Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/845

Rh break or evidence of discordance in the succession of the beds; on the contrary, the change is gradual, with intercalations, and the whole series gives evidence of continuity.

In fine, after a careful observation of the sections near Dunquin, we came away fully impressed with views regarding the relations of these beds similar to those expressed by the late. Sir R. Griffith, that the whole series is one and indivisible, and represents the Upper Silurian beds from the base throughout.

I have already stated that the uppermost fossiliferous band in the coast-section at Dunquin might be regarded as occurring in "the Dingle series," as the purple slates which underlie it are precisely similar to those which overlie it, and are supposed to belong to the "Dingle series." Except, however, for the presence in the beds of purple slate of remarkable "fucoidal" markings, it must be admitted that the Dingle beds and Glengariff grits and slates are lamentably destitute of fossil forms. It must be recollected, however, that the strata are not favourable to the preservation of such forms, even supposing they once existed; and we have only to refer to some well- known marine formations of similar composition to feel assured that the absence of fossil forms is no argument against the marine origin of the Dingle beds. For example, it is rarely that any traces of fossils are found in the "Bala and Caradoc" grits and slates, which occupy so large an area of the north-east of Ireland. The fossils which occur are sporadic and local, but hundreds of feet of strata may be examined over many square miles without rewarding the search of the collector.

Another very apposite illustration occurs in the case of the " Morte Slates " of the Devonian series, attaining a thickness of from 3000 to 4000 feet in the Devonshire section, and succeeding the highly fossiliferous beds of the " Ilfraeombe group." These slates are un- fossiliferous ; but it is improbable that they have not, like the beds below them, been deposited in the sea. Many other instances might be cited in support of the view that, notwithstanding the absence of marine fossils, the beds we are considering may really be of marine origin. Before, however, we admit that the Dingle beds are really destitute of fossils, let us consider the evidence offered by the Parkmore-Point Conglomerate.

Amongst the highest beds of the Dingle series there occur some massive conglomerates forming the cliffs at the entrance to Yen try and Dingle harbours, and particularly well laid open at Parkmore Point. The pebbles are large, well rounded, and formed of various kinds of grit, quartz, hornstone, fragments of purple slate (or schist), white ash, vesicular greenstone, and purple fossiliferous limestone, or highly calcareous grit. From some of the pebbles Silurian fossils were determined by Mr. Salter in 1856.