Article: Two new subspecies of Phacops rana [Trilobita] from the Middle Devonian of North-West Africa

Phacops rana africanus subsp. nov. and P. rana tindoufensis subsp. nov. are described from the Middle Devonian of North-West Africa. They are considered to be close to P. rana milleri Stewart and P.rana crassituberculata Stumm of North America. An origin for P. rana in the European and North African P. schloteimi (s.l.) group is postulated. Migration of forms between the two areas is necessary to explain the distribution pattern of P. rana, and routes between North-West Africa and North America are examined with reference to the contemporary positions of the continents.