The Echinoid Directory

Pygomma Troschel, 1872, p. 309

Diagnostic Features	Similar to Arbacia punctulata (Lamarck, 1816) but with aboral spines short and club-shaped.
Distribution	Recent, west coast of South America.
Name gender	neuter
Type	Echinus spatuliger Valenciennes, 1846, by original designation.
Species Included	Only the type species.
Classification and/or Status	Arbacioida, Arbaciidae. Subjective junior synonym of Arbacia Gray, 1835.
Remarks	Troschel (1872) used this genus to distinguish those forms of Arbacia that have one or more ocular plates insert in the apical disc. As shown by Jackson (1927) this feature is very variable within species and provides no basis for taxonomic distinction. Mortensen, T. 1935. A monograph of the Echinoidea II. Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C. A. Reitzel, Copenhagen. Troschel, F. H. 1872. Die Familie der Echinocidariden (1). Archiv für Naturgeschichte 38, 293-356