664 Professor Sedgwick and R. I. Murchison^ Esq , on the 



Slate Rocks of Cornwall. 



Before we proceed to describe the culmiferous series, we must notice the 

 relations of the successive groups of North and South Devon, above described, 

 to the slate rocks of Cornwall. The Plymouth limestone, as before stated, 

 thins out to an edge in Whitesand Bay, being there represented by some in- 

 considerable beds of red calcareous sandstone and calcareous slate, with frag- 

 ments of encrinital stems, and a few other organic remains. Nor does it 

 again appear on the south side of Cornwall ; being apparently cut off by the 

 trending of the coast to the north-west of its line of strike. But the lower 

 division of the fossiliferous slates of South Devon does pass into Cornwall, and 

 gradually deflecting to the south-west, ranges through the cliffs at the mouth 

 of the Looe River, through the hills near Talland, and thence by the hill above 

 Lantivet Bay to the mouth of the Powey river. The same calcareous slates 

 reappear on the other side of the river, and are traced continuously through 

 Greber Head, the south-eastern promontory of St. Austell Bay. 



At all the above-named places fossils are abundant, though generally in the 

 form of casts, and sometimes much obscured by cleavage. From the beds near 

 Fowey we obtained several specimens of a large, deeply-ribbed spirifer, casts 

 apparently of terebratuls, stems of encrinites, and several fragments of corals. 

 The same calcareous slates, sometimes passing into impure limestone, reap- 

 pear near Veryan, and thence descend into the cliff" towards the north end of 

 Gerran's Bay — the last place where we found any traces of organic remains 

 on the south coast. 



At Gerran's Bay the strike deviates so much towards the south, that none of 

 the calcareous slates pass through the cliff's that extend to St. Anthony's Head. 

 In their further range, they again undergo a considerable flexure towards the 

 west, which brings them nearly to the mouth of the Helford river ; from 

 which they strike, on the north side of the great plateau of serpentine, to the 

 opposite coast of the Lizard district. 



After what we had seen in South Devon, we were not surprised at disco- 

 vering occasional traces of fossils along the lines above indicated. We were, 

 however, astonished at the extraordinary number of organic remains in some 

 parts of the country hitherto described as not fossiliferous. The calcareous 

 slates are not confined to the line here indicated, but break out, on the eastern 

 side of Cornwall, at considerable distances from the coast*. 



* For example, there is limestone imbedded in slate about half a mile south of Hessenford ; 

 also at Catchfrench, a mile and a half above Hessenford ; and at Coldrenick, a little east of 

 Clicker Tor, &c., &c. 



