The Early Jurassic Bivalvia from the Hettangian and Lower Sinemurian of South-West Britain

Abstract

In Part 1, the early Jurassic bivalves from the Hettangian and Lower Sinemurian stages of south-west Britain are described. Sections on the history of research, stratigraphy, localities, conventions and techniques are included and a new concept of the type population is presented. The systematics section contains descriptions of 6 species assigned to the subclass Palaeotaxodonta including the genera Palaeonucula, Dacryomya, Palaeoneilo, Rollieria and Ryderia and 6 species assigned to the subclass Isofilobranchia including Myoconcha (Myoconcha), Myoconcha (Modiolina), Modiolus (Modiolus), Modiolus (Cyranus) subgen. nov. and Inoperna including I. lilliputensis sp. nov.