Five Lower Albian (Lower Cretaceous) areoligeracean dinoflagellate cyst species are present in the Carstone Formation at Middlegate Quarry, North Lincolnshire, UK; Canninginopsis monile , Circulodinium deflandrei, Cyclonephelium compactum, Cyclonephelium intonsum and Cyclonephelium longispinatum . The taxonomy of Circulodinium deflandrei is reviewed with respect to 20 measured Carstone specimens. The taxonomy of Cyclonephelium longispinatum is reviewed with respect to 70 measured Carstone specimens, and a study of 40 measured specimens from its type material in Site 361, Deep Sea Drilling Project Leg 40, offshore south-western Africa. Circulodinium deflandrei and Cyclonephelium longispinatum have recently been considered by other workers to be junior synonyms, respectively of Circulodinium hirtellum and Tenua anaphrissa . However, following detailed study of their morphologies, the synonymies are formally rejected here. An emended diagnosis is given for C. longispinatum . A re-assessment of stratigraphical ranges of taxa co-occurring with the type material of C. longispinatum is consistent with a Late Albian to Early Turonian age range in Site 361.