Summary The name Processa canaliculata Leach has been applied to a species other than that to which the holotype belongs. The species P. canaliculata Nouvel & Holthuis non Leach has no valid name; it is re-named P. nouveli, with type material from Monaco. P. nouveli and P. canaliculata have been considered to be conspecific by one recent author. New characters for their separation are described from Irish Sea material. The northern form of P. nouveli differs from the Mediterranean form sufficiently to be placed in a separate subspecies. The name P. nouveli holthuisi is proposed for it, with type material from the Irish Sea. The distribution of the four species and subspecies of Processa known to occur in northern Europe is reviewed.