The Echinoid Directory

Thylosalenia Pomel, 1883, p. 102

Diagnostic Features
  • Apical disc not raised above the corona; smooth. Posterior genital plate U-shaped, disc hemicyclic.
  • Periproct displaced towards posterior along anterior-posterior axis; two or three suranal plates incorporated into the disc.
  • Ambulacral plating trigeminate with a small marginal tubercle over two of every three elements aborally; primary tubercles slightly larger adorally. Granulation developed between the two columns of primary tubercles.
  • Adapical interambulacral plates without primary tubercle; covered in uniform granulation.
  • All tubercles perforate and crenulate; mamelons relatively small.
  • Peristome large with well defined buccal notches.
  • Spines unknown.
Early Cretaceous (Valanginian); western Europe
Name gender feminine
Hemicidaris patella L. Agassiz, in Agassiz & Desor, 1846, by original designation
Species Included
  • Only the type species
Classification and/or Status

Calycina, Salenioida (stem group)

Monotypic. Subjective junior synonym of
Haime, 1849

Distinguished from the type species of Acrosalenia by the absence of primary tubercles on its most adapical interambulacral plates.  This species has a narrow U-shaped posterior genital plate identical to that in Milnia angularis.

Pomel, A. 1883. Classification méthodique et Genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles 503, Aldolphe Jourdan, Alger, 131 pp.