13 



boniferous limestone are, as it were^ thrown out en echellon from 

 the circumference of the coal-field into the area of the old red sand- 

 stone- 



This portion of the memoir concluded with a comparison between 

 these violent yet local disturbances which have dislocated the carbo- 

 niferous limestone and old red sandstone, and that great movement 

 from north-east to south-west, which in Brecknockshire and Caermar- 

 thenshire threw up the mural ridge formed of the lowest beds of the old 

 red sandstone and the Ludlow rocks or upper member of the grau- 

 wacke series. It is also shown that although this ridge of transition 

 rocks passes in one part of its course within three miles of those 

 disturbances, which subsequently convulsed the coal-measures, yet 

 still preserves the true south-westerly strike in an unbroken line, as 

 if unaffected by them. 



Jan. 22. — Alexander Trotter, Esq., of Orchard Street, and Robert 

 Walters, Esq., of Lincoln's Inn Fields, were elected Fellows of this 

 Society. 



A paper was read " On the Structure and Classification of the 

 Transition Rocks of Shropshire, Herefordshire and part of Wales, 

 and on the Lines of Disturbance which have affected that Series of 

 Deposits, including the Valley of Elevation of Woolhope," by 

 Roderick Impey Murchison, Esq., F.R.S., F.G.S., &c. 



I. Another summer's work, during which the author revisited 

 Shropshire and the Welsh counties, formerly described, and also 

 examined the eastern side of Herefordshire, with portions of Mon- 

 mouth, Gloucester, Worcester and Staflbrdshires, has enabled him 

 to laj'^ before the Geological Society much more copious inforuialion 

 respecting the " Transition rocks," or " Fossiliferous Grauwacke" 

 of this quarter of Great Britain; and to subdivide the same into 

 formations. 



The following classification is, therefore, substituted for that pro- 

 posed last year, being founded upon more extensive observation 

 and an increased knowledge of the organic remains and the order of 

 superposition. 



1. Ludlotv Rocks. — Commencing beneath the old red sandstone, 

 described in the memoir read before the Society, January 8th, he 

 names the superior formation of the grauwacke series, the " Ludlow 

 rocks." This sandy, argillaceous deposit, has in its centre, the zone 

 of limestone well known at Aymestry, Downton on the Rock and 

 other places, by its containing in abundance the Pentamerus 

 Knightii. It is stated that the black limestone of Sedgeley, near 

 Dudley in Staffordshire, is identical in character and in organic re- 

 mains with that of Aymestry in Herefordshire, and the Yeo edge 

 in Shropshire, and that this calcareous zone is everj'where separated 

 from the W^enlock and Dudley limestone by a thick deposit of shale 

 and fiag, to which the author has assigned the name of " Lower 

 Ludlow rock". For the chief characters and order of superposition 

 of the groups of this formation and all those of the descending 

 series, the reader is referred to the annexed tabular view, in antici- 

 pation of details and illustrations which will, at some future time, be 



