TRANSACTIONS OF SECTION C. 559 



Killey Bridge Beth. 



( Upper.) Soft, calcareous, grey mudstones, with Jiemopleiirides and Di'plo' 



graptiis truncatus. 

 (Loicer.) Soft, ferruginous, blue or yellow mudstones, with numerous 

 ■ Tri)iucleus and Ampi/.v. 



Bardahessiag Beds. 



( U2^)er.) Hard, calcareous flags and grits, with Lichas, Phacops hibernicus, 



Staurocephalus, Sec, and Strophomena. 

 {Lower.) Softer, uncompacted grits, sandstones, and conglomerates, with 



large Strophomena and occasional Orthis. 



The Desertcreate Group finds its closest parallel in the Drummuck beds of 

 Girvan, while the Little River Group is most like the Birkhill shales of MolFat. 

 The whole series is overlain unconformably by the Dingle beds of the local Old Red 

 Sandstone, and with that formation has been folded into a remarkable series of 

 shallow isoclines, trending a little south of east and north of west, and having a 

 general southerly pitch. The total thickness of the Desertcreate and Little River 

 Groups together does not exceed 500 feet. 



4. Becent Exjwsures of Glacial Drift at Doricaster and Tickhill. 

 By H. CuLPiN and G. Grace, B.Sc. 



Reference was made to the wide area of the well-known Boulder-till at Balby, 

 near Doncaster. 



A description was then given of an exposure of Boulder-clay obtained in the 

 sinking of the Bentley Coal Pit, two miles north of Doncaster. Here there is 20 feet 

 of clay with boulders of Permian Limestone, Carboniferous Limestones, grits and 

 gannisters, and Coal Measure shale, with Anthracoviya P/nllipsi. The clay is 

 at a depth of 55 feet to 75 feet below O.D., being covered by 80 feet of alluvial 

 clays, sands, and gravels. 



Particulars were given of cuttings on the South Yorkshire Joint Railway, 

 which in a distance of four to six miles south of Doncaster makes four exposures 

 of boulder debris, the most southern being at All Hallows Hill, Tickhill. The 

 maximum depth exposed is 20 feet, but this does not reach the base. In the 

 northern cutting the matrix is less clayey than at Balby, but the Tickhill deposit 

 is a typical tough till which is being excavated with the aid of explosives. The 

 boulders are mainly Permian Limestones, ranging up to 12 cubic feet in size, with 

 some Carboniferous grits and gannisters, and fairly numerous Carboniferous Lime- 

 Stones up to 2 feet cube. So far, only three boulders of Lake District volcanic ash 

 have been not"d. One of these is a foot cube. 



The paper concluded with a reference to the Permian and Carboniferous 

 boulders at Gringley-on-the-Hill, which is ten miles east of Tickhill, and (like the 

 latter) about forty miles south of York. 



5. Report on the Crystalline Rocks of Anglesey. — See Reports, p. 301. 



6. On Faults as a Predisposing Cause of the Existence of Pot-holes on 

 Inglehoroiigh. By Harold Brodrick, 



Ingleborough Hill consists of a large plateau of Carboniferous limestone about 

 400 feet in thickness and capped by a cone of Yoredale rocks with a summit of 

 Millstone Grit. On this plateau there are a large number of pot-holes or vertical 

 shafts in the limestone: there are upwards of thirty of these at present known to 

 exist, and it is probable that there are many more still covered with the deposit of 

 glacial drift. Within the l^st few years many facts have come to light which 



