The Echinoid Directory

• Test small, low, elongate and depressed, with thin margin and concave undersurface.
• Apical system tetrabasal; central, with four gonopores.
• Ambulacra non-petaloid and narrow; pore-pairs hardly differentiated aborally.
• Periproct supramarginal in deep, broadly triangular groove that extends to the posterior.
• Peristome opening small, subcircular; subcentral to anterior.
• Bourrelets developed as low inflated nodes; vertically sided entrance to peristome. Basicoronal plate longitudinal.
• Phyllodes broadening adorally, with pore pairs in two series, plus one or two distal pore-pairs forming incipient inner series; all pores below petals double.
• No buccal pores.
• Sphaeridia in two rows in each ambulacrum.
• Tubercles on adoral surface large, with bosses eccentric anteriorly in large scrobicules.
• Naked granular area in interambulacrum 5, ambulacrum III.

Cretaceous (Albian-Cenomanian), south-west England.

Nucleolites morrisii Forbes, 1849, p. 8, by subsequent designation Kier, 1962, p. 170.

• O. morrisii (Forbes, 1849); Albian-Cenomanian, UK.
• O. pauli Smith & Wright 2000; Cenomanian, UK.

Irregularia; Cassiduloida; ?stem group Faujasiidae.

Pomel (1883) included in Ochetus, Nucleolites lacunosus, morisii, bourgeoisianus and "probably" similis and collegni. The diagnostic characters of morisii are not shared by any of the other included species nor, indeed, by any specimens figured as morisii by Pomel\'s time. The longitudinally elongate basicoronal plates which project outwards are seen in just two groups, the pygurids and the Faujasiidae. Faujasiidae can have a very similar periproct and anal sulcus, but all have single pores in their ambulacra beneath the petals, and their petals are generally rather well developed and lanceolate. Pygurids have an inframarginal periproct that is flush.

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.

A. B. Smith & C. W. Wright. 2000. British Cretaceous echinoids. Part 5, Cassiduloida. Monograph of the Palaeontographical Society, pp. 391-439, pls 130-138.