Mr. Murchison on the Transition Rods of Shropshire, $c. 375 



Hills, and at Dudley in Staffordshire, a southerly movement has 

 affected both the transition rocks and the coal-measures. 



This part of the memoir was concluded by the notice of a very 

 remarkable case of dislocation, amounting to an entire reversal of 

 the two younger formations of the grauwacke series along a distance 

 of several miles upon the flanks of the Abberley Hills. In this tract 

 the Lower Ludlow overlies the Upper Ludlow rock, at angles 

 varying from 70° to 45° ; and the adjacent parallel ridge of the 

 Wenlock limestone is conformably tilted over, giving the appear- 

 ance of the Ludlow rocks passing beneath the older formation. This 

 phenomenon is supposed to have been brought about by the out- 

 burst of the contiguous trappean hills of Abberley and Woodbury, 

 the elevating forces accompanying which, it is conceived, have bent 

 them back upon their axes, and produced their present inverted po- 

 sition. This mode of explanation, it is stated, is rendered conclusive 

 on tracing the same sedimentary groups to those points where, from 

 their south-south-easterly direction they impinge upon the sienite 

 of the Malvern chain, and where the same phsenomenon of reversal, 

 on a small scale, is again apparent. Here the strata near the sienite 

 are bent backwards; but those which are removed from it not having 

 been disturbed in so great a degree, incline towards the west, the 

 Wenlock and Dudley limestone dipping beneath the exterior and 

 upper zone of Ludlow rocks. 



In further illustration of the country of which he has undertaken 

 the review, the author announced as future communications — 



1st, A special notice of the Ludlow and Wenlock formations as 

 they appear at Sedgeley and Dudley in Staffordshire, and of their 

 relations to the coal-measures of that district. 



2ndly, A sketch of the gravel and alluvial deposits of Hereford- 

 shire and the surrounding counties. 



3rdly, On certain new lines of demarcation which he has estab- 

 lished between the old and new red sandstones in Shropshire, Wor- 

 cestershire, Hereford and Gloucestershire ; with some observations 

 on the coal-fields of Pensax, Billingsley, Deuxhill and Sherlot in 

 Salop. 



4thly, An account of the trap rocks in the country described, 

 including basalts, green-stones, porphyries and sienites, and of the 

 effects produced at their points of eruption through the sedimentary 

 deposits. 



Feb. 5. — A paper was first read " On some of the Faults which 

 affect the Coal-field of Coalbrookdale," by Joseph Prestwich, jun., 

 Esq., F.G.S. 



In this communication the author confines his observations al- 

 most entirely to the direction of the principal faults, and to the 

 changes which they have produced in the relative position of the 

 beds of coal ; and he refers to the memoirs of Mr. Murchison for an 

 account of the formations on which the coal-measures repose. 



The author concludes his memoir with some observations on the 

 fossils he procured principally from the ironstone of these coal- 

 measures. Of 18 genera of shells which he enumerates, 12 are ma- 



