27 



assisted the author materially in mapping the neighbourhood of his 

 residence. 



The upper boundary of the Windermere rocks begins on the south- 

 west at the lower point of Witherslack, and is marked by a great 

 fault which crosses the valley between that hill and Whitbarrow, 

 and appears to pass under the mountain limestone of Whitbarrow, 

 then runs north-east through Underbarrow, by the Chapel, to Mount- 

 joy : on the west side of this fault the Windermere rocks form high 

 ridges of hard slaty grits of dark grey colour, with lighter streaks, 

 dipping N.N.W., while on the east side of the fault is a gritty rock 

 of uniform grey colour dipping E.S.E., overlaid with beds containing 

 the fossils of the Ludlow beds. From Mountjoy the line turns to 

 the north-west, and passes round Crook Chapel, which stands on a 

 ridge of the Windermere grits ; at Crook Common it turns to the 

 north-east, and follows that direction to near Borrowdale, where the 

 formation is lost, being completely hidden by the Ludlow rocks, 

 which there rest on the Lower Silurians. Crook Common is thrown 

 into great confusion by the meeting of two lines of elevation, one 

 coinciding with the E.N.E. strike of the Lower Silurian rocks, the 

 other coming up from the S.S.W. through Cartmel Fell. 



At Backbarrow, below Newby Bridge, the upper beds of this 

 series are slaty, with a wavy cleavage dipping N.N.E. 80°, the beds 

 dipping south- east 80° ; these beds contain irregular calcareous 

 nodules in great abundance, and Orthoceras articulatum was found 

 in them. 



Mr. Sharpe refers to his former memoir for the description of the 

 Windermere rocks on the east of the Lune, which extend to Grey- 

 rigg Forest, Whin Fell, and Howgill Fell ; in these Fells are several 

 axes of elevation which require fui'ther examination. 



Ludlow rocks. — These were described in the author's former paper ; 

 the area covered by them is larger than was there stated, their lower 

 boundary being now carried more to the north, and their eastern 

 portion being extended in a sort of trough between the Lower Silu- 

 rian slates of Shap Fell and the Windermere rocks of Whin Fell, 

 crossing Barrowdale between High and Low Bai-rowbridge. 



In the lowest beds of the series in Fawcett Forest were found 

 Leptcena lata and Tiirritella conica, in a slaty rock. The Terebratula 

 navicula is found thinly scattered throughout all the lower part of the 

 formation, and occurs in vast numbers in a bed which forms about 

 the middle of the Ludlow series. Mr. Murchison has told us that 

 this little shell is usually found in such numbers as to form a bed 

 whigh lies above the Aymestry limestone, and it serves to mark the 

 l)lace of that rock where it is wanting : and Mr. J. E. Davis informed 

 the author, that at Stapleton, near Presteign, where there is no 

 Aymestry limestone, this species is found throughout the whole of 

 the Lower Ludlow shales. Mr. Sharpe has made use of this shell 

 in dividing the Upper from the Lower Ludlow rocks in Westmore- 

 land, classing all the beds containing it in the lower series. The 

 bed in which it occurs in greatest abundance was traced through 

 Underbarrow, by Tullithwaite Hall and High Cray, across the west 



