Geologists'' Association. 45 



In this communication the author gave descriptions of all the 

 fossils hitherto undescribed from the Menevian rocks of Wales. The 

 additions made to the fauna of the Lower Cambrian rocks (Long- 

 mynd and Menevian groups) by the author's researches in Wales 

 during the last few years now number about fifty species, belonging 

 to twenty-two genera, as follows : — 



Trilobites, 10 genera and 30 species. 



Bivalved and other Crustaceans, 3 genera and 4 species. 



Brachiopods, 4 genera and 6 species. 



Pteropods, 3 genera and 6 species. 



Sponges, 1 genus and 4 species. 



Cystideans, 1 genus and 1 species. 

 By adding to these the Annelids, which are plentiful also in these 

 rocks, we get seven great groups represented in this fauna, the 

 earliest known at present in this country. By referring to the 

 Tables published in M. BaiTande's excellent new work on Trilobites, 

 it will be seen that this country also has produced a great variety, 

 or, rather, representatives of a greater number of groups from these 

 early rocks than any other coimtry. The species described included 

 Agnostus, 5 species ; Arionellus, 1 species ; Erinnys, 1 species ; 

 HolocepJialina, 1 species ; ConocorypJie, 2 species ; Anopolenus, 2 

 species ; Cyrtotheca, 1 species ; StenotJieca, 1 species ; Theca, 2 

 species ; JProtocysfites, 1 species, etc. The author also entered into 

 a consideration of the range of the genera and species in these early 

 rocks, and showed that, with the exception of the BracMopods, 

 Sponges, and the smaller Crustacea, the range was very limited. 



A description of the various beds forming the Cambrian rocks of 

 St. David's was also given, and proofs adduced to show that frequent 

 oscillations of the sea-bottom took place at this early period, and 

 that the barrenness of some portions of the strata, and the richness 

 of other parts, were mainly attributable to these frequent changes. 



DiscL'ssioN. — Mr. Gwyn Jeffreys siiggested that the term Polyzoa might be 

 adopted in preference to that of Bryozoa, as being the more ancient term, and that 

 the name Proserpina should not be applied to the new genus of Trilobites, as it had 

 already been appropriated to a tropical form of land-sheU. 



Mr. Hicks thanked Mr. Jeifreys for his suggestions, which he was inclined to 

 adopt. 



Geologists' Association. — 1st December, 1871, — The Eev. T. 

 Wiltshire, M.A., F.G.S., President, in the Chair. The following 

 paper was read : " On the Glacial Drifts of North London." By 

 Henry Walker, Esq. — These drifts were described under the classi- 

 fication and nomenclature given to the Glacial deposits by Mr. Searles 

 V. Wood, jun. They were traced from East End (Highgate) and 

 Muswell Hill to Finchley, Colney Hatch Lane, and Whetstone. 

 The profusion of chalk found in the Glacial clay at these jDlaces 

 bears out the designation of the main dejjosit in South-eastern 

 England as the great Clialky Boulder-clay ; but it is also found that 

 the sands and gravels of the Middle Glacial, which Mr. Wood seems 

 to restrict to a much lower horizon than Finchley, are also to be 

 found at these localities. At Whetstone the Chalky Boulder-clay is 



