TRANSACTIONS OF THE SECTIONS. 75 



Attenuation of the Carboniferous Limestone. 



1200 1025 607 295 169 



This section shows how the limestone diminishes in thickness with the rise of the 

 Wenlock shale towards the south-east. Between the Ty-nant ravine and Tan-y- 

 Castell it has thinned out 200 feet, and at Fron-y-Cysyllt, four miles from the 

 former place, the attenuation is not less than 900 feet. 



The list of fossils collected by the author contained 77 species. Of these, 58 occur 

 in the Upper Grey Limestone, and only 18 in the Lower Brown Limestone. If the 

 Carboniferous Limestone is simply divided into Upper and Lower Limestone, 38 

 species are peculiar to the two upper subdivisions and 19 to the two lower sub- 

 divisions, 20 species being common to both. However, the species are by no means 

 confined to the subdivisions in which they are found near Llangollen, for they occur 

 at different horizons in other districts. 



Oil the 8owxe and Function of Carbon in the Crust of the Earth. 



By A. S. Mott. 



Note on the Carboniferous Coast-line of North Cornwall. 

 By S. ft. Pattison, F.G.S. 



The portion of coast described extends from near Bude to Boscastle, and belongs 

 to the formation first identified by Professor Sedgwick, in connexion with the 

 diagnosis made at Bideford by him and Sir Roderick Murchison, as Culm, or Lower 

 Coal-measures. Bude lies in or near the centre of this formation. The strata have 

 a general northerly dip, and proceeding southwards down the coast of course lower 

 beds become exposed. The Bude beds contain a thin film of Culm, with associated 

 plant remains in a very fragmentary condition. Professor Morris many years ago, 

 in a note published in the ' Proceedings of the Geological Society of Cornwall,' 

 identified some of these remains as Catamites, Sigillaria, and Asterophijllites. 

 Professor Hull states the number of species in the North Devon beds, of which these 

 are the continuation, at 23, and Mr. Townsend Hall at 26. The Bude beds are con- 

 tinued by foldings and succession downwards ; but on arriving at St. Gennes a 

 system of deep blue schistose sandstones appears, from the base fine of the cliff 

 along the remarkable coast landslip which extends for two miles. From these dark 

 blue beds fragments or nodides containing Goniatites appear on the beach. These 

 Goniatite beds extend from Cam Beak to the Buny Cliff, in the parish of St. 

 Juliott. They are most abundant at the St. -Gennes end of the landslip. Here, at 

 a sandpath descending to the shore, on the beach, are huge fragments of fallen rock, 

 containingvery fine large impressions of plants, especially Sigillaria. Proceeding 

 towards Boscastle, at the gloomy gorge of Pentargin, the soft black shales so 

 characteristic of Boscastle form the bulk of the cliff ; but below them rises a slaty 

 rock, once quarried, and in this are found the usual fragmentary plants of the Bude 

 rocks. This, with the associated soft black beds, is the farewell rock of the Carbo- 

 niferous series ; for at the Summer-house Cliff, on the south side of Boscastle, slates 

 arise under the black shales, which at the summit contain traces of Crinoids, and 

 are the commencement of the Devonian slates which are continued to Tintagel and 

 well known as Devonian. 



* Upper portions have been denuded. t Keposes on the Wenlock Shale. 



\ Base not ascertained with certainty. 



