Vol. 62.] TAKAMNON SEEIES OF TAKANtfOlS'. 647 



characteristic of his Lower Gala Group of the South of Scotland, 

 as distinct from those of the Moffat Shales (Upper Llandeilo- 

 Llandovery) below, and the Eiccarton (Wenlock) Beds above. 

 Therefore, in the following year (1880), he was able to assert, in 

 his paper on the < Geological Distribution of the Rhabdophora/ 

 that the 



' Tarannon Shale of Wales .... occupies the systematic place of the Gala 

 Group, to which, however, it is vastly inferior in vertical thickness and in the 

 richness and variety of its graptolite-fauna.' (Op. cit. vol. v, p. 367.) 



In the Table at the end of that paper (vol. vi, p. 204) he assigns the 

 whole of the Gala or Queensberry Group and its equivalents in 

 Girvan to the Tarannon age, and divides the Scottish Tarannon 

 rocks into three graptolitic zones (op. cit. p. 200) : — (1) Rastrites 

 maocimus, (2) Monograptus exiguus, and (3) Cyrtograptus Gray 03; 

 the first of which he considers ' must be regarded as the zone of 

 transition ' between the Tarannon (Gala) and the preceding Llan- 

 dovery (Birkhill) formations. These views have subsequently been 

 generally adopted by strati graphists — with the exception, however, 

 that in most stratigraphical papers the zone of Rastrites maximus 

 is wholly assigned to the Upper Birkhill. 



But here it must be borne in mind that the assignation of these 

 three graptolitic zones to the Tarannon age was, to a certain extent, 

 a matter of inference, based mainly upon the facts that Lower Gala 

 fossils had been found at Conway and that the zone of Cyrtograptus 

 Murchisoni constituted the base of the "Wenlock at Builth and 

 elsewhere. 



North Y/ales. — A certain amount of additional light was thrown 

 upon the position of the ' Tarannon Shale ' by the palaeontological 

 discoveries in the older Llandovery and the newer Wenlock Beds in 

 North Wales. 



In 1880 Dr. Marr * reported Birkhill graptolites from the beds 

 immediately underlying the strata mapped as Tarannon Shales at 

 Cerrig-y-druidion. 



At a later date (1893) Mr. Lake and Prof. Groom recorded 

 Birkhill graptolites from the strata underlying the i Tarannon 

 Shales ' in the Corwen district ; and in the following year (1894) 

 Mr. Lake demonstrated the conformity of the local Tarannon to 

 the overlying Wenlock Beds with Cyrtograptus Murchisoni. 2 



In 1895 the ' Tarannon Shales ' of Conway were re-examined by 

 Miss Elles and myself 3 and were found to contain the distinct 

 faunas of the two zones of Rastrites maximus and Monograptus 

 ecciguus. No trace, however, was found of an Upper Gala fauna, 

 although Cyrtograptus Murchisoni was found in the Wenlock 

 Beds above. 



1 Quart. Journ. Geol. Soc. vol. xxxvi (1880) pp. 277, etc. 



2 Unci. vol. xlix (1893) p. 426, & vol. li (1895) p. 9. 



3 Md. vol. lii (1896) pp. 273, etc. 



Q.J. G. S. No. 248. 2i 



