68 The Irish Naturalist, [March, 



THE BRACHIOPODA AND MOLLUSCA 

 OF THE CARBONIFEROUS ROCKS OF IRELAND. 



Irish Fossil Sheiks and their Modern 

 Representatives. 



by arthur h. foord, ph.d., f.g.s. 



(Plate 5). 

 (Read before the Dublin Naturalists' Field Club, December 13, 1898). 



Underlying the more superficial deposits of clay, sand, 

 gravel, or peat, is an immense area, about one-half of that 

 of the whole of Ireland, occupied by the sedimentary and 

 other rocks belonging to the Carboniferous system, which 

 represents, together with the Permian, the uppermost division 

 of the great Palaeozoic group. 



I may shortly explain that the sedimentary or aqueous 

 rocks were derived from the waste of the land, that is of older 

 rocks, and were laid down in the sea as sediments, the agents 

 in this process being the waves, rivers, frost, and other dis- 

 integrating forces, operating through incalculable periods of 

 time. 



The chief distribution of the Carboniferous system in 

 Ireland is in the great central plain, the rocks there being 

 mostly limestone, but the system extends also to the coasts 

 both south and west, and, in a more limited degree, north and 

 east. 



Three divisions are generally recognized in it, the upper- 

 most of which is termed the Coal-measures, and consists of 

 sandstones, shales, and coal seams. The lowest is the 

 Carboniferous Limestone, in England called the Mountain 

 limestone. The middle division, a coarse sandstone, is 

 known as the Millstone Grit ; this last forms the frowning 

 cliffs of the rock-bound coast of Clare, of which county it 

 occupies a considerable area, extending also into Limerick, 

 Kerry, and Cork. The Coal-measures in Ireland are un- 

 fortunately represented by only a few isolated patches in 

 Tyrone, Tipperary, and Kilkenny, any extension of these, if 

 such existed, having been completely denuded away. These 

 different types of rock, when their derivation is considered, 

 throw much light upon the geographical conditions of the 



