620 EDWAKD HULL ON THE CLASSIFICATION is an additional reason why these formations should be grouped together in one division as here proposed*. Ascending into the overlying flagstones the molluscous forms dis- appear, either owing to migration or because the strata were not favourable to their preservation ; but instead of these we find those remarkable tracks both of annelids and molluscs which are described and figured by Mr. Baily in the publications of the Survey f . That these flagstones and associated grits and shales are the exact equi- valents in time of the Millstone-Grit series of England there can, I think, now be no question since the identification of the succeeding beds with the " Gannister Beds," of the north of England, which are immediately superimposed on the Millstone-Grit series of that district $. Gannister Beds. — The beds overlying " the Elag series " consist of hard grits, shales, dark mudstones, and two or three thin but work- able beds of coal, which have been traced around the entire coal- field, and worked at several places, such as at Modubeagh, Wolf hill, Rushes, Tollerton, Eossmore, and Skehana. The Bilboa coal, with Bellinurus regina, lies above these seams, and is included by Mr. Hardman in the Lower Coal-measures. Like the Gannister coal the second of these seams has a hard floor, " compact and quartzose," while the shale roof of the Wolf hill seam contains shells of the genera Avicidojoecten, Goniatites, and Bellerophon§; along with these are other species, presently to be mentioned, occurring near Castle- comer. Thus in every respect these beds resemble " the Gannister Beds " of England, and, like them, are characterized by a marine fauna. The list of fossils above given has recently been considerably am- plified by the discovery of a slightly calcareous band in the Lower Coal-measures of Castlecomer, just below the rock of the second coal, containing a remarkable assemblage of marine forms. The existence of this band was brought to the notice of Mr. Hardman, of the Geological Survey, about two years since, by Mr. Aher, of Castlecomer, who states that it was laid open in a quarry in beds associated with the Skehana coal |[. The fossils, which are usually small in size, consisting both of those discovered by Mr. Aher and subsequently collected by the officers of the Survey, have been named by Mr. Baily, Acting Palaeontologist to the Survey, as follows : —
- In the S.W. of Ireland (Kerry &c.) the Yoredale Shales apparently overlap
the Upper Limestones and rest on the Lower ; the change of beds is clear and decisive. f 'Explanation" to sheet 128 of the Geological-Survey Maps, p. 14.
That the vthole series from the top of the Limestone into the upper
measures of the coal-field represents the " Millstone Grit and Yoredale Series " of England has been suggested by the late Professor Jukes himself. (See Jukes and Geikie's ' Manual of Geology,' p. 591, as well as in other places.) § Jukes and Kinahan, Explan. sheet 128, p. 13. || The position of the band from which Phillipsuc has been taken is (according to Mr. Hardman) twenty yards above the second or " Skehana Coal." The beds consist of dark bluish shales, underlying a massive and coarse sandstone well known throughout the district.
