Coiled nautiloid cephalopods from the British Silurian

Coiled nautiloid cephalopods from the British Silurian are described and their taxonomy revised. The Order Oncocerida is represented by a single specimen of Oxygonioceras oxynotum. Twelve species from the Order Tarphycerida (within which is here subsumed the Order Barrandeocerida) are described: one of Trocholites, two of Ophioceras, two of Catyrephoceras, three of Lechitrochoceras, one of Peismoceras, two of Systrophoceras, and one of Uranoceras. Their distribution, stratigraphical and geographical, is indicated.