On some Fossiliferous Beds in the Silurian Rocks of Wigtownshire and Ayrshire

The difficulty of assigning to the great chain of rocks of the south of Scotland their true place in the geological series, arises from the rarity of fossil remains, and from the want of beds with such well-marked mineral character, as to enable the observer to determine their superposition. Part of this obscurity has been lately removed by Mr. Nicol's description of fossiliferous beds in the valley of the Tweed (Geol. Journ. vol. iv. p. 195); and as any additional information, however scanty, may be interesting, I shall briefly describe the localities in Wigtownshire and the south of Ayrshire where I have found fossils, commencing with some account of the general structure of the country. The description given by Mr. Nicol of the physical structure of Peeblesshire applies in the main to Wigtownshire and the south of Ayrshire. There is the same prevalent strike in an E.N.E. direction, a system of valleys running parallel to the strike formed by the convolutions of the rocks, with another transverse system of valleys at right angles to the former, remarkably equidistant, and through which the principal drainage of the country is effected. The rivers Stincher and Finnart are instances of the former system; the Cree, the Bladenoch and the Tarf, the Luce, and the Piltanton of the latter.