GEOLOGY. 29 



tions, feathering out and in among the sandstones and traps 

 throughout the estuaries of the Tay and Earn, in the Carsc 

 of Gowrie, and over the range of Strathmore to the Hne of the 

 Grampians. 



The yellow sandstone occurs as the next overlying rock in the 

 ascending series, commencing on the western side of Dura Den 

 (m) on the banks of the river Eden, and stretching southwards 

 about a mile to the middle of the ravine, where it abuts 

 against a trap dyke, which separates the Devonian from the 

 Carboniferous strata. On the eastern side, at the entrance to 

 the Den, the rock is wasted away by the action of the waters, 

 which leaves a large open space, where the underlying red 

 member of the series is exposed to view. The deposit occupies 

 the valley of Stratheden, and ranges under the Carboniferous 

 cliffs of Nydie, Blebo, Cults, the Lomonds, Binarty, the Cleish 

 and Saline hills, and in great part of this range the two sys- 

 tems are separated by masses of greenstone trap. At the 

 northern opening of the Den the rock reposes unconformably 

 on the underlying red beds, which are here of identical colour 

 and mineral texture with those of Clashbennie, and character- 

 ized by similar white-stained large scales of the Holoytychius 

 nobilissimus. The lower beds of the Carboniferous series, of 

 great thickness, rise again over the yellow beds towards the 

 southern opening of the ravine, which are likewise uncon- 

 formable, and maintain the same relative unconformable super- 

 position through the entire range, as already described, except 

 where disturbed by the intervention of the igneous rocks. 

 Thus enclosed between these two well-marked and distinctly 

 separated systems, the intermechate lying beds of the yellow 

 deposit of Dura Den present facilities for study which are 

 seldom to be met with, unmistakably define the limits and 

 the relations of their respective systems in the geological 

 calendar, and from their rich and varied fossihferous remains, 

 justly entitled to be classed with that remarkable series of 



