30 MONOGRAPH OF DURA DEN. 



rocks which constitute the fish epoch, and of which the Old 

 E,e*d sandstone forms the true distinguishing type. 



The yellow sandstone reappears in the western districts of 

 Scotland, at Kilbarchan in Renfrew, at Girvan in Ayrshire, 

 and, across the Channel, in Ireland, at Cultra in Down, and at 

 Ballinascreen in Derry, The deposit maintains throughout the 

 same relative position to the underlying red and superincumbent 

 strata of the coal-field. It is marked by the same mineralogical 

 peculiarities of structure, and distinguished by similar organic 

 remains. Hence, like all the great leading Scottish formations, 

 it extends persistently across the island, concealed in the more 

 central localities by the traps and carboniferous sandstones, but 

 everywhere maintaining its deep saffron tinge and variegated 

 mottled bands of red shales and concretionary marls. Pterich- 

 thys mapr is abundant in the upper Old Red of the " Heads 

 of Ayr ;" and Holoptychius nohilissimus abounds, along with 

 Cyclopteris Hibernicus, in Prestonhaugh quarry, near Dunse. 



The deposit, along the tract now indicated, may be esti- 

 mated at four to five hundred feet in thickness, and varies 

 from half a mile to a mile in average breadth. The inclination 

 of the beds is various. Korth of Cupar, as seen in the Lady- 

 burn, the dip is about an angle of 20^ ; at Cuparmuir quarry 

 and at Hospital-mill it is at an angle of 16°; while in Dura 

 Den, Drumdryan, Glenvale, and other localities to the west- 

 ward on the farm of Lappa, the inclination is generally from 

 10° to 6°. The rise, or outcrop of the strata, is towards the 

 north, on the slope of the Ochils, and the dip to the south- 

 east. From Cults-hill westwards to the base of the East 

 Lomond, the strata have been thrown down several hundred 

 feet by a series of faults which occur there ; from this point 

 they are again elevated, when the yellow sandstone may be 

 observed along the northern escarpment of the Lomonds, 

 reposing upon the red beds of Drumdreel and Urquhart, 

 where they are cut and abraded into large tabular masses, and 

 grooved in many places by glacial action. 



