668 Professor Sedgwick and R. I. Murchison, Esq., on the 



fossiliferous slates on the corresponding parts of the north and south coast. 

 Provisionally, we identify the calcareous slates of New Quay, Padstow, &c., 

 with the calcareous slates of Looe and Fowey. We see no reason whatever 

 for considering one series older than the other ; but for a final determination 

 of the question we must look to a future examination of the fossils. The best 

 fossils we possess from the coast near St. Columb Porth, we owe to the kind- 

 ness of our friend Mr. Carlyon of Mawgan. Among them are Encrinites, two 

 or three species of Orthoceratites, and several species of corals, &c. 



The fossiliferous slates near Tintagel (first noticed many years since by Pro- 

 fessor Buckland and Rev. J. J. Conybeare), cannot perhaps be connected by the 

 direct evidence of sections with any of the preceding calcareous groups. The 

 most remarkable fossil in these slates is a very large broad-ribbed Spirifer; and 

 we found a similar fossil among the highly crystalline laminse of the slates near 

 Lesnewth, in the range of the slaty mass several miles further to the east. 

 Calcareous slates, very nearly on the same line, after doubling (along with a 

 great series of inferior beds) round the granite, are carried by a strike about 

 E.S.E. to the quarries near Trenalt and South Pethervvin. From the very 

 numerous fossils in these quarries (among which are many large broad-ribbed 

 Spirifers,ProductaB, Terebratula, two or three species of Orthoceratites, many 

 corals, Encrinites, &c.,) on the whole, nearly resembling those of the great 

 upper limestone of South Devon ; we should place these calcareous slates in 

 an upper group of the great slaty series : and the conclusion is confirmed by 

 the fact, that a section from South Pethervvin to the granite, in a direction 

 transverse to the strike {i. e. about S.S.W.), exhibits for five or six miles a 

 regular descending series. These calcareous rocks are, in respect to the great 

 overlying culm-trough, exactly in the same position with the calcareous slates 

 of Barnstaple ; but on this fact, considering the ambiguous relations of the 

 base of the culm-measures to the rocks on which they rest, we do not at 

 present build any inference. 



From the preceding details we conclude, that whatever classification be 

 given of the slate rocks of South Devon, must also include all, or nearly all, 

 the slate rocks of Cornwall. They form one continuous system, the several 

 parts of which admit no comparison as to age, except that which is sanctioned 

 by the evidence of sections and fossils. The slates of Cornwall are, on the 

 whole, more crystalline than the slates of South Devon, — a fact, however, on 

 which no classification can be founded, as the upper groups, when near the 

 granite, are as crystalline as the lowest. Again, many of the subordinate 

 beds in Cornwall are as mechanical in structure as the very coarsest beds in 

 South Devon. 



