334 



C, LAPWORTH ON THE MOFFAT SERIES. 



zones of the Moffat Series, as detailed in the preceding portion of 

 this paper, all reference to the identical results arrived at in other 

 districts by British and continental paleontologists would here be 

 superfluous. 



That none of the Moffat Shales are of Arenig age is clear from the 

 complete absence within them of those complex forms of Bkliograpti 

 and Phyllograpti which constitute so striking and characteristic 

 a feature of the Graptolitic fauna of the Skiddaw Slate and its "Welsh 

 and Canadian equivalents. That none of them appertain to the true 

 Upper Silurian, as at present understood by the majority of geologists, 

 is fully as evident, from the fact that they are similarly destitute of 

 all the known peculiar Upper Silurian forms. Our search for their 

 extra- Scottish equivalents must therefore be restricted to the three 

 successive formations of the Llandeilo, Bala, and Lower Llandovery. 

 Let us pass the respective Graptolite faunas of these in review. 



(a) Llandeilo Formation (Llandeilo-Flags of Murchison). 



From the valuable and accurate papers of Mr. Hicks*, and the 

 general results of the special study of the Welsh Graptolites made 

 by Mr. John Hopkinson, we learn that the Llandeilo beds of South 

 Wales, in the typical localities of Llandridod, Meadow Town, and 

 Abereiddy Bay, have afforded the following species : — 



Diplograptus foliaceus (Murch.). 

 dentatus (Brongn.). 



Lepfcograptus flaccidus (Hall). 

 Dicellograptus divaricatus (Hall) 



sextans (Hall). 



Dicranograptus ramosus (Hall). 

 formosus (Hopfc.). 



tricornis (Carr.). 



Olimacograptus cselatus (Lapw.). 

 Scharenbergi (Lapw.). 



The general facies of this assemblage is clearly that of the Glen- 

 kiln Shales, in which all the foregoing species are abundant, and to 

 which in South Scotland many are strictly peculiar. In South 

 Wales, however, they are almost invariably associated with forms of 

 Didymograptus of the type of D. Murchisoni, and sometimes with 

 species of Pliyllograptus, none of which have ever been detected in 

 the Moffat Series. 



In one locality among the Llandeilo beds of Forth Wales these 

 distinctive forms are absent. The dark shales in the hills a few 

 miles to the north of Tremadoc, which have been mined for copper, 

 but whose precise position is yet undetermined, have afforded to 

 Messrs. Salter f and Hopkinson % the following species, all of which 

 are common Glenkiln forms : — 



Dicellograptus divaricatus (Hall). 



sextans (Hall). 



Dicanograptus ramosus (Hall). 

 Coenograptus gracilis ? (Hall). 

 Diplograptus foliaceus {Hall). 

 ? Whitfieldi (Hall). 



Diplograptus ? Hincksi (Hopk.). 



tricornis (Carr.). 



Olimacograptus bicornis (Hall). 



Scharenbergi (Lapw.). 



Didymograptus superstes (Lapw.). 

 Thamnograptus typus? (Hall). 



Judging from the absence of Didymograptus Murchisoni and of the 

 genus Phyllograptus, and the presence of some of the succeeding Bala 



* Quart, Journ. Geol. Soc. vol. xxi. pp. 180 &c. 

 t Mem. Geol. Survey, vol. iii. plate xi. fig. 1. 

 | Coll. John Hopkinson, Esq. 



