388 Dr. Whrelton Hind 4' Juhn T. Stubbs— 



Upper Black (in part), and possibly some of the cherts equal the 

 U[)per Dibnnoiihyllam zone of Bristol; while the Black Limestone 

 and Shales of Teilia, Holywell, and Baggilt are the homotaxial 

 ecpiivalents of the Pendleside Series. 



Morton classified all the beds which occur between the 

 Carboniferous Limestone and the Coal-measures as Cefn y Fedw 

 Sandstone. He acknowledged, in various writings, bis doubts as to 

 the exact correlation and homotaxial equivalents of the several 

 members of the series. The base and the top of the series 

 unfortunately are very variable from north to south, owing to the 

 peculiar and rapid lithological changes which the upper beds of the 

 Carboniferous Limestone Series undei'go in this direction, and also to 

 the fact that the Pendleside Series overlying the limestone, although 

 1,000 feet thick at Holywell, and the Gwespyr Sandstone Series, 

 300 feet thick, have, if represented near Llangollen, thinned out 

 to a very few feet. Further, Mr. Morton did not recognise that the 

 Posidonomya Becheri Limestones of Teilia and Holywell belonged to 

 the same pal^eontological sei'ies, and classed the latter as Coal- 

 measures, in spite of their fossil contents. 



Morton, however, recognised the important fact that the 

 basement conglomerate did not necessarily indicate the base of the 

 Carboniferous Limestone in any but a very local sense, and 

 that these beds were the true equivalents of beds fairly high in the 

 sequence elsewhere. His carefully detailed work and estimates of 

 thicknesses have lieen of great help to us, and with most of his 

 palteontological work we are in accord. A very serious error was 

 made by Mr. Walker (Proc. Chester Soc. Nat. Sci., p. 9, 1878) in 

 referring to the Holywell shales as the equivalent of the Lower Coal- 

 measures of Lancashire, a mistake unfortunately adopted by the 

 Survey, who state on p. 62 of the Memoir (op. cit. sup.) : — " The 

 Holywell shales, which run through the country and form a 

 convenient base for the Lower Coal-measures, resemble some black 

 sliales, with bands or nodules of argillaceous limestone, which occur 

 in the Lower Coal-measures of Lancashire, and contain a similar 

 fauna, composed chiefly of Posidonomya, Avicidopecteu, Goniatites, 

 Bellerophon, coprolites of fish and plant remains." The absence of 

 specific determinations renders this argument of very little value. 

 Unfortunately for their point of view, Posidtmomya [Becheri) does 

 not occur in the Coal-measures. The Goniatites are Lower Pendleside 

 forms, and the plants are not Coal-measure species. 



Moreover, the Holywell shales are below the Gwespyr Sandstone, 

 which is the equivalent in North Wales of the Millstone Grit. The 

 thickness of this sandstone, about 300 feet, should have opened the 

 e^'es of anyone who knew the Lower Coal-mtasures of Lancashire or 

 the Midlands, where a sandstone at all approaching that thickness is 

 unknown. Moreover, Morton shows that the Gwespyr Sandstone 

 has a nmtrix of decomjiosed felspar similar to the 1st or Roaches 

 Grit of North Staiibrdshire. As far as we know, felspar is not 

 present in this manner in any known Coal-measure sandstone. The 

 nnstakeu conekition ought not to have occurred, on purely 



