All the Selachian teeth hitherto obtained from the English. Crags referable to the genus Oxyrhina are much compressed antero-posteriorly, and are thus slender in proportion to their size. They are now commonly regarded as representing a single extinct species, Oxyrhina hastalis of Agassiz, and the same form of dentition is abundant in the Pliocene of Italy, besides occurringinother Tertiary deposits in various parts of the world.inItaly and Belgium, however, these comparatively slender teeth are accompanied by a few others of the same genus of very robust proportions; and some of these have received the names of O. Benedeni, O. gibbosissima, and O. Forestii, while others have been identified with O. crassa and O. quadrans. So far as the present writer can judge, none of these robust teeth are capable of being satisfactorily distinguished from the species O. crassa of Agassiz, originally described from the Miocene of the Rhine Valley; and it is under the last-mentioned name that they are recorded in the British Museum Catalogue.