British Cretaceous Echinoids

ABSTRACT Part 7 describes the British fauna of Cretaceous irregular echinoids of the order Holasteroida. Holasteroids are heart urchins with a stretched apical disc in which the anterior and posterior genital plates are separated by intercalated ocular plates II and IV. They have either meridosternous or metasternous plastron plating. In the British Cretaceous they first appear in the Aptian and one genus, Pseudholaster, is moderately diverse in the sand facies of the Lower Cretaceous. Generic diversity increases in the chalk facies, where representatives of 12 genera are found. In total 48 species and 14 genera or subgenera are dealt with. Three new genera are established, Protocardiaster, Plesiohemipneustes and Crassiholaster, and eight new species are described, Pseudholaster caseyi, P. depressus, P. blackdownensis, Cardiaster protoplanus, Plesiocorys (Plesiocorys) transiens, P. (P.) basiprocta, Infulaster praecursor and Lampadocorys ennisi.