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. 



