Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/419

 Sir P. Egerton replied that there was no deficiency of pabulum for any kind of fish in the sea represented by the Lias of Lyme Regis. He also made some remarks on another somewhat similar specimen in his own museum. The plate referred to by Dr. Gunther, he stated, was symmetrical, and not like the lateral plates on the Sturgeon, which are unsymmetrical. He therefore thought it dorsal.

2. On the Tertiary Volcanic Rocks of the British Islands. By Archibald Geikie, Esq., F.R.S., F.G.S., Director of the Geological Survey of Scotland, and Professor of Geology in the University of Edinburgh. — First Paper.

[Plate XIV.]

In the present communication I propose to offer to the Society the first of a series of papers descriptive of those latest of the British volcanic rocks which intersect and overlie our Palaeozoic and Secondary formations, and which, from fossil evidence, are to be regarded as of miocene, or at least of older Tertiary, date. Materials for this purpose have been accumulating with me for some years past. In bringing forward this first instalment of them, I wish to preface the subject with some general introductory remarks regarding the place which the rocks seem to me to hold in British geology, and on the nomenclature which I shall use in describing them. These remarks will be followed by a detailed description of the first of a succession of districts where the characteristic features of the rocks are well displayed. Other typical districts will be described in future memoirs.

General Introduction.

1. Area occupied by the Rocks.

The rocks to which I propose to direct attention cover many hundreds of square miles in the British Islands. They spread over the north-east of Antrim, from Belfast to Loch Foyle, forming there a great plateau or series of plateaux, with an area of fully 1200 square miles and an average thickness of 550 feet. From Ireland the same rocks are prolonged northwards through the Inner Hebrides. They form nearly the whole of the islands of Mull, Rum, Eigg, Canna, and Muck. They cover fully three-fourths of Skye, and extend even as far as the Shiant Isles. But far beyond our own area they reappear with all their characteristic features in the Faroe Islands, and again in the older volcanic tracts of Iceland. In studying the volcanic phenomena which these rocks present to us, therefore, we are not occupied with limited or local features, but with the records of perhaps the most remarkable period in the history of volcanic action in Europe— records which, in spite of the