0^ THE NOETH OF lEELAND. 535 



thickness of those rocks which, in the south of Ireland particularly, 

 is interposed between the quartzose conglomerate and the limestone 

 proper. Such deposits, too, might be expected occasionally to 

 partake of the character of the basal conglomerates, and a rearranged 

 form of these rocks would often be the result, which explains the 

 occurrence of pebbly quartzose beds like those in the "White Water 

 before referred to, and which are almost undistinguishable from the 

 Old Red Sandstone. 



In conclusion, I think it would be very desirable to retain the 

 term Old Red Sandstone as applicable to those rocks included under 

 groups 2 and 3, comprising all those above the unconformability at 

 the top of the Fintona and Dingle beds up to the commencement of 

 strata in which marine forms reappear*. Undoubtedly these beds 

 form the base of the Carboniferous group ; yet on account of their 

 very great difference, both lithologically and palseontologically, I 

 think it necessary that they should be distinguished from them, and 

 indicated by a different symbol and colour on geological maps. The 

 term Carboniferous Sandstone, often given to portions of this group, 

 has been productive of much misunderstanding and confusion, while 

 Old Red Sandstone, if strictly limited as proposed, would have a 

 fixed and definite application. 



^ Professor Hull holds similar views regarding this classification. See his 

 paper on the Carboniferous rocks, Quart, Journ. (^eol. Soc, Nov. 1877, p. 616. 



