GEOLOGICAL DISTRIBUTION. 101 



as those of the Yorkshire beds, but the same forms of Hyalostelia and Beniera can 

 be recognised in them. 



At the head of the Gwydfyd Valley, on the Great Orme's Head, there are 

 portions of broken-up beds of white and bluish cherty rocks, which have been 

 described by Mr. George Maw, F.L.S., 1 and estimated by him to be about 50 feet 

 in thickness. They apparently belong to the series above the Carboniferous 

 Limestone ; the fragments are filled with spicules, principally minute acerates, 

 similar to those in the beds at Gronant. 



Scotland. — The beds which have yielded the remarkable series of Sponge 

 remains in Ayrshire, belong to what is known as the Upper- Limestone and Lower- 

 Limestone series of the Scotch geologists, which are situated beneath the Millstone- 

 grit, and thus on the horizon corresponding to the Yoredale series of Yorkshire 

 and North Wales, in which Sponge-beds are so largely developed. 



In Ayrshire, however, the Sponge-remains 2 have principally been obtained from 

 decayed material in the joints and fissures in the limestone, and in soft, siliceous 

 clays infilling irregular cavities in the same rock. Mr. John Smith, of Kilwinning, 

 has supplied me with the following list of localities in Ayrshire which have yielded 

 Sponge-spicules; Stacklawhill, thirty feet above the Linn-Spout Limestone; Glencart, 

 Lambridden, Linn Spout, and Monkcastle, in the Upper-Limestone series ; Birkhead, 

 Thirdpart, Blackstones, Cunningham Baidland, Low Baidland, Law, and Auchens- 

 keith, in the upper part of the Lower-Limestone series ; and Crawfield in the lower 

 part of the same series. Other localities are Dockra, Hillhead, near Beith, and 

 Dunlop, Ayrshire. They have also been met with in the limestones at Corrie- 

 burn, Campsie Hills, near Kirkcaldy, Fifeshire, near Linlithgow, Charlestown 

 Quarry near Inverkeithing, Roscobie Quarry, near Dunfermline, Macbiehil, Peebles, 

 near Cupar, and near Dalkeith. The forms most widely distributed are the 

 anchoring spicules of Hyalostelia and the cylindrical spicules of Beniera ; in the 

 Ayrshire district these are accompanied by the remarkably large spicules of Geodites, 

 Asteractinella, Tholiasterella, and Acanthactinella. Though the beds of Sponge 

 remains in Scotland are of much less thickness than those of Yorkshire and North 

 Wales, yet, owing to the preservation of the spicules in loose materials, they have 

 yielded a greater number of species. 



Ireland. — A well-marked series of Sponge-beds, hardly inferior in importance 

 to those of Yorkshire and North Wales, is developed in the so-called Upper Lime- 

 stone of the Carboniferous series of the Irish Geological Survey. The Sponge- 

 beds principally occur in the higher portions of the Upper Limestone, and they have 

 been included with this as the equivalents of the Carboniferous or Mountain Lime- 



1 ' G-eol. Mag.,' vol. ii, 1865, p. 200. 



2 ' Catalogue of the "Western-Scottish Fossils,' 1876, p. 36 ; also ' Proc. Nat. Hist. Soc. Glasgow,' 

 1882, p. 234. 



