But these are not the only fossils, or organic remains, to be found in the clay, slates, &c., of the Silurian system. Passing by those we have briefly indicated above, there are others of a highly interesting character, concerning some of which we proceed to give a brief history. Being in Cornwall a short time since, we made a visit to Polperro, a romantic but out-of-the-way town on the south-west coast, for the purpose of procuring some remains of fossil fish considered characteristic of the Silurian system of Murchison, and which have been recently discovered by Mr. Couch, an eminent local naturalist, in the cliffs east and west of that town. We did not see Mr. Couch, but found our way to a coast-guardsman, also a naturalist, whom we found to be a most skilful bird and fish stuffer, and a ranger for objects of natural history among the surrounding clay-slates and other rocks. William Loughrin’s collection of Cornish curiosities will well repay any traveller going out of the way twenty or thirty miles, and they will find in him a fine specimen of an intelligent and noble class of men. Below we give some specimens from the Polperro slate. No. 1 might be taken for impressions of sea-weed, so remarkably does it resemble the sea-weed thrown up on our beaches; but it is generally conceded that this is merely a crystallization of oxydized matter, such as may often be found in connexion with manganese. [Illustration: No. 1. ] No. 2 is the Bellerophon,[32] a shell which we shall afterwards find in the mountain limestone, but which is rare in connexion with the Silurian rocks. [Illustration: No. 2. BELLEROPHON, a shell which seems to have been abundant. ] [Illustration: No. 3. REMAINS OF VEGETABLE TEXTURE. ] No. 3 we know not how to describe. We are not certain what organic remains these are; so far as we have been able to examine them, they appear to us the remains of succulent vegetables, (?) probably the thick, soft stems of sea-weed, that may once have reposed in quiescence on the mud of which these slates are composed, and afterwards have been crushed by the superposition of mud and shale, until in the course of ages, by upheaval and depression, they have become a second time visitants of our atmosphere, and now expose themselves to our study and speculations. [Illustration: No. 3. (Portion magnified two natural sizes.) ] [Illustration: No. 4. CORALLINE. (Natural size.) ] Here is one more form of life of this ancient period; it is evidently a coralline, which we also procured at Polperro.