874 J. E. MAER 02s T LIEE-ZONES OE THE 



district with others from the district east of the river Lune, it will be 

 seen that they agree remarkably in lithological character, whereas 

 they are totally different from any shales developed in the Coniston 

 Limestone itself ; and in specimens from Ashgill the same texture is 

 observable, the only difference being that here the beds are much 

 more strongly cleaved. These beds may be described as consisting 

 of leaden-blue calcareous mudstone, of very fine texture, interbedded 

 in places with pale green mudstones, the whole being affected by 

 cleavage, so as to break up into prismatic fragments, which last 

 peculiarity is very characteristic of the beds. They bear in places 

 some resemblance to the lower division of the Coniston Flags, from 

 which they may be distinguished generally by the total absence of 

 the fine lamination so characteristic of the Coniston Elags. 



On the east side of the Lune they are well seen in Spengill, Taiths 

 Gill, Fairy Gill, &o. They are here of considerable thickness, and 

 fossils are fairly abundant, especially Strophomenos, one of which, 

 Strophomena siluriana, Dav., occurs in great abundance in every 

 locality where these beds are found, and has never been found in 

 the underlying Coniston Limestone. Phacops apiculatus, occurring 

 at Rother Bridge, is also characteristic of these beds. The beds 

 here, as in other places, rest immediately and quite conformably 

 upon the Coniston Limestone. 



On following the beds from Shap along the line of strike, the Co- 

 niston Limestone is overlain for some distance by beds referred by us 

 to the Silurian, the Ashgill Shales being absent until we reach Apple- 

 thwaite Common, on the east side of Troutbeck. Here they appear, 

 although extremely thin ; but they possess all the characters of the 

 beds in the district to the east of the Lune, except that they are 

 much more highly fossiliferous. They are again met with on the 

 west side of the great fault which runs down the Troutbeck valley, 

 and may be traced across Scot Beck and Nanny Lane to the well- 

 known section at Skelgill, becoming thicker in passing westward 

 from Troutbeck to this place. The most abundant fossil is Stropho- 

 mena siluriana, and at Nanny Lane and Skelgill several specimens 

 of Phacops mucronatus, var., and Phacops apiculatus have occurred. 

 The beds are next exposed in Pull Beck, on the west side of Win- 

 dermere. At Ashgill, about three miles S.W. of Coniston, we find 

 them magnificently exposed in a quarry and stream, in the former 

 of which they have been worked for flags. They are here very 

 thick, strongly cleaved, and fairly fossiliferous. They still contain 

 Strophomena siluriana in abundance, though Orthis protensa is the 

 predominant form, and Phacops mucronatus, var., and Phacops 

 apiculatus also abound in places. The Ashgill beds are again found 

 at Rebecca-Hill quarry, about three miles north of Dalton-in-Eurness, 

 where they possess the same lithological character and have the 

 same fossils as at Windermere &c. These beds may be traced across 

 the country, and distinguished from the Coniston Limestone by 

 lithological characters only. 



The following list of fossils will further indicate the palaeonto- 

 logical differences : — 



