﻿1XXX 
  PBOCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY, 
  i 
  [May 
  1 
  897, 
  

  

  which 
  I 
  classed 
  as 
  Dimetian 
  in 
  1878, 
  and 
  afterwards 
  often 
  men- 
  

   tioned 
  as 
  resembling 
  the 
  granitoid 
  and 
  massive 
  gneissose 
  rocks 
  in 
  

   the 
  North-west 
  of 
  Scotland. 
  In 
  the 
  Cambrian 
  conglomerates 
  near 
  

   Llanfaelog 
  there 
  is 
  a 
  remarkable 
  assemblage 
  of 
  fragments 
  which 
  

   gives 
  indisputable 
  evidence 
  of 
  the 
  pre-Cambrian 
  rocks 
  which 
  were 
  

   in 
  existence 
  in 
  that 
  area 
  when 
  the 
  conglomerates 
  were 
  deposited, 
  

   and 
  of 
  their 
  condition 
  when 
  the 
  fragments 
  were 
  broken 
  ofr. 
  

  

  In 
  papers 
  read 
  before 
  the 
  Society 
  in 
  1883, 
  the 
  fragments 
  con- 
  

   tained 
  in 
  these 
  conglomerates 
  were 
  described 
  by 
  Prof. 
  Bonney 
  and 
  

   myself, 
  and 
  we 
  then 
  showed 
  that 
  large 
  masses 
  of 
  the 
  granite, 
  

   gneiss, 
  volcanic 
  rocks, 
  and 
  schists, 
  such 
  as 
  are 
  now 
  seen 
  in 
  situ 
  in 
  

   the 
  neighbourhood, 
  are 
  abundant 
  in 
  them, 
  and 
  by 
  microscopic 
  

   examination 
  it 
  was 
  found 
  that 
  no 
  important 
  change 
  had 
  taken 
  place 
  

   in 
  these 
  rocks 
  since 
  pre-Cambrian 
  time. 
  Hitherto 
  no 
  remains 
  of 
  

   organisms 
  have 
  been 
  obtained 
  from 
  undoubted 
  pre-Cambrian 
  rocks 
  

   in 
  Anglesey, 
  but 
  recently 
  Mr. 
  Greenly 
  (Quart. 
  Journ. 
  Geol. 
  Soc. 
  

   vol. 
  lii. 
  1896, 
  p. 
  618) 
  has 
  referred 
  to 
  some 
  sponge-spicules 
  which 
  

   he 
  found 
  in 
  a 
  grit 
  near 
  Beaumaris 
  as 
  possibly 
  of 
  pre-Cambrian 
  

   age. 
  Upper 
  Cambrian 
  fossils 
  were 
  found 
  by 
  Prof. 
  Hughes 
  many 
  

   years 
  ago 
  in 
  rocks 
  near 
  the 
  centre 
  of 
  the 
  island, 
  which 
  until 
  then 
  

   had 
  been 
  classed 
  as 
  of 
  Caradoc 
  age 
  (Quart. 
  Journ. 
  Geol. 
  Soc. 
  

   vol. 
  xxxvi. 
  1880, 
  p. 
  237). 
  

  

  Up 
  to 
  the 
  present, 
  Middle 
  and 
  Lower 
  Cambrian 
  fossils 
  have 
  not 
  

   been 
  discovered 
  there, 
  but 
  I 
  see 
  no 
  reason 
  whatever 
  why 
  the 
  flaggy 
  

   sandstones 
  which 
  directly 
  overlie 
  the 
  conglomerates 
  near 
  Llanfaelog 
  

   and 
  along 
  the 
  western 
  border 
  of 
  the 
  granite-and-gneiss 
  axis 
  should 
  

   not 
  yield 
  Lower 
  or 
  Middle 
  Cambrian 
  fossils 
  if 
  properly 
  searched, 
  as 
  

   they 
  clearly 
  are 
  much 
  older 
  than 
  the 
  rocks 
  containing 
  the 
  Upper 
  

   Cambrian 
  fossils 
  farther 
  north. 
  

  

  Merionethshire. 
  

  

  On 
  the 
  flanks 
  of 
  the 
  Harlech 
  Mountains 
  Upper 
  and 
  Middle 
  

   Cambrian 
  fossils 
  were 
  found 
  many 
  years 
  ago 
  — 
  the 
  latter 
  soon 
  after 
  

   we 
  described 
  the 
  Menevian 
  beds 
  at 
  St. 
  David's. 
  As 
  there 
  are 
  

   in 
  the 
  Harlech 
  Mountains 
  considerable 
  thicknesses 
  of 
  sediments 
  

   underlying 
  the 
  beds 
  containing 
  the 
  Menevian 
  fossils, 
  it 
  is 
  more 
  than 
  

   likely 
  that 
  there 
  are 
  zones 
  also, 
  which 
  only 
  require 
  to 
  be 
  worked 
  

   out, 
  which 
  would 
  probably 
  contain 
  fossils 
  representing 
  the 
  Solva 
  and 
  

   Caerfai 
  groups 
  of 
  St. 
  David's, 
  as 
  the 
  lithological 
  characters 
  of 
  the 
  

   underlying 
  beds 
  are 
  remarkably 
  like 
  those 
  at 
  St. 
  David's. 
  

  

  I 
  have 
  expressed 
  the 
  opinion 
  in 
  previous 
  papers 
  that 
  there 
  are 
  

   indications 
  of 
  a 
  core 
  of 
  pre-Cambrian 
  rocks 
  in 
  these 
  mountains,. 
  

  

  