John Aitken. — Grit-rocks of North Wales. 263 



Fig. 6. Haplocrinus granatum, de Koninck, specimen of the natural size seen in 



profile. 

 Fig. 7. The same, greatly enlarged, seen from the same side. 

 Fig. 8. The same, of the natural size, seen from top of the vault or dome. 

 Fig. 9. The same, greatly enlarged, seen in the same position as in Fig. 8. 

 Fig. 10. The same, greatly enlarged, seen from the base of the Calyx. 



[For procuring the necessary copies (printed from the original Plate in Brussels) to 

 illustrate this paper, I am indebted to my friend, Mr. Edward "Wood, of Richmond, 

 and likewise to the kindness of the author of the paper, Prof, de Koninck, of Liege.] 



T 



ni. — The Grit-kooks of the Eastern Border of North Wales. 

 By John Aitken, F.G.S. 



HE sandstone beds -which skirt the eastern border of Wales, and 

 _L stretch from a little south-west of the town of Oswestry to near 

 the Point of Ayr, on the shores of the Irish Sea, a distance of up- 

 wards of 40 miles in a direct line, have for several years past been a 

 source of perplexity to those who have investigated their peculi- 

 arities, and who have been interested in arriving at a determination 

 of their true age and geological horizon. 



Notwithstanding the difficulties which surrounded them they have 

 been considered by the G-eological Survey, and also by amateur 

 geologists generally, as equivalents of the Millstone-grit formation 

 of the Penine chain. This classification was doubtless adopted from 

 the fact that, in the southern part of the district, in the tract lying 

 between Oswestry and Llangollen, this group of beds is principally 

 made up of sandstones, whilst further north, in the neighbourhood of 

 Mold, the arenaceous character, although considerably modified by 

 the intercalation of calcareous and argillaceo- calcareous layers, still 

 forms a prominent feature ; and also from the further fact of their 

 being situated immediately subjacent to the Coal-measures. 



Having recently had an opportunity of examining this group of 

 rocks, at various parts of its extent, in the southern portion, under 

 the able guidance of Mr. D. C. Davies, of Oswestry, and in the Mold 

 district, in company with Mr. G. H. Morton, F.G.S., of Liverpool ; 

 and having subsequently instituted some comparisons between them 

 and the Millstone-grits of Lancashire and Yorkshire, with which I 

 have had some acquaintance for several years past, and also with the 

 Yoredale series, which I have examined at various places, the con- 

 viction has forced itself upon me, that the classification usually 

 adopted with respect to these sandstones cannot be satisfactorily 

 maintained, whether viewed in relation to their lithological character, 

 strategraphical position, or to their contained fossils, but that their 

 general characteristics have much more of the Yoredale type than of 

 the Millstone-grit ; I nevertheless feel considerable diffidence in 

 placing myself in opposition to the authorities who have written on 

 this subject, and particularly in dissenting from the conclusions of 

 Mr. D, C. Davies, who has had extensive opportunities of studying 

 this series of beds, and who has recently given expression to his 

 views respecting them in the pages of the Geological Magazine.^ 



' The MiUst(Jne-Grits of the North "Wales Border, by D. C. Davies, of Oswestry. 

 Vol. vii., pp. 68 and 122. 



