418 MR. A. WADE ON THE LLANDOVERY AND [Aug. 191 I 



The work done by Miss Elles and Miss Wood [9] & [10] in 1900 

 in the Wenlock and Ludlow beds of the neighbouring Long Moun- 

 tain district is now classical. 



III. Straticraphtcal Literature. 



[1] 1839. Sir Roderick I. Murchison, ' The Silurian System ' Chaps, xxiii & 



xxiv. 

 [2] 1854. Sir Eoderick I. Murchison, ' Siluria ' 1st ed. ; 1872, 5th ed. 

 [3] 1866. Sir Andrew C. Ramsay, 'The Geology of North Wales' 1st ed., 



Mem. Geol. Surv. vol. iii ; 1881, 2nd ed. 

 [4] 1885. W. W. Watts, 'On the Igneous & Associated Rocks of the 



Breiclden Hills in East Montgomeryshire & West Shropshire ' 



Q. J. G-. S. vol. xli, p. 532. 

 [5] 1890. J. Bickerton Morgan, 'On the Strata forming the Base of the 



Silurian in North-East Montgomeryshire' Rep. Brit. Assoc. 



(Leeds) p. 816. 

 [6] 1885 J. Bickerton Morgan, ' Montgomeryshire Collections ' vol. xviii, 



& 1891. p. 149 & vol. xxv, p. 359. 

 [7] 1890. W. W. Watts, ' The Geology of the Long Mountain, on the Welsh 



Borders.' Rep. Brit. Assoc. (Leeds) p. 817. 

 [8] 1890. T. Rupert Jones, 'On some Palaeozoic Ostracoda from North 



America, Wales, & Ireland ' Q. J. G. S. vol. xlvi, p. 1. 

 [9] 1900. Miss G. L. Elles, ' The Zonal Classification of the Wenlock Shales 



of the Welsh Borderland' Q. J. G. S. vol. lvi, p. 370. 

 [10] 1900. Miss E. M. R.Wood [Mrs. Shakespear], 'The Lower Ludlow 



Formation & its Graptolite Fauna' Q. J. G. S. vol. lvi, p. 415. 

 [11] 1904. H. S. Jevons. 'Note on the Keratophyres of the Breidden & 



Berwyn Hills' Geol. Mag. dec. 5, vol. i, p. 13. 

 [12] 1905. W. W. Watts, ' On the Igneous Rocks of the Welsh Border' Proc. 



Geol. Assoc, vol. xix, p. 173. 



IV. The Stratigraphical Succession. 



Before dealing in detail with the stratigraphical succession, I 

 think it well to tabulate the full sequence obtained as a result of 

 my investigations over the whole area. This is owing to the fact 

 that a complete sequence cannot be established by any single 

 section, in consequence partly of the overlapping of certain of the 

 higher series, and partly (in all probability) of the thinning-out of 

 beds in the area. The district is one of transition, and in many of 

 its characters constitutes a connecting-link between neighbouring 

 areas on every side. This feature has made it necessary to dis- 

 tinguish between a western facies and an eastern facies in certain 

 cases. 



The different group-names have been chosen to indicate places 

 where the beds are best exposed and, as a rule, most fossiliferous. 



