52 REPORT — 1842. 



logue of all the fossils yet discovered in each of the subdivisions of the Irish moun- 

 tain limestone series, in the strata of North Devon, and in the mountain limestone 

 of Great Britain, arranged in parallel columns for the purpose of comparison ; the 

 notice was also illustrated by coloured sections. 



Mr. Griffith stated that his object in this communication was to prove, by the evi- 

 dence of fossils, that the lower members of the mountain series of Ireland, as arranged 

 by him, really belonged to that series, and not to the old red sandstone, as advocated 

 by some geologists. He described this series as containing two great bands of lime- 

 stone, which he had denominated the upper and lower limestones ; interposed between 

 these limestones were beds of shale, argillaceous limestone and sandstone, forming a 

 series of great thickness, known by the name oi calp) or calp slate. Beneath the lower 

 limestone was a second series of schistose beds, to which he had given the name car- 

 boniferous slate ; under the slate was a series of sandstone beds, frequently interca- 

 lated with slate or shale, and occasionally with limestone; he had denominated this 

 deposit the yellow sandstone; its lower beds rested conformably on the old red sand- 

 stone. Mr. Griffith stated, that those beds varied in thickness at different localities, 

 but that the relative position of each member of the series was always the same; 

 the upper and lower limestones were generally more persistent than the other mem- 

 bers of the series. In some localities the carboniferous slate and yellow sandstone 

 were altogether wanting ; in others the carboniferous slate only was absent, the lower 

 limestone resting directly on the yellow sandstone. In the northern and middle dis- 

 tricts of Ireland, the calp formed a very thick and important member of the series, 

 but gradually thinned out towards the south ; it had not yet been discovered in the 

 counties of Cork and Waterford, and was only occasionally traceable in Clare, Lime- 

 rick and Kerry. In the middle district, the upper limestone formed the distinguishing 

 feature ; in the southern section, the upper and lower limestones were most abun- 

 dant, and the calp least so, whilst the carboniferous slate and yellow sandstone oc- 

 cupied an inconsiderable superficial extent, but were important, as they contained a 

 great variety of fossils. The carboniferous slate of the South of Ireland differed con- 

 siderably in lithological character from that of the middle and northern regions, but 

 the number of fossils common to the beds which occupy the same geological position 

 in all three districts, showed the necessity of including the whole in one division. In 

 the tables of fossils before mentioned, the occurrence of each species in the different 

 members of the Irish series, was indicated for each of the three districts, and also 

 their occurrence in North Devon, and in the English mountain limestone. From 

 these general tables, Mr. Griffith had prepared tables of results, showing the number 

 of fossils of each class occurring in every division of the mountain limestone of Ire- 

 land ; those peculiar to it, those common to it, and all the other members of the 

 series, those that are common to each of the other divisions, and also those that are 

 common to the mountain limestone of Great Britain, and to North Devon. Some 

 of the results obtained were as follows : — Yellow sandstone, out of 122 fossils, 9 were 

 peculiar to it: 113, or 92^ percent., common to the mountain limestone of Ireland 

 generally; 49 species, or 40 per cent., common to the upper limestone; 87. or 71 

 per cent., to the calp ; 75, or 61 per cent., to the lower limestone, and 94, or 77 per 

 cent., common to the carboniferous slate; 35 species, or 30 per cent., were common 

 to North Devon; and 59, or 48 per cent., to the mountain limestone of Great Britain. 

 — Carboniferous slate, of 275 fossils, 12 were peculiar to it ; 263, or 95J per cent., 

 common to the mountain limestone of Ireland generally; 99, or 36 per cent., com- 

 mon to the upper limestone; 176, or 64 per cent., to the calp; 162, or 60 percent., 

 to the lower limestone; and 94, or 34 per cent., common to the yellow sandstone; 

 65 species, or 24 per cent., were common to North Devon ; and 139, or 50 per cent., 

 to the mountain limestone of Great Britain. From these data Mr. Griffith concluded, 

 that the yellow sandstone, which contained 92J per cent., and the carboniferous slate, 

 which contained 95| per cent, of fossils common to the other members of the moun- 

 tain limestone of Ireland, must belong to that series. Mr. Griffith next proceeds to 

 consider whether the mouutain limestone of Ireland generally should be classed with 

 that of Great Britain. By the table of results it appeared, that out of 180 species of 

 fossils obtained from the upper limestone, 133, or 73 per cent., were common to the 

 British mountain limestone ; of the calp, out of 267 species, 148, or 55 per cent., and 

 of the lower limestone, out of 391 fossils, 234, or 60 per cent., of the carboniferous 



