160 BRITISH PALEOZOIC SPONGES. 



when mounted in Canada balsam, are translucent, and in some instances quite trans- 

 parent. They are all siliceous, and the silica is either chalcedonic or crystalline. 

 As a rule the axial canals are abnormally enlarged ; in some cases the wall of the 

 spicule is reduced to a thin crust inclosing the canal, and even this is occasionally 

 destroyed, and merely the solid infilling of the canal remains. The anchoring-rods 

 have precisely the same appearance, and are in the same state of preservation as the 

 skeletal-spicules. The anchoring-spicules occurring in the Yoredale rocks at 

 Richmond, Yorkshire, have a translucent, horny aspect ; they consist of chalcedonic 

 silica. 



This species is very abundant and widely distributed in the Lower Carboniferous 

 of Scotland, and in the cherts and limestones of the Yoredale series of Yorkshire. 

 In some places beds of rock, six inches ("015 m.) in thickness, are made up of bands 

 of the anchoring-spicules crossing over each other in a generally horizontal direction, 

 and it is probable that many of the Sponge-beds, mentioned in the Introduction, 

 principally consist of the detached spicules of this species. As already mentioned, 

 some of the anchoring-spicules are met with in the Ordovician strata of Girvan, 

 Ayrshire. This species may be distinguished from Hyalostelia parallela, M'Coy 

 sp., by the much more robust character of the spicular rods. 



Distribution. — Carboniferous, Yoredale series : Yorkshire, — Richmond, Arken- 

 dale, near Muker ; Gunnerside Gill, Swinner Gill, Sargill Beck, and throughout 

 Swaledale generally, where the main chert crops out. Flintshire, — Halkin, Henblas, 

 near Holywell. 



Scotland. — Upper part of Lower Limestone series : Cunningham Baidland, Low 

 Baidland, Auchenskeith, Thirdpart, Hourat, Law, Birkhead, Blackstone, Dairy. 

 Upper Limestone series : Linn Spout, Glencart, Lambridden, Dairy, Ayrshire ; 

 Gateside, Beith ; Brockley, Lesmahagow ; Ponniel Water, Douglas. Messrs Young 

 cite also the following localities : Dockra, Hillhead and Trearne quarries, near 

 Beith ; Waterland Quarry, Dunlop, Ayrshire ; Corrieburn, Campsie Hills, Bathgate, 

 Chapel Quarry, near Kirkaldy, Fifeshire. Mr. R. Etheridge, junr., also records 

 this species from Petershill and Galabraes quarries, near Bathgate; Tartraven old 

 quarry, near Linlithgow; Charlestown Quarry, near Inverkeithing ; Roscobie 

 Quarry, near Dunfermline; Laddedie Quarry, near Cupar; Airfield, near Cousland, 

 by Dalkeith. 



Ireland. — Calp series : Bundoran, Co. Leitrim, Tyrone. Upper Limestone 

 series : Ben Bulben, near Sligo. 



