THE BORROWDALE SERIES AND THE CONISTON FLAGS. 467 



The ruetamorphic limestone of Wastdale Head has above it rocks 

 which also exhibit changes, the effect of the influence of the Wast- 

 dale-Crag granite. These appear in the form of rocks banded white 

 and black with a pseudo-gneissic structure, the black bands beginning 

 to prevail higher up in the series until hard dark-grey strata prevail, 

 having lighter beds associated with them. These light-grey rocks 

 are very compact, showing no traces of lamination, and possessing a 

 conchoidal fracture. They are translucent on the edges, and, but 

 for their colour, would be referred to the Helleflint of the Swedes, 

 or to some form of felstone, were it not for their bedded character, 

 which is very manifest. These rocks are intersected by an Elvan 

 dyke emanating from the granite. This Elvan dyke effervesces with 

 acids, from the presence of carbonate of lime derived from the 

 metamorphic limestone, which has infiltrated itself into the in- 

 terstices of this dike. 



The fossils of the Coniston Limestone are numerous, but usually 

 not well preserved. Sometimes they occur in great numbers, and in 

 a state of good preservation, in the limestone itself, as is the case at 

 Keislej 7 . Usually the limestone is nearly destitute of fossils, and 

 the palaeontologist is obliged to have recourse to the shales associ- 

 ated with the limestone, in which the fossils, though numerous, are 

 greatly distorted by cleavage. "Without quoting here the lists of 

 fossils from the Coniston Limestone given by M'Coy (Palaeozoic 

 Fossils) and by Salter (Cat. Cambr. and Sil. Fossils), we subjoin a 

 list of the more important in our own collections, which have been 

 mostly obtained from the limestone of Keisley, near Dufton. 



Fossils of the Coniston Limestone. 



Actinozoa. 



1. Petraia, sp. Keisley. 



2. Chcetetes, sp. A small dendroid form, such as is usually called Steno- 



jpora fibrosa, var. ramulosa : the surface is unknown ; but it is perhaps 

 referable to Chcetetes Fletcheri, E. & H. Keisley. 



3. Heliolites insterstincta, Linn. Pool Wyke. 



4. Halysites catenularis, Linn. Keisley. 



5. Petraia ceqitisidcata, M'Coy. Millom and Long Sleddale. 



Polyzoa. 



1. Fenestella (?) assimilis, Lonsd. Keisley. 



2. Ptilodictya costellata, M'Coy. Millom. 



3. Ptilodictya, sp. Keisley. 



likewise in the metamorphic Liassic Limestone in the Isle of Skye. In Ireland 

 it is met with among the metamorphic Lower Silurian Limestones of Donegal, 

 at Derrylougharn, Barnes Gap. and elsewhere in that comity. Its occurrence 

 at Wastdale Head is the first instance of this mineral having been found in 

 England. It consists of silicates of lime and alumina, with small portions of 

 oxide of iron and magnesia — a composition very likely to result from metamor- 

 phic action on a limestone such as the Coniston Limestone. 



