Introduction 82

Leslie Bairstow 82

Biography 82

Bairstow's unpublished work 84

Geological maps 84

Geological structure of Robin Hood's Bay 93

Stratigraphical succession 93

Bed numbers 95

Detailed succession in Robin Hood's Bay 96

Lithostratigraphy 111

Staithes Sandstone Formation 111

Redcar Mudstone Formation 111

Exposures in Robin Hood's Bay now 114

Correlation with previous descriptions 114

Bairstow's ammonite collection 115

Systematic description of the ammonites and nautiloids 118

Family Juraphyllitidae 118

Family Lytoceratidae 118

Family Psiloceratidae 119

Family Schlotheimidae 119

Family Arietitidae 119

Subfamily Arietitinae 119

Subfamily Agassiceratinae 123

Subfamily Asteroceratinae 123

Family Echioceratidae 125

Family Oxynoticeratidae 129

Family Cymbitidae 132

Family Eoderoceratidae 132

Family Coeloceratidae 136

Family Phricodoceratidae 137

Family Polymorphitidae 137

Family Liparoceratidae 141

Family Nautilidae 144

Biostratigraphy 144

Acknowledgements 150

References 150

Rocks of Lower Liassic (Sinemurian and Lower Pliensbachian) age exposed in Robin Hood's Bay, near Whitby, north Yorkshire, are described from the mapping, stratigraphical descriptions and ammonite collections made by Mr Leslie Bairstow in the years 1927–1970, and preserved in the Palaeontology Department, The Natural History Museum, London. His large-scale map of the geology of the foreshore is published on five sheets at a scale of approximately 1:5000. The stratigraphical sequence from bed 418 at the base up to bed 600.5 at the top of the Lower Pliensbachian is 163.74 m thick, and consists of the Redcar Mudstone Formation, for which four members are formally defined – the Calcareous Shale (at the base), Siliceous Shale, Pyritous Shale and Ironstone Shale Members – overlain by the lower part of the Staithes Sandstone Formation. The lowest beds exposed by the lowest spring tides are Sauzeanum Subzone, Semicostatum Zone, in age; ammonites occur in all subzones, and the only uncertain boundary is that between the Masseanum and Valdani Subzones (Ibex Zone), where there are few characteristic ammonites. Bairstow's ammonite collection consists of more than 2360 specimens, all from recorded horizons, and is notably rich in Promicroceras, Asteroceras, Eparietites and Oxynoticeras from the Obtusum and Oxynotum Zones, Echioceratids, Eoderoceras and Apoderoceras from the Oxynotum, Raricostatum and Jamesoni Zones, and Liparoceratids from the Davoei Zone, making it a primary source for Sinemurian and Lower Pliensbachian ammonite biostratigraphy. The recently proposed selection of Wine Haven at the south-eastern end of the bay as the Global Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (ie. the world standard definition), is supported by the sequence of ammonites across the Sinemurian/Pliensbachian boundary. All previously figured ammonites from Robin Hood's Bay are listed in a systematic section that includes the evidence on which the ammonite identifications in the paper are based, and 56 of the best preserved ammonites are figured. Eparietites bairstowi sp. nov. is proposed for an early species of Eparietites and a Sowerby Collection ammonite from the Aplanatum Subzone, Raricostatum Zone, in the bay, is designated neotype of Eoderoceras armatum (J. Sowerby).