Dr. Henry Hicks — OleneUus Zone in Wales. 21 



gneiss (II.)- Here the relation between the granite and gneiss 

 becomes rather puzzling ; I have shown its details in a profile 

 (1 : 10,000) on pi. V. of the map, and described them in a paper 

 (" Ueber das Verhaltniss des Granits zum Gneiss am Gotthard ") 

 read at the 55th meeting of Deutsche Naturforscher u. Aerzte, held 

 at Eisenach, 1882. 



Weissensee, Berlin, 7 Oct., 1891. 



T 



III. — The Fauna of the Olenelltjs Zone in Wales. 

 By Henry Hicks, M.D., F.R.S., Sec.G.S. 



N his recently published excellent Memoir on the " Fauna of the 

 Lower Cambrian or Olenellus Zone," ^ Mr. Walcott has referred 

 briefly to the presence of the fauna in Wales. The following 

 additional facts bearing on the question may therefore be of some 

 interest, and they will, I think, show that there is strong evidence 

 in favour of the conclusion arrived at, that the Olenellus fauna 

 occurs in the Caerfai Group of St. Davids, and in beds at the same 

 horizon in North Wales. 



South Wales. 



In the year 1871, in a paper printed in the Q.J.G.S, vol. xxvii. 

 p. 399, I described and figured some fossils which I had discovered 

 near the base of the Lower Cambrian Eocks at St. David's. They 

 were Lingulella primceva, Discina pileolus ?, Leperditia ? Gamhrensis, 

 and " part of the head of a Trilobite from a bed at the base of the 

 purple rocks about 3000 feet below the Menevian Group " {i.e. in 

 the beds immediately following the basal Cambrian Conglomerate, 

 which rests unconformably on the Pre-Cambrian rocks). The Trilo- 

 bite (head) (fig. 18, pi. xv.) was too indistinct for identification, and 

 I refer to it now mainly to note the interesting fact that a Trilobite 

 had been discovered at that time at the very base of the Cambrian 

 at St. David's. What, however, has proved since to be of more import- 

 ance was the discovery, about the same time, in a highly cleaved 

 red slate near the same horizon, of several small fragments which 

 I recognized to be portions of a Crustacean, but which I then in- 

 correctly associated under one name in my description of Leperditia ? 

 Cambrensis. These fragments and others I have since obtained have . 

 now satisfied me that they are portions of heads of a species of OleneUus. 

 In referring to them I said that some of the specimens " show a reticu- 

 lated ornamentation." This form of ornamentation of the surface has 

 now been shown by Professor Schmidt,- Mr. Walcott, and others to be 

 characteristic of OleneUus. I am hoping that, ere long, another zone 

 may be discovered, in beds which have suffered less from cleavage, 

 and that it might be possible to give specific identifications, but at 

 present it is only possible to say that the genus does occur there, 



1 Extract from the Tenth Annual Report of the Director of the U.S. Geological 

 Survey, Washington, 1890. 



2 "Ueber eine Neueutdeckte Untercamhrische Fauna in Estland," St. Petersbourg, 



