Pomel erected this genus on the basis that the anterior ambulacrum of C. costatus (not C. costulatus as written by Mortensen (1948, p. 323) could not differentiated from the paired ambulacra, with all ambulacra lying in deep furrows. Lambert & Thiery (1909-1925, p. 359) state that Pomel\'s observation that the frontal ambulacrum should be like the paired ambulacra must be erroneous, however, they do not state whether they have reexamined the type specimen. Lambert & Thiery (1909-1925, p. 359) also report that the depression of the ambulacra is not worthy of generic distinction. Kier (1962, p. 225) agrees with Lambert & Thiery (1909-1925) and states that Pomel\'s Passalaster is probably a synonym of Claviaster as he based his species (C. costatus) on a specimen that Cotteau referred to C. coronatus. The Turonian age needs confirmation.
P. M. Kier. 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections, 144 (3) 262 pp.
J. Lambert & P. Thiery. 1909-1925. Essai de nomenclature raisonnee des echinides. Libraire Septime Ferriere, Chaumont, 607 pp., 15 pls.
T. Mortensen. 1948. A monograph of the Echinoidea: 4 (1): Holectypoida, Cassiduloida. Reitzel, Copenhagen, 363 pp., 14 pls.
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, 131 pp. Aldolphe Jourdan, Alger.
