Article: New genera and subgenera of Mesozoic Bivalvia

The following new taxa, belonging to the families stated, are diagnosed and discussed: Palmoxytoma subgen. nov., type species, Pecten cygnipes Young & Bird, Middle Lias (Oxytomidae, now advanced from subfamily to family rank); Rhaetavicula gen. nov., type species, Avicula contorta Portlock, Rhaetic (Pteriidae ?); Ornithopecten gen. nov., type species, Aviculopecten bosniae Bittner, Middle Trias (Aviculopectinidae); Ensio gen. nov., type species, Ptychomya agassizii Lycett, Bajocian (Astartidae).