142 



PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



made, and also the care bestowed upon the stratigraphical grouping 

 of the fossils. The Upper Bala group of Sedgwick includes the 

 Aher-Hirnant Limestone, which occurs above the Bala Limestone, 

 also the lower part of the Coniston Mags, the beds above the Bala 

 Limestone, and below the May-Hill Sandstone ; it therefore includes 

 the Lower Llandovery or Mathyraful Limestone near Meifod, and 

 also the rich fossiliferous series at Haverfordwest, the Dalquorhan 

 and Mulloch beds of Scotland, and the laume and Cong beds of 

 Galway *. The Woodwardian Catalogue enumerates 43 genera and 

 100 species from this group (the Lower Llandovery of the Geolo- 

 gical Survey), 18 genera and 36 species of which also occur in the 

 Middle Bala below. 



Lower Llandovery. 



In my analysis of the Lower Llandovery species from the rocks 

 of that age in North and South Wales, Scotland, and Ireland, I have 

 brought together and tabulated all that is known relative to the 

 range and distribution of life through this Middle Silurian or Upper 

 Bala group of Sedgwick. The table shows the value of this upper 

 member of the Caradoc or Bala beds, and its relation to the transi- 

 tional Upper Llandovery, or the group so called, which stands be- 

 tween and connects the Lower Silurian of the Survey with the well- 

 defined succeeding Wenlock and Ludlow series. Careful analysis of 

 the species in both their stratigraphical and geographical distri- 

 bution shows how small a specifically characterized group the Lower 

 Llandovery appears to be, for only 115 species out of 204 are really 

 Lower Llandovery. The total number of genera and species known 

 for all Britain is 68 genera and 204 species ; but 50 genera and 

 104 of these species transgressed or came from the Caradoc and Bala 

 beds below, thus reducing the actual Llandovery fauna to 18 genera 

 and 100 species. The intimate connexion with the Upper Llan- 

 dovery is chiefly through the Actinozoa (20 species), Brachiopoda 

 (38), Crustacea (10), and Gasteropoda (8). No form of Protozoa, 

 Echinodermata, or Pteropoda is common to the two Llandoveries 

 in any area in Britain. 



No species of Echinodermata occurs in North "Wales, Ireland, or 

 Westmoreland. No Lower Llandovery Annelid is known in North 

 Wales. Neither do we know of any Lamellibranch, Pteropod, 

 Heteropod, or Cephalopod in the same area. I will now discuss 

 through tabular analysis the distribution of the chief zoological 

 groups in the Lower Llandovery, viz. the Echinodermata, the Crus- 

 tacea, Brachiopoda, and Gasteropoda. The remaining 7 of the 13 

 groups (there being no plants) are conspicuous through feeble re- 

 presentation, due doubtless to geographical changes towards the 

 close of the Caradoc and Bala period. 



Hydrozoa. — The careful researches and generalizations of Lin- 

 narsson in Sweden, Lapworth, Nicholson, Carruthers, and Hopkin- 



* Vide Cat. Coll. Cambrian and Silurian Fossils in Mus. Univ. of Cambridge, 

 pp. 25, 26, 39, & 72, for greater details. 



