Igneous and Associated Rocks of the Breidden Hills. 211 



the conclusion that we have at this depth the "Melbourne Rock" 

 with the zone of Belemnites plenus in a remanie condition at its 

 base. Some new facts concerning the state of preservation of the 

 fossils in the Chalk Marl are also recorded. 



With respect to the conclusions arrived at by the author concern- 

 ing the distribution of the Jurassic rocks on the south side of the 

 London Basin, an important piece of confirmatory evidence has been 

 supplied by a deep boring made at the Dockyard-Extension Works 

 at Chatham. This section, for the details of which the authors are 

 indebted to the officers of the Geological Survey, shows that under 

 the Chalk and Gault, with normal characters and thickness, there 

 lie 41 feet of sandy strata of Xeocomian age, and that these are 

 directly underlain by blue clays of Middle Oxfordian age, as is 

 proved by the numerous fossils which they have yielded. We have 

 now, therefore, direct evidence of the existence and position of strata 

 of Lower, Middle, and Upper Oolite age, respectively, beneath the 

 Cretaceous rocks of the south-east of England. 



2. " On the Igneous and Associated Rocks of the Breidden Hills 

 in East Montgomeryshire and West Shropshire." By W. W. Watts, 

 Esq., F.G.S. 



The author, in this paper, described the succession of rocks in the 

 small tract near the Breidden Hills situated between Welshpool and 

 Shrewsbury. The Cambrian rocks are : — 



(1) Criggion Shales, dark and barren, much penetrated by in- 

 trusive diabases and about 2700 feet thick. 



(2) Andesitic lavas and ashes, followed by conglomerates of the 

 same materials. 



(3) Ashy grits and shales containing Climacograpsus antiquus?, 

 C. bicornis ?, C. Scharenbergi, Cryptograpsus tricornis, Diplograpsus 

 foliaceus, Leptograpsus flaccidusl, Beyrichia complicata, Trinueleus 

 concentricus, Orthis testudinaria, Bellerophon bilobatus. The rocks 

 are thus of Bala age, the fossils indicating that the ashy grits and 

 shales are on the horizon of the top of the Glenkiln or bottom of 

 the Hartfell series. 



These are followed by Silurian strata. 



(1) Pentamerus-be&s. Soft sandstones and mudstones yielding 

 Pentamerus globosus ?, P. oblongns, P. undatus, Leptcena transver- 

 salis, Strophomena rhomboidalis, Petraia mibduplicata. 



(2) Purple shales, unfossiliferous. 



(3) Lower Wenlock Shale, with Monograptus vomerinus ?, Crypto- 

 grapsus, sp., M. priodon, var. Flemingi. These graduate into : — 



(4) Upper Wenlock Shale, with M. priodon, M. vamerinns?,/ 

 M. basilicus, M. Nilssoni, M. Roemeri. 



(5) Lower Ludlow Shale. M. colonus, M. Nilssoni, M. Salweyi, 

 M. lintwardenensis. 



The paper concluded with microscopical descriptions of the igneous 

 rocks, of which there are two sets : — 



(1) An older set interbedded with the Cambrian and consisting of 

 andesites bearing a large percentage of a mineral allied to enstatite. 



