The Echinoid Directory

Echinocystites Thomson, 1861, p. 106

[=Cystocidaris Zittel, 1879, p. 480 (objective); =Echinocystis Gregory, 1897, p. 124 (nomen vanum); ?=Wrighthia Pomel, 1869, p. 46, type species Palaechinus phillips ]

Diagnostic Features
  • Test shape circular and depressed?; plating thin and imbricate.
  • Apical disc small; with a single enlarged genital plate with hydropores.
  • Ambulacra narrow; quadriserial at ambitus and adorally, becoming uniserial adapically. Each plate with a single pore-pair centrally placed, and with marginal tubercle.
  • Internally perradial flanges enclose the radial water vessel. Large adradial extensions from adradial plates extend beneath adjacent interambulacral plates.
  • Interambulacral zones broad and composed of a large number of small, scale-like plates probably rather irregularly arranged. Individual plates with central primary tubercle that is perforate and non-crenulate; a few smaller secondary tubercles or granules around plate margin.
  • Peristome small; plating entirely ambulacral.
  • Lantern well developed with large grooved teeth composed of a biseries of elements in a V-shape.
  • Spines short, simple; present on ambulacral and interambulacral plates.
  • Primitive pedicellariae present consisting of three rods attached to a single tubercle.
Distribution
Upper Silurian (Ludlow), UK.
Name gender masculine
Type
Echinocystites pomum Thomson, 1861, p. 106, by subsequent designation of Gregory, 1897, p. 133.
Species Included
  • Only the type species.
Classification and/or Status

Stem group Echinoidea; Echinocystitidae.

Monotypic.

Remarks

Distinguished from Palaeodiscus by its quadriserial ambulacral plating. Close to Rhenechinus from which it differs only in having slighly more regularly polygonal interambulacral plates and smaller less obvious tuberculation. Gotlandechinus differs in having a uniserial arrangement of pore-pairs close to the perradius

Hawkins, H. L. & Hampton, S. M. 1927. The occurrence, structure , and affinities of Echinocystis and Palaeodiscus. Quarterly Journal of the Geological Society London 83, 574-603, pls 44-46.

Wyville Thomson, C. 1861 (January). Edinburgh New Philosophical Journal new series 13, p. 106.