Two structural entities are distinguished--an overridden and an overriding region. The former consists of lower, middle, and upper Devonian geosynclinal sediments, which have similar counterparts in north and central Brittany (Brioverian facies). The overriding region includes the area of the great crush-zone and the Lizard serpentine complex in the south and the Tintagel region in the north. It represents a part of the quartzite core of a great recumbent anticline, whose rocks belong to a facies characteristic of central Europe and which has been carried northward over rocks characterized by Rhineland and north European facies. Serpentine intrusion was contemporaneous with nappe movement; the age of both is thought to be latest Devonian or possibly early Carboniferous.