The Echinoid Directory

• Test subglobular to hemispherical, flattened beneath, domed above.
• Apical disc small, about one-third test diameter; plating dicyclic or hemicyclic. Genital plates large, hexagonal, G2 generally the largest; without tubercles. Periproct ovate, plating unknown.
• Ambulacra narrow and sinuous aborally; plating simple from the ambitus adapically, with small marginal tubercle (imperforate and non-crenulate) on each element; perradial zone narrow with only a single column of granules per plate. Sharp change at ambitus to plates with large primary tubercle; plating trigeminate at ambitus and adorally. Compounded in diadematid style, with all elements extending to perradius. Pore-pairs uniserial above and at ambitus, expanded adorally to form short phyllodes.
• Interambulacral plates about as wide as tall, dominated by a large primary tubercle. Narrow band of small secondaries and granules only peripherally. Adapical most plates with largest mamelon.
• Primary tubercles perforate and crenulate. Those of the ambulacra much smaller than those of the interambulacra.
• Peristome large, more or less flush, with very feeble buccal notches with slight lip.
• No sphaeridial pits and no basicoronal plate.
• Spines massive, clavate, generally with a rather smooth shaft.
• Lantern unknown.

Lower Jurassic (Pliensbachian) - Cretaceous (Aptian, ?Cenomanian), Europe, North Africa, Arabian Peninsula.

Hemicidaris thurmanni Agassiz, 1840, p. 52, by subsequent designation of Etallon, 1862, p. 333.  Etallon states "on peut considerer commes types de ce genre les Hemicidaris alpina Ag. (non Wright) et Thurmanni Ag. ".  Since H. alpina was not a syngenotype, this fixes H, thurmanni as lectotype.

• P. thurmanni (Agassiz, 1840); Oxfordian, Europe.
• P. acinum Desor, 1856; Valanginian, Switzerland.
• P. alpina (Agassiz, 1840); Kimmeridgian, Europe.
• P. clunifera (Agassiz, 1840); Barremian, Aptian, Europe.
• P. collignoni Lambert, ; Bathonian-Callovian, East Africa, Madagascar.
• P. durandi (Peron & Gauthier, 188*; Kimmeridgian, Algeria.
• P. lusitanica de Loriol, 1876; Oxfordian, Portugal, Morocco.
• P. mammosa (Agassiz, 1840); Oxfordian, Europe.
• P. raratuberculata Kier, 1972; Callovian, Saudi Arabia.
• P. depressa Kier, 1972; Bathonian, Saudi Arabia.
• P. romani Kier, 1972; Callovian, Saudi Arabia.
• maybe others

Carinacea, Hemicidaridae, Pseudocidarinae.

Distinguishable from the closely similar Cidaropsis by its weakly crenulate and perforate ambital and adoral tubercles.

Étallon, M. 1859. Études paléontologiques sur le Haut Jura. Rayonnés du Corallien. Mémoires de la Société d’Émulation de Doubs, (3) 6, 53-260.

Étallon, M. 1862. Mem. Soc. helvet. 19, p. 333.

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.