New FossiUferous Horizon in the Lake- district. 343 



xxxii. pp. 17 and 24). This gifted observer considered the Drygill 

 Beds as being referable to the Skiddaw Slates. He was, in fact, of 

 opinion that we had. here an instance of a passage between the 

 Skiddaw Slates and the Volcanic Series, by the intercalation of the 

 highest portion of the former with the base of the latter in alternat- 

 ing succession — a phenomenon of which he believed he had found 

 instances in other localities in the Lake-district. It is certain, how- 

 ever, that, as regards the rocks here in question, this conclusion 

 could not have been arrived at by a geologist of such experience 

 except under the influence of a preconceived theory. Lithologically, 

 the Drygill Shales do not at all resemble any members of the 

 Skiddaw Series, and they do not precisely resemble any rocks which 

 are known to us as occurring in the Lake-district. They are of 

 the nature of mudstones, with a rough cleavage ; and. of all the 

 Ordovician rocks of the North of England, it is, perhaps, the 

 "Dufton Shales" which they most nearly resemble. Some of the 

 beds are also very like parts of the " Skelgill Series." Apart, 

 however, from the comparatively unimportant character of their 

 lithological nature, the Drygill Shales swarm with fossils — of few 

 species certainly, but of great abundance as individuals — which leave 

 no doubt at all as to their general position in the Ordovician Series. 

 The presence in abundance of such fossils as OrtJiis testudinaria, 

 Dalm., Lejptcena sericea, Sow., and Calymene cambrensis, Salt., Ampyx 

 rostratus, Sars., and Stygina Murcliisonics, Murch., renders it certain 

 that the Drygill Shales are of Llandeilo-Bala age. Upon the whole, 

 the general characters of the fossils would lead us to refer the 

 Drygill Shales to about the horizon of the Llandeilo Limestone, or 

 to a slightly higher point in the series. 



As regards the Lake-district succession, the palaeontological 

 evidence renders it absolutely certain that the Drygill Shales are 

 younger than the Upper Skiddaw Slates and older than the Coniston 

 Limestone proper. They agree most nearly with the "Dufton 

 Shales "as regards their fauna, but they differ from these in the 

 predominance of Ortliides of the type of 0. testudinaria, Dalm., and 

 in various other points. On the other hand, it is not at present 

 possible to decide positively as to the relations which the Drygill 

 Shales bear to the Volcanic Series. From their general position 

 between the Skiddaw Slates on the one hand and the lavas and 

 ashes ("Eycott Series") of the Caldbeck Fells on the other hand, 

 we should be led to conclude that they occupy a place low down 

 in the latter series. It is quite certain that they do not belong to 

 any part of the Skiddaw Series ; and there is, in fact, no evidence 

 that the series of the Upper Skiddaw Slates is present at all in this 

 particular area. On the contrary, the Skiddaw Slates of the Caldew 

 Valley appear to be faulted down against the igneous rocks to the 

 north of them, and it is probable that the Upper Skiddaws are thus 

 completely cut out. Again, the Drygill Shales are lithologically 

 and palEeontologically distinct from any of the fossiliferous rocks 

 which can clearly be shown to lie above the Volcanic Series. It 

 would thus seem almost certain that, though their present position 



