  • Aboral tubercles small and scattered; set in a groundmass of fine granules.
The type species comes from the Albian of England.
Name gender masculine
Hemipneustes greenovi Forbes, 1852, by original designation.
Species Included
Classification and/or Status

Spatangoida, stem group (toxasterids).

Subjective junior synonym of Heteraster d'Orbigny, 1855.

Remarks d'Orbigny, A. 1854-60. Paléontologie Française. Terrains Crétacés. Tome 6. Echinodermes, Échinoides irréguliers. 596 pp, pls 801-1006. G. Masson, Paris. 1-32 (July 1854); 33-64 (Oct. 1854); 65-96 (Nov. 1854); 97-128 (Jan. 1855); 129-192 (Mar. 1855); 193-208 (May 1855); 209-224 (Aug. 1855); 225-272 (Nov. 1855); 273-320 (Oct. 1856) pp. 273-352 (Oct. 1856), pp. 353-384 (1857), pp. 385-400 (1858), pp. 401-432 (1858), pp. 433-596 (1860).