876 J. E. MAKE ON LIFE-ZONES OE THE 



knowledge, to ascertain with certainty to which this appearance is 

 due, but there are some facts which point to unconformity. As we 

 go from Troutbeck eastward, w 7 e find the Ashgill Shales rapidly thin 

 out and disappear before reaching Kentmere. In Long Sleddale the 

 Coniston Limestone itself is thin (leaving out of consideration the 

 contemporaneous flows), and advancing towards Shap, disappears 

 altogether. A fault is drawn by the Geological Survey to account 

 for this ; but it is impossible to say whether this is the case, or 

 whether the whole of the limestone may not have been denuded, and 

 the Silurian rocks deposited directly on the green slates. 



Again, passing from Ashgill to Coniston, on reaching Torver 

 Beck, about one mile N.E. of Ashgill, we find very little room 

 for the Ashgill shales between the Coniston Limestone and the 

 top of the Graptolitic mudstones. Unfortunately the section in 

 this stream is interrupted ; but as the swampy ground which occurs 

 between the limestone and pale shales keeps the same position from 

 Torver Beck nearly to Coniston Waterhead, we can hardly suppose 

 it to be a line of fault, but merely a feature caused by the soft mud- 

 stones. If this be the case, the comparatively great thickness of 

 shales represented in the Ashgill quarry has, in the space of about a 

 mile, nearly or quite disappeared ; this could scarcely be the result 

 of overlap, but points to an unconformity. 



The Ashgill shales are included in the Coniston-Limestone series 

 of Mr. Aveline, which are considered by him to be covered uncon- 

 formably by the Stockdale shales (see Geol. Mag. vol. ix. (1872), 

 p. 441, and dec. ii. vol. iii. (1876) p. 282). 



3. Basement-bed of the Silurian. 



The position of the physical break between the Ashgill shales and 

 the series above is marked in different localities by a bed partly 

 composed of derived fragments, but differing much in lithological 

 character. As Prof. Hughes has worked out these beds in detail, I 

 merely give a list of fossils found in them. 



Fossils of the Basement-bed. 



Actinozoa. 



Favosites Horton, in Eibblesdale. 



JF. fibrosus Spengill; Taith'a Gill. 



Crustacea. 

 Illsenus? Skelgill. 



Annelida. 

 Cornulites Spengill. 



Mollusca. 



Stropbomena siluriana, Dav Spengill. 



S. (sp. with fine strise) Skelgill. 



Meristella crassa Spengill. 



Orthis Taith's Gill ; Skelgill. 



