228 PROCEEDINGS OF THE GEOLOGICAL, SOCIETY. 



Horderley Sections, ^c. 



The section along the Onny has so often been described, that no 

 gleanings, it might be thought, could be gained from it. But having 

 during a former year traced what I regarded as true Caradoc species 

 considerably within the limits of the Wenlock shale as coloured in 

 the Government Survey ; and having found, through the help of my 

 friend Mr. Duppa, of Cheney Longville, the Ti'inucleus Caractaci 

 in great abundance within less than 100 yards of Stretford Bridge, I 

 was very anxious to obtain Professor M 'Coy's help in determining a 

 more correct boundary between the contiguous shales of the Caradoc 

 and Wenlock groups. On the banks of the Onny I met, however, with 

 a great disappointment, as all the critical beds, in consequence of the 

 previous rains, were under water ; but I hope before long to be enabled, 

 through the kindness of Mr. Duppa, to exhibit to the Society a good 

 series of the fossils from the shales immediately above Stretford 

 Bridge. In another respect I was more fortunate ; for in making a 

 traverse along the Bishop's Castle road from Horderley to the spur 

 that descends from the Longmynd, Professor M'Coy discovered a few 

 species of Caradoc fossils in a part of the country which is coloured 

 Wenlock shale in the Map of the Survey. We therefore con- 

 cluded, that here, as along the Onny, a thick mass of Caradoc 

 shale overlies the Pentamerus or Hollies limestone*, and that the 

 colour of the Wenlock shale must be considerably contracted. The 

 same remark makes it also probable, that the dislocated shales on 

 the road from Horderley to Church Stretton (coloured as Llandeilo 

 in the Map of the Survey) belong to the Caradoc shales rather than 

 to the lower portions of the Bala group. This is however a minute, 

 and perhaps doubtful point, which I wish not to discuss. 



The order of succession, in the country here under notice, appears 

 therefore to be as follows: — (1.) Caradoc sandstone, &c., ending 

 nearly with the Pentamerus or Hollies limestone; (2.) Caradoc shale; 

 (3.) Wenlock shale ; (4.) Wenlock limestone, &c. Where then are 

 we to place the May Hill beds ? We can only reply, that they do not 

 appear in the section. They may have thinned off so as not to have 

 left their representatives in this portion of the deposits : or they may 

 have been covered up by a slight discordancy of position, which has 

 brought the Wenlock shales into contact with Caradoc rocks that 

 are midoubtedly older than the sandstones of May Hill. 



Whatever hypothesis we adopt, there is no greater difficulty pre- 

 sented by the section here under notice, than there is in sections, 

 formerly described by myself, through the country on the north- 

 eastern flank of the Berwyn chain. For example, commencing in 

 the valley of the Ceiriog and taking a north and south section across 

 the valley of the Dee, near Llangollen, we have a part of the upper 

 Bala group immediately overlaid by beds of the Wenlock age, with- 

 out any apparent want of conformity or true continuity. Yet it is 

 evident, on an extended comparison vdth the neighbouring groups, 



* The limestone alluded to in the text contains, as is well known, the Penta- 

 merus Icevis and Pentamerus oblongus in very great abundance. 



