Vol. 68.] SUCCESSION IN THE NOKTH-WEST OF ENGLAND. 



505 



6. The abundance of specimens of Cyrtina septosa in the Chonetes-'a.^. 

 comoides Band, which here far outnumber the chief index-fossil of the type- 

 disti'icts. 



6. The evidence of important tectonic disturbances, especially in the eastern 

 portion of the district, by which the beds are so thrust and tilted that the 

 zones are, in places, inverted. 



7. The presence of isolated inliers of limestone among the rocks of the 

 Millstone Grit Series on the southern mai-gin of the district, which exhibit 

 lithological and palaeontological characters unknown at any horizon in the 

 type-districts, and in their faunal and structural peculiarities recall the brec- 

 ciated limestones of the knoll-reef country on the south-east, of which they 

 appear to be fragmentary continuations, brought into their present position by 

 thrusting. 



(1) The Western Portion of the Arnside District. 



AtTiyris-glahristria Zone: the Meathop Outlier. — 

 The lowest beds are exposed on the north side of the Tvent estuar}' 

 at Low Meathop, in a small quarry on the east side of the lane 

 leading down to the farm. The actual junction with the Silurian 

 is not seen, but the latter crops out in a field hard by. The 

 •exposure consists of a few feet of very tough blae limestone, 

 overlain by unfossiliferous earthy shales. The limestone contains 

 one or two layers crowded with the remains of Camarotoeclda 

 proava, associated with the following species : — 



Solenopora, sp. nov. 



■Carcinophyllum, sp. nov. 

 LojpTwphyllum meathopense, sp. nov. 



Athyris glahristria (Phill.). 

 €amarotoechia proava (Phill.). 



Bhijnchotreta angulata (Linn.). A 



large form. 

 Semimda aff. ficoidea (Yaughan). 



Modiola cf. lata Portl. 

 Myalina sp. 



The form of Semimda found here and in the overlying beds east 

 of the road is a large inflated form, difficult to distinguish from 

 S. ficoides (Yaughan) of the Bristol Seminula Zone.^ The 

 association of Solenopora with CamarotoecMa proava and Athyris 

 glahristria in this exposure points clearly to the horizon being that 

 of the C.-proava Band of the Shap-Abbey and Stone-Gill sections 

 already described. 



The Seminula-gregaria Sub-zone is well exposed in a suc- 

 cession of old quarries between the railway and the road to the 

 east of the gas-works ; the total thickness to the top of the eliff is 

 about 140 feet. The beds consist chiefly of compact limestones 

 and dolomites, some of the latter containing up to 30 per cent, of 

 magnesium carbonate. 



The Algal Layer. — The layers near the base of the Meathop 

 section are largely made up of the remains of calcareous algae, which 

 occur on weathered surfaces as grey concretionary spots and nodules 



^ See PI. LI, fig. 6 ; also A. Yaughan, Proc. Bristol Nat. See. n. s. vol. x 

 .(1903) p. 122. 



