James Neihon — Old Red and Carboniferous of Arran. 223 



which has apparently entirely exhausted the red matter from the 

 clay in which it lies, leaving the clay of a creamy white colour. 



Returning now to the question of marine limestones — If they 

 belonged to the Old Red Sandstone age, one would have expected the 

 fauna to be of Devonian rather than of Carboniferous type ; and it 

 would indeed be strange if there should exist at the same time in the 

 sea, in what is now Devonshire and Arran, two faunas so dissimilar 

 as are the Devonian and Carboniferous, and that changes should 

 occur involving the annihilation of the entire Old Red Sandstone and 

 Devonian fauna, and yet leave these Carboniferous fossils unchanged 

 throughout all the long period represented by the Upper members of 

 the Old Red Sandstone, 1 and the whole of the Calciferous Sandstone 

 period to be again inti-odueed unaltered into the British area at the 

 beginning of the Carboniferous Limestone period. It may be so, but 

 I cannot accept it without proof. On the contrary, the fossils show 

 undoubtedly that these are the true Carboniferous Limestone strata 

 themselves. Dr. Bryce (p. 224) records some 36 species of marine 

 fossils from these beds, all of which are found elsewhere in the 

 Carhoniferous series of the West of Scotland. The thing that strikes 

 one most in the limestones at Corrie, Laggan, and Maoldon, is the 

 enormous number of Productus giganteus to be seen. 2 



Now, it will be generally conceded that species, like individuals, 

 have first a period of infancy, and then a full development, from, 

 which they dwindle and gradually die. Productus giganteus is no 

 exception to this rule, and its period of overwhelming development 

 is well known in the West of Scotland near the bottom of the Lime- 

 stone series, where some of the beds are known as Productus 

 giganteus limestone. 



This series of beds is the thickest of the lowest limestones, and 

 is generally called the main limestone ; they have been extensively 

 worked at Beith, Dairy, Busby, Hurlet, Campsie, Carluke, etc., and 

 I have no hesitation in setting down the Corrie limestones as the 

 equivalents of this series of beds, to whose position they correspond 

 stratigraphically. It was my intention to re-examine the shore south 

 of Brodick Bay, in order to have worked out the evidence in that 

 direction, but the broken state of the weather prevented me from 

 completing this part. I may, however, say that the evidence here is 

 not so complete, nor so continuous; while the greater part, if not 

 the whole, of the strata between those already described and the 



1 [The author should hear iu mind that many authorities are inclined to group 

 Upper Old Red Sandstone in the Carboniferous system. The "Upper Old Red" of 

 North Wales and the so-called " Old Red " of the Lake District are now grouped as 

 Basement Carboniferous. The uppermost Devonian beds have a Carboniferous 

 fauna. With regard to the Arran limestones, however, Sir A. Geikie has himself 

 corrected the error. See sequel to this paper, p. 227. — Edit. Geol. Mag.] 



2 I measured a square yard in the roof of one of the mines, and counted in it 

 48 shells of this species. I also counted in the face of the quarry 21 layers of these 

 shells. These figures show that each layer contained (48 x 4840) over 232,000 shells 

 per acre, and this, multiplied by the number of layers, gives nearly 5,000,000 shells 

 per acre ; a number which, however gigantic, is, I am persuaded, under rather than 

 over the actual fact. 



