ARRAN. GEOLOGY. SECONDARY STRATA, 373 



Among the uppermost beds of red sandstone, one is 

 to be found of an argillo-calcareous nature, containing 

 fragments of entrochi, sometimes round, and in other 

 cases oval, as if compressed. These do not appear to 

 have been as yet referred to any species in the still 

 imperfect history we possess of fossil organic remains. 

 It is probable that the bed itself belongs to some of 

 the inferior strata of that limestone which occurs in 

 much greater masses at Corry ; its position here being 

 sufficient to justify that conclusion, notwithstanding the 

 obscurity which arises, from the small dimensions of 

 the corresponding strata on the northern side of Scriden, 

 when compared with those to the south of this central 

 and fundamental point. 



The limestone varies in different places, but is commonly 

 of a blueish or smoke-grey colour, presenting generally 

 an even and smooth fracture. In one bed I observed 

 shells of which the general outline and features resembled 

 those large terebratulse wjiich occur at Corry, hereafter to 

 be described; but being unable to detach them, in con- 

 sequence of the solidity of the rock, they could not 

 be identified. In other places it contains fragments and 

 pebbles of quartz, or of quartz and schist together, form- 

 ing a compound limestone conglomerate. In one place 

 it is penetrated by minute veins of red sandstone, pro- 

 duced, it is probable, by the intrusion of loose sand 

 into fissures, during the deposition of the sandstone that 

 lies above it. 



The shales present an infinite variety, not only in 

 colour, but in thickness, and in position with respect 

 to the other strata. At times they are so overcharged 

 with red oxyde of iron that they must be considered 

 as iron stones, and in some places they even contain 

 distinct nodules of red granular or compact hematite. It 

 is a transition of this nature that forms the beds of that 

 substance which has been called columnar argillaceous 

 iron stone. Portions of three of these are to be seen 



