148 PROF. o. T. JOXEs ON [vol. Ixxvii, 



" Pentamerus Beds " could be identified with the " upper portion " of the 

 Caradoc developed at May Hill and the Malverns, and which has lately been 

 described by Professors Sedgwick and McCoy ' ^ 



It had been noted by A. C. Kanisay & W. T. Aveline in 1848 ^ 

 that a part of the Caradoc in Shropshire behaved in a different 

 manner from the rest of it, and persistently followed the base of 

 the Wenloek. Its fossils were enumerated by Forbes. 



Also J. A. Phillips ^ had shown that in the Malvern and 

 Abberley districts the so-called ' Caradoc ' was intimately con- 

 nected with the Woolhope Limestone, and no definite line of 

 separation could be drawn between them. The fossil lists from 

 the ' Caradoc ' and the Woolhope are closely alike, yet the remark- 

 able statement is made that 



' it is unquestionable that the former belongs, by its organic contents, to the 

 Lower Silurian group, and the other, by the same characters, is inseparately 

 linked with the Wenloek rocks ' (p. 74). 



Sedgwick's work furnished a read}^ explanation of these anomalies, 

 and marked a most important step in advance. They were further 

 elaborated in a paper read to the Geological Society on Ma}'" 3rd, 

 1854, of which, however, only a short abstract was jDublished by 

 the Society. The paper appeared subsequently in the ' Philo- 

 sophical Magazine' for 1854 (ser. 4, vol. viii, pp. 301, 359). 



The re-examination of the Shropshire area b}^ Aveline & Salter 

 led to most important results, not only in regard to the relations of 

 the rocks in that area, but also along the Welsh Borders. These 

 authors confirmed Sedgwick's views as to the distinctness of the 

 upper and lower portions of the Caradoc, and were able, also, to 

 establish the fact of a great unconformity between them. 



The}^ concluded from the fossil evidence that the t^^pical Caradoc 

 was equivalent to the Bala, and the overh^ing rocks to the May- 

 Hill Sandstone. Further, a band of purple and greenish shales 

 was observed everywhere between the Upper Caradoc sandstones 

 and the base of the Wenloek. It was this peculiar band which in 

 the succeeding two or three 3'^ears furnished the clue that brought 

 the Welsh rocks into relation with those of Shi-opshire. 



During a great part of the year following the publication of 

 the above-mentioned paper, Aveline was engaged in examining the 

 rocks lying west of the base of the Wenloek in the neighbourhood 

 of Llandovery and Builth, and in the district on the north. 

 During this surve}^ pale slates of the Shropshire t3qDe were observed 

 between the ^Pentamerus Sandstones' of Castell Craig Gwyddon, 

 north-east of Llandover}^, and the base of the Wenloek. As the 

 pale slates aiDpeared from their geological characters and position 

 to be equivalent to those of Shropshire, it followed that the 

 underljnng sandstones were the representatives of the Shropshire 

 Pentamerus Beds. This view Avas confirmed by Salter from 



1 W. T. Aveline & J. W. Salter, ' On the '• Caradoc Sandstone " of Shrop- 

 shire ' Q. J. G. S. vol. X (1854) pp. 62-63. 



2 lUd. vol. iv (1848) p. 294. 



2 Mem. Geo]. Surv. vol. ii (1848) pt. 1. 



