RH.ETIC BEDS. 247 



the coast of Yorkshire, to near Lyme Regis and Axmouth on 

 the coast of Devonshire. 



The occurrence of Rhcetic Beds in Cumberland has not been 

 proved, but their presence may be inferred from an outlying 

 mass of Lower Lias situated to the west of Carlisle, and from 

 the occurrence of Rhostic Beds in the north-east of Ireland, for in 

 this northern area the outcrop of the Rhsetic Beds (if present) is 

 entirely concealed by Drift. Nor have any definite traces of 

 Rhgetic Beds been found in the superficial deposits, perhaps 

 because the Beds are represented by soft shales and marls, which 

 would not readily be preserved in Boulder-drift.^ 



In Yorkshire the Rhsetic Beds comprise about fifteen feet of 

 shales with sandy beds, resting on about ten feet of blue or tea- 

 green marls. The highest beds are nowhere well exposed. A 

 band with Pknromya Crocornbeia (known as Plniromya-\\vs\&?XowQ^ 

 has been taken as the base of the Lower Lias ; although this 

 species, first described by Mr. C. Moore from the White Lias of 

 Beer Crocombe in Somerset, is also a Rhaetic fossil. The beds 

 are not exposed on the coast, but they occur at Lazenby, south- 

 west of Redcar, and they may be seen at intervals, near Stokesley, 

 also to the east of Northallerton, between York and New Malton, 

 and at Londesborough, north of Market Weighton.- 



In Lincolnshire, Nottinghamshire, and Leicestershire the White 

 Lias is represented by fifteen or twenty feet of grey and yellow 

 marls and shales with nodules of earthy limestone. The section at 

 Gainsborough was first described by I\Ir. F. M. Burton,^ and the 

 beds have been traced northwards to Burton-upon-Stather by Mr. 

 W. A. E. Ussher. At Newark-upon-Trent, a sharp line of demarca- 

 tion, suggestive of local unconformity, has been noticed between the 

 Black Shales and underlying Red Marls.* Sections of Rhsetic Beds 

 have been exposed in the railway-cuttings at Elton, near Notting- 

 ham,* and near Barrow-on-Soar.*' The thickness of the Rha^tic 

 Beds at the Spinney Hills, near Leicester, has been estimated at 

 twenty-six feet, whereas at Wigston the Black Shales are about 

 forty feet in thickness, and these overlie about fifteen feet of tea- 

 green marls.'' 



In Warwickshire the White Lias may be studied at Rugby, 

 Southam, Loxley, and Eatington ; while near Stratford-on-Avon, 

 it is represented by the 'Guinea-bed' of Binton, Grafton, Wilmcote, 

 and Bickmarsh, a limestone which is sometimes conglomeratic. 



^ T. V. Holmes, Q.J. xxxvii. 293. 



2 Phillips, Geol. Yorks, Part I, edit. 3, p. 23; R. Tate and J. F. Blake, 

 Yorkshire Lias, p. 30 ; C. F. Strangways, Geol. N.E. of York (Geol. Survey), 

 p. 6. 



3 Q.J. xxiii. 315. 



* See Geol. S. W. Lincolnshire, by A. J. Jukes-Browne, p. 19 ; G. Mag. 1874, 

 p. 480. 



* E. Wilson, Q. J. xxxviii. 451 ; see also Midland Naturalist, vi. 193 ; and 

 Rev. A. Irving, G.Mag. 1874, p. 318, P. Geol. Assoc, iv. 82. 



^ W. J. Harrison, Q. J. xxxii. 212. 



" E. Wilson and H. E. Quilter, G. Mag. 1884, p. 415. 



