Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/553

Rh The metamorphic limestone of Wastdale Head has above it rocks which also exhibit changes, the effect of the influence of the Wastdale-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 interstices 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 Keisley. Usually the limestone is nearly destitute of fossils, and the palæontologist is obliged to have recourse to the shales associated 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 (Palæozoic 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.

1. Petraia, sp. Keisley.

2. Chætetes, sp. A small dendroid form, such as is usually called Stenopora fibrosa, var. ramulosa: the surface is unknown; but it is perhaps referable to Chætetes Fletcheri, E. & H. Keisley.

3. Heliolites insterstincta, Linn. Pool Wyke.

4. Halysites catenularis, Linn. Keisley.

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

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

2. Ptilodictya costellata, M'Coy. Millom.

3. Ptilodictya, sp. Keisley.