I. I ntroduction . A mong the geological specimens obtained from Cyrenaica by Prof. J. W. Gregory, during a journey through that province of Northern Africa in the summer of 1908, are a considerable number of molluscan remains, which it has been my privilege to study and report upon in the following notes. It may be at once mentioned that the more important part of this collection will be presented by Prof. Gregory to the Geological Department of the British Museum (Natural History). Speaking generally, the shells are badly preserved, and some consist merely of internal casts; hence only one new species has been made, namely, Æquipecten cyrenaicus , referred to the Priabonian horizon—a more useful purpose, it is hoped, being served in the endeavour to show relationships to already described forms. The specimens are, however, easily divisible into various groups of the Kainozoic System, none offering characters that would indicate their attribution to the Mesozoic or any older series of the sedimentary rocks. The more ancient specimens are the most numerous and probably of greatest importance, since they denote such horizons as the Lutetian, Priabonian, Aquitanian, and Vindobonian: those of later age belonging both to the earlier and to the newer deposits of the post-Pliocene Epoch. The rocks associated with the Lutetian and Priabonian fossils are full of nummulites and occasional specimens of Orthophragmina ; while those that form the matrix of the Aquitanian and Vindobonian specimens exhibit foraminiferal organisms such as Operculina, Amphistegina, Lepidocyclina , etc., but no nummulites. This is interesting confirmation of