The Palæozoic rocks of North Devon and West Somerset, presenting so complete a change in stratigraphical sequence and læontological and lithological characters from those forming the Coal-basins of Somerset and South Wales and their environs, have long attracted the attention of geologists. The bibliography of the subject, which has since attained such formidable dimensions andembraces so many stars in the geological firmament, had been swelled by the contributions of early theorists; and ere the term Grauwacke had been obliterated from our text-books, the general succession of the rocks had been so admirably sketched by De la Beche in his Report that, although too little quoted as an authority on the stratigraphy of the subject, prevalent opinion has now endorsed the correctness of the succession given by him ; and that succession, having been endowed with a recognized nomenclature by subsequent observers, now forms the basis for the discussion of a wider correlation tending almost to sweep away the distinguishing epithets which had been locally applied to its divisions.