Vol. 68.] SUCCESSION TN THE NORTH-WEST OF ENGLAND. 511 



portion of the sub-zone is well exposed in a series of quarries under 

 the Red Hills, where it contains a sparse fauna consisting chiefly 

 of Bellerophons preserved as casts. 



The Nematojpliyllum- minus Sub-zone reaches a thickness 

 of 350 to 400 feet on Arnside Knott, and forms the whole of the 

 Knott above the Red Hills. The lower portion, a compact cream- 

 coloured limestone, is well exposed at Hare Tarrock on the western 

 Hank of the Knott, and is frequently quarried in the district, as at 

 Wharton Crag and Sandside. Productus-eorruciato-liemis]}liericus, 

 Clionetes pajnlionacea, and Seminula amhigua occur in some 

 abundance. The upper portion abounds with specimens of Clionetes 

 2mpilionacea,y^h.\Q\i in places give a hssile character to the bedding- 

 planes. Occasional masses of Nematophyllum minus in the position 

 of growth occur, and these persist to the summit of the Kuott. 

 On the coast the beds are disturbed by small faults and crushes, 

 and in places are much jointed, and stained with hsematite. The 

 general outcrop is shown in the map (PL LIY). The Bryozoa 

 Band has not been recognized in this district. 



The Lower Bihunopliyllum Sub-zone covers a considerable 

 area to the south and east of Silverdale village, the prevalent dip 

 being southwards and south-eastwards ; but east of Silverdale Green 

 the beds turn over to the east, as they approach the disturbance 

 which runs near Silverdale Station. The beds are also well exposed 

 along the coast, between that station and Jenny Brown's Point. 



The Clionetes-^ii. comoides Band crops out at intervals along 

 the shore, and is here specially rich in specimens of Cyrtina septosa ; 

 it is overlain by markedly-brecciated beds containing elongated 

 concretionary structures — the ' Stick Bed,' which is constantly 

 found associated with this band in all the western districts. 



Ko beds that can be definitely assigned to the Upper Dihuno- 

 pliyllum Sub-zone occur in the Silverdale section. West of Jenny 

 Brown's Point the band is brought in again by a small strike-fault; 

 the pseudo-breccia beds here show a more definite brecciateid 

 structure than usual, the fragments being cemented by haematite 

 and calcite. In places, however, the brecciated beds appear to pass 

 laterally into ordinary compact limestones. 



In Middlebarrow Quarry, close to the Purness Railway, an 

 interesting thrust-plane, making a small angle with the bedding 

 and hading nearly due east, has been laid bare by the quarrying 

 operations (PL XLY, fig. 2, facing p. 512). The exposure is 

 unfortunately being rapidly quarried avray : this is much to be 

 regretted, as it is seldom that so clear a demonstration of the 

 effects of a strike-fault is to be seen in the field. 



(2) The Arnside District East of the Purness Railway. 



That portion of the Arnside District which lies east of the 

 Purness Railway presents the same general development as the area 



