192 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



S ilurian series of the south-west of Ireland to those of the Silurian 

 region of England, and also the relation of the Old Red Sandstone 

 to the Dingle beds, and shown that, as in the north of Scotland, 

 all through the south and centre of Ireland the Old Red is every- 

 where unconformable to the rocks on which it reposes, while it 

 passes up conformably into the Carboniferous series. 



Prof. Geikie has suggested that the Dingle beds or Glengariff 

 grits may represent the Old Red Sandstone of Scotland (loc. cit.). 

 Should this be the case they would be the marine representatives 

 of lacustrine deposits. Both, according to Mr. Hull, are uncon- 

 formable- overlain by Upper Old Red conglomerate and sandstone. 



Mr. Ralph Tate held the view that the Dingle beds are the 

 equivalents of the Tilestones or Passage-beds of England and Wales*, 

 or the lowest Old Red. Prof. Hull endeavours to show that between 

 the Glengariff beds and the succeeding formation, be it what it may, 

 either Old Red Sandstone or Carboniferous, there is a great blank, 

 or, in other words, " unrepresented time." This long period Mr. 

 Hull believes was filled up in the south and south-west of England 

 and in Belgium by the extensive series known as the " Middle " 

 and " Lower Devonian beds," lying between the " Foreland grits 99 

 on the one hand and the " Pickwell-Down Sandstone " on the other. 

 Prof. Hull also believes that " while a deep sea, in which were 

 deposited the Middle and Lower Devonian beds, overspread the 

 south of England and adjoining continental areas, land conditions 

 prevailed in the south of Ireland during the same period." 



The analogy between the 0]d Red Sandstone of the south of Ireland 

 and its supposed representatives in North Devon, Belgium, and 

 Scotland receives critical analysis from Mr. Hull. That author 

 endeavours to demonstrate that the Middle and Lower Devonian 

 rocks of North Devon are totally unrepresented in the Irish area, no 

 correlation being possible above the Eoreland beds. I believe no 

 one who has ever examined the area south of the Pickwell-Down 

 Sandstone can doubt that the Baggy, Marwood, Croyde, Barn- 

 staple, and Pilton beds are upon the same general horizon as the 

 Carboniferous slate and Coomhola grits of Ireland, and that the 

 Pickwell-Down Sandstones represent the Upper Old Red Sandstone 

 of the south of Ireland. Both on physical and palaeontological 

 grounds these two groups seem to agree. Although the freshwater 

 shell Anodonta JiJcesii has not occurred in the Baggy or Pilton series 

 in North Devon, its plant associate, Adiantites(Palaiopteris)liiberniciis 1 

 has been found in the Baggy beds, or immediately above the Pick- 

 well-Down Sandstone (Upper Old Red). I do not despair of finding 

 the Irish shell in North Devon, especially after its occurrence in 

 Northumberland in the lowest Carboniferous rocks of that area. We 

 may well believe that the " lacustrine " conditions of the south of 

 Ireland gave place to marine conditions over the Devonian area 

 during the same time. 



Mr. Hull proposes the following tabulated form as representative 

 for two areas, viz. the south of Ireland and North De^on : — 

 * Weale's series. Geology. Portlock and Tate, p. 72. 



