646 MISS E. M. K. WOOD ON THE [Xov. 1906, 



Wales they lie transgressively and quite uncouformably on various members 

 of the Lower Silurian Series. On the other hand, both in Wales and Shrop- 

 shire, they pass conformably under the lowest beds of Wenlock Shale, with 

 which undoubtedly they are intimately connected.' 



Beyond an occasional reference to the ' Tarannon Shales ' in 

 various memoirs and text-books, no subsequent stratigraphical 

 account of this band has been published. 



Thus, if we rely solely upon the descriptions and maps of the 

 Geological Survey, the ' Tarannon Shales ' as a group must be 

 younger than the Upper Llandovery and older than the Wenlock 

 Shale. But whether these i Tarannon Shales' answer to the whole 

 or only to a part of the period intervening between the Upper 

 Llandovery and Wenlock, or whether their alliances are more with 

 the former than with the latter, or vice versa, are questions which 

 cannot be determined from the stratigraphical evidence hitherto 

 published. 



Neither at the time when the ' Tarannon ' Beds were originally 

 mapped, nor for many years after, were any fossils obtained from 

 these rocks. It was impossible, therefore, for the geologist either 

 to estimate their systematic range in geological chronology, or to 

 recognize their equivalents elsewhere. 



Southern Scotland.' — The first light upon the palaeontological 

 side of the question came from Scotland. In the year 1870 

 Prof. Lapworth 1 described a massive series of strata, overlying the 

 Black Shales of Moffat and characterized by a special graptolitic 

 fauna, underthe title of the Gala Group. He divided this group 

 into :— (1) Abbotsford Flags, (2) Gala Grits, (3) Buckholm Grits, 

 and (4) Grieston Beds. Founding his correlation on the view (then 

 generally received) of the Upper Llandeilo age of the underlying 

 Moffat Shales, he assigned the Gala Group to the Caradoc or Bala. 



In the year 1878 2 he published the results of his graptolitic zonal 

 work on the Moffat Series, showing that it included not only the 

 Upper Llandeilo but also the Caradoc and Lower Llandovery. 

 Thus he carried up inferentially the base of the Gala to the Upper 

 Llandovery ; and, further, since he had already shown in his 

 paper on the Scottish Monograptidae 3 that the highest beds of the 

 southern representative of this Gala Group (Hawick Beds) pass up 

 conformably into the Riccarton (Wenlock) Beds, the Gala Group as 

 a whole should not only include the Upper Llandovery, but also the 

 representatives of the Tarannon. 



In the year 1879 Prof. Lapworth 4 discovered fossils in the band 

 of ' Tarannon Shale ' of the Geological-Survey maps at Conway 

 (North Wales), and these forms included several of the graptolites 



1 Trans. Edin. Geol. Soc. vol. ii (1869-74) p. 46, & Geol. Mag. vol. vii 

 (1870) pp. 204-209 & 279-84. 



2 Quart. Journ. Geol. Soc. vol. xxxiv (1878) pp = 240, etc, 



3 Geol. Mag. dec. ii. toI. iii (1876) pp. 308, etc. 



4 Ann. & Mag. Nat. Hist. ser. 5, vol. v (1880) p. 367, & vol. vi (1880) 

 pp. 200 & 204. 



