\ 

 82 STRATIGKAPHICAL GEOLOGY 



Feet. 



["Sandstones and shales, with Orthis Hieksi .... 100 

 "> -I Flags and shales, with Paradoxidcs Davidis .... 350 



a I Flags and shales, with Paradoxides Hieksi . . 300 



m v 



"^ f Grey flagstones and grits with Paradoxides aurora . . 150 

 ea I Red, purple, and grey sandstones and slates with Paradoxides 



^l solvensis 1500 



2 ^Yellowish sandstones and grey flags vfiih Paradoxides Harknessi 150 



2550 



The lowest beds are yellowish, sandstones with, some pebble beds, 

 and above these are grey flags which have yielded a number of 

 fossils, including Paradoxides Harknessi, Plutonia Sedgwicki, Micro- 

 discus sculptus, Conocoryphe Lyelli, Agnostus cambrensis, and Hyolilhes 

 antiqua. The central group is of great thickness and yields 

 fragments of fossils at different horizons, but it was only near the 

 top that Dr. Hicks found Paradoxides solvensis and Conocoryphe 

 solvensis with some other fossils. The upper beds contain other 

 species of Paradoxides and Conocoryphe, while Agnostus cambrensis 

 and Lingulella ferruginea occur in all three groups. 



The Menevian Group consists mainly of dark-grey flagstones and 

 black shales, and from the middle zone Dr. Hicks obtained 28 

 species of fossils belonging to the Trilobite genera Paradoxides, 

 Conocoryphe, Microdiscus, Anopolenus, Arionellus, Erinnys, Agnostus, 

 and Holocephalina with Brachiopods of the genera Lingulella, 

 Discina, Obolella, and Orthis ; and some Gasteropod Mollusca of the 

 genera Hyolithes, Stenotheca, and Cyrtotheca. 



In Merioneth, according to Messrs. Lapworth and Wilson, the 

 series is represented by the following succession of beds : 



Feet. 



Clogan Beds ( = Menevian), black shales and slates . . . 250 

 Gamlan Shales, a series of grey and greenish shales and flags, with 



beds of grit which thicken eastward ..... 1000 

 Barmouth Grits, thick felspathic grits with some bauds of pebbles 600 

 Hafotty or Manganese Shales, grey and green shales and flags with 



grits which thicken eastward 1000 



About 2850 



No fossils have yet been found in the great series of greenish- 

 grey shales and grits which seem to be the equivalents of the 

 Solva stage, but the Menevian has yielded 19 species, includ- 

 ing 5 species of Agnostus, 2 of Anopolenus, 3 of Paradoxides 

 with Microdiscus punctatus, Lingulella ferruginea, and Hyolithes 

 corrugata. 



In Carnarvonshire the Solva Group is evidently represented 

 by the upper green and purple slates of Llanberis and of Penrhyn 



