STRATA OF SHROPSHIRE AND DENBIGHSHIRE. 23 



the Permian strata; this limestone is traceable over a large portion 

 of that coal-field. From Mr. Howell's description, I imagine that 

 the sandstones and breccias of group 2 are not much represented in 

 the district, and that the calcareous conglomerates interstratified 

 between purple sandstones and red marls belong mostly to group 3 

 of my sections. The sandstones and marls of group 4 were proved 

 in a boring near the town of Warwick; but detailed sections of this 

 group are much needed. 



Section 16 represents the magnesian conglomerate of Somerset- 

 shire. I have felt considerable hesitation in including this section 

 among Permian strata, because of the degree of uncertainty which 

 seems to prevail as to its true stratigraphical position. Mr. 

 Etheridge, in his able memoir on the subject*, reasoning chiefly 

 from fossil evidence, places it towards the base of the Keuper sand- 

 stone. In the sections of the Geological Survey, its true position is 

 left somewhat an open question. Local geologists also appear 

 undecided on the matter. Prof. Sedgwick, in 1832, spoke of its 

 resemblance to the Alberbury conglomerate, and placed it on the 

 same horizon as that deposit f . 



In 1854 Sir R. I. MurchisonJ described this conglomerate as having 

 " usually been placed on the same parallel as the Magnesian Lime- 

 stone of the north of England ; and the analogy of the succession in 

 Shropshire, where the Lower Eed Sandstone is interpolated between 

 the coal-fields beneath and the magnesian conglomerate, favours the 

 view." Prof. Phillips§ described these lower beds as " red or claret- 

 coloured sandstones and marls, chiefly the former." Probably this 

 diversity of opinion is owing in part to the fact alluded to by Prof. 

 Ramsay as shown by Sir Henry De la Beche, that the conglomerates 

 of the district are ofvarious ages; so that the different authors may be 

 speaking of conglomerates of ages widely apart. Personally I only 

 know the conglomerates of the country between Wells and Shepton 

 Mallet; and on reviewing the whole question, I am inclined, from the 

 great similarity in colour and composition, as well as from the ap- 

 parently greater similarity of the underlying sandstones and marls 

 to those of Permian than to those of Triassic age, to regard the con- 

 glomerates generally as belonging to the former period rather than 

 the latter. The inferences drawn in this paper, however, are not 

 affected by this question ; and the section need not be taken into ac- 

 count by those who differ from my opinion of the age of these con- 

 glomerates. 



Section 17 is the original typical English section, as given by Prof. 

 Sedgwick in 1832. And really, when I look at the completeness of 

 that section, exhibiting, as it does, all the groups in almost every 

 known variety of strata, and read the lucid and comprehensive memoir 

 in which they are described, I wonder that English geologists were 



* " The Geological Position of the Dolomitic Conglomerate of the Bristol 

 area," Quart. Journ. Geol. Soc. May 1870. 

 t " On the Magnesian Limestone," Geol. Trans, vol. iii. 2nd series, p. 64 ctseq. 

 t Siluria, p. 302. 

 § Memoirs of the Geological Survey, vol.jL p. 256. 



