The Bivalvia of the Penarth Group, Triassic–jurassic, of South-West Britain

The bivalves from the Penarth Group, Triassic–Jurassic from south-west Britain are described. The systematics section contains descriptions of 48 species, three are assigned to the subclass Protobranchia, genera Nuculana (Nuculana), Rollieria, and Dacryomya. Twenty-two species are assigned to the subclass Autobranchia, infraclass Pteriomorphia including the genera Modiolus (Cyranus), Septifer (Septifer), Grammatodon (Cosmetodon), Liostrea, Nanogyra, Actinostreon, Rhaetavicula, Cuneigervillia, Halobia, Chlamys (Chlamys), Camptonectes (Gandalfus), Oxytoma (Hypoxytoma), Atreta, Harpax, Terquemia, Placunopsis, Plagiostoma, and Ctenostreon. Twenty-three species are assigned to the infraclass Heteroconchia including the genera Myophoria, Gruenwaldia, Myoconcha (Myoconcha), Pachycardia, Trigonodus, Myophoriopis, Neocrassina (Neocrassina), Cardinia, Tutcheria, Protocardia (Protocardia), Palaeocardita, Isocyprina (Eotrapezium), Mesomiltha, Cercomya (Cercomya), Thracia (Thracia), Pleuromya, Gresslya, Pteromya, Pholadomya (Pholadomya), Arcomya, and Peredmondia gen. nov.