81 REPORT— 1869. 



tliiu and vevy irregular. They become very thick in the vrestern portion of this 

 county, and in Coonihola Glen they have their greatest development, being at leas 

 3000 feet in thickness. These giitty beds have been termed " Coomhola Grits." 

 They contain some peculiar fossils, and they have others in common with the Car- 

 boniferous slates. 1 hey are interstratiiied with sljvte bands; and although most 

 extensively developed near the base of the Carboniferous slates, they are merely 

 local members of this series, emanating from conditions somewhat different from 

 those from whence the great mass of the Carboniferous slates have originated. 



Having described generally the arrangement of the rocks of the south of Ireland 

 which represent the Pilton beds, and also the deposits which support them, we 

 have now to refer to North Devon. On the north side of Baggy Point and east- 

 ward thereof, there are hard purple sandstones, possessing many of the features of 

 the Old Red Sandstones of the south of Ii-eland, which immediately underlie the 

 " Yellow Sandstones," and upon these in North Devon are light-coloured beds, 

 which represent the Irish Yellow Sandstones. 



In the neighbourhood of Marwood, reposing on the equivalents of the Yellow 

 Sandstone, are greenish-gi'ey grits, afibrding a group of fossils intimately allied to 

 those contained in the Coomhola gTits ; and among these are plant-remains identical 

 with such as occur near the base of the Carboniferous slates. These have been 

 obtained by the Rev. M. Mules. The mineral nature and the fossil remains place 

 the jMarwood sandstones and the Coomhola grits on the same horizon. 



The fossil plants which occur near the base of the Carboniferous slate, and in 

 the Marwood sandstones, are specifically identical with such as are found at the 

 base of the Carboniferous formation in the north of England. Here Filicites linearis 

 and Sar/enaria Velthcimiana occur, and these are the forms which the base of the 

 Carboniferous slates aflbrd. 



The Pilton rocks succeed the Marwood sandstones, and these Pilton rocks in 

 their mineral nature are intimately allied to the Carboniferous slates. The strata 

 which make up the Pilton group consist of shales and slates, generally of a dark 

 colour, with associated sandstones and gritty beds, and occasional thin bands of 

 limestone full of corals. The fossils of the Pilton rocks are very closely connected 

 with those of the Carboniferous slates. Some forms, however, which occiu- in the 

 Pilton rocks have not yet been recognized in their Irish representatives. 



There are species of I'hacops, Strop/icilosiaj)ro(h(cioi(les,a,nda,{ew other species. 

 But such fossils as are most abundant in the Pilton rocks are those most common 

 in the Carboniferous slates. 



There is an idea prevalent among many English geologists that the Coomhola 

 grits are a series of rocks distinct from, and lying beneath the Carboniferous strata, 

 and this idea has, I believe, given rise to erroneous impressions concerning this 

 series. I have pointed out that this is not the conclusion of the officers of the 

 Irish Geological Sm'vey, and my own observations ha^e led me to results similar 

 to theirs. I hope this Meeting will afford more information concerning the Mar- 

 wood beds and the Pilton rocks, and that we shall have farther evidence which 

 will enable geologists to say whether these strata shall be referred to the Devonian 

 group or to the Carboniferous formation. A baud of pale slates, with a few bivalves, 

 lies between the purple sandstones of Mort Bay and the gTeenish-grey grits of the 

 Marwood series. It is desiralile that farther information should be afforded con- 

 cerning these strata and their fossil contents. 



It appears to me that the boimdary between the Devonian or Old Red Sand- 

 stone and the Carboniferous formation is in the British Isles placed in different 

 horizons. In L'eland tlie Carboniferous slates and interbedded Coomhola grits are 

 referred to the latter, while in this country the equivalents of these ai'e looked upon 

 as appertaining to the Devonian formation. 



Besides tlie ^larwood sandstones and the Pilton rocks, there are other matters of 

 greater interest in connexion vrith the geology of Devonshire. 



TheTriassic strata of this coimtry, in the neighbourhood of Budleigh-Salterton, 

 has within it some peculiar pebble-beds, which have been described by Messrs. 

 Salter and Vicary. These pebble-beds aboimd in fragments containing fossils 

 similar to those which the Silurians of Normandy aUbrd. Recently these Triassic 

 strata have yielded toMr.Wliitaker important pala^ontological evidence, in the form 



