﻿326 
  J. 
  E. 
  MARR 
  ON 
  THE 
  CAMBRIAN 
  AND 
  

  

  in 
  fact, 
  instead 
  of 
  running 
  in 
  a 
  N.N.W. 
  and 
  E.S.E. 
  direction, 
  seems 
  

   to 
  have 
  run 
  more 
  W.S.W. 
  and 
  E.N.E. 
  ; 
  for 
  we 
  find 
  many 
  shallow- 
  

   water 
  deposits 
  in 
  Britain 
  at 
  this 
  period, 
  but 
  deep 
  ones 
  in 
  the 
  central 
  

   Swedish 
  areas. 
  The 
  May-Hill 
  fauna, 
  as 
  it 
  occurs 
  in 
  Wales, 
  seems 
  

   to 
  have 
  spread 
  as 
  far 
  as 
  Christiania 
  and 
  "Westrogothia 
  (Brachiopod- 
  

   beds) 
  in 
  May-Hill 
  times, 
  but 
  to 
  have 
  been 
  there 
  stopped 
  by 
  deep- 
  

   water 
  from 
  reaching 
  Dalecarlia, 
  where 
  the 
  Lobiferus-beds 
  occur. 
  

   Deep 
  water 
  prevailed 
  also 
  in 
  this 
  area 
  during 
  the 
  accumulation 
  of 
  

   the 
  succeeding 
  Retiolites-beds 
  ; 
  but 
  the 
  overlying 
  Leptoena-limestone 
  

   has 
  a 
  decided 
  admixture 
  of 
  May-Hill 
  forms 
  such 
  as 
  Sphcereooochus 
  

   angustifrons, 
  Remopleurides, 
  Meristella 
  crassa, 
  Stricklandinia, 
  

   Orihisina 
  adscendens, 
  Leptcena 
  quinquecostata, 
  Macrochilia, 
  &c. 
  

   (cf. 
  Tornqvist, 
  Of 
  v. 
  af 
  Kongl. 
  Vet.-Akad. 
  Eorh. 
  1879, 
  no. 
  2, 
  p. 
  76) 
  ; 
  

   so 
  that 
  one 
  would 
  expect 
  to 
  find 
  shallow- 
  water 
  deposits 
  of 
  Eetiolites- 
  

   shale 
  age 
  further 
  north 
  than 
  Dalecarlia, 
  in 
  order 
  to 
  allow 
  of 
  the 
  

   migration 
  into 
  Dalecarlia 
  of 
  these 
  forms. 
  Such 
  shallow-water 
  de- 
  

   posits 
  occur 
  in 
  Jemtland 
  (Linnarsson, 
  Geol. 
  Eor. 
  i 
  Stockh. 
  Eorh. 
  

   1879). 
  Mingled 
  with 
  the 
  forms 
  enumerated 
  are 
  others 
  which 
  seem 
  

   to 
  have 
  come 
  from 
  Russia, 
  as 
  Illamus 
  Volborthi, 
  and 
  others, 
  again, 
  

   of 
  characteristic 
  Wenlock 
  type, 
  which 
  may 
  have 
  migrated 
  from 
  the 
  

   Gothland 
  area. 
  Besides 
  these, 
  there 
  are 
  several 
  forms 
  (such 
  as 
  

   Isocolus 
  Sjbgreni) 
  which 
  are 
  peculiar 
  to 
  the 
  bed. 
  This 
  explanation 
  

   of 
  the 
  occurrence 
  of 
  May-Hill 
  forms 
  in 
  the 
  Leptaena-limestone 
  

   obviates 
  all 
  the 
  difficulties 
  which 
  have 
  been 
  raised 
  concerning 
  its 
  

   age. 
  

  

  § 
  5. 
  Summary. 
  

  

  The 
  classification 
  of 
  Prof. 
  Sedgwick 
  is 
  quite 
  applicable 
  to 
  the 
  

   older 
  palaeozoic 
  rocks 
  of 
  Sweden. 
  

  

  The 
  boundary 
  at 
  the 
  base 
  of 
  the 
  equivalents 
  of 
  the 
  May 
  -Hill 
  beds 
  

   is 
  marked 
  by 
  three 
  distinct 
  kinds 
  of 
  events 
  : 
  first, 
  there 
  is 
  a 
  physical 
  

   break, 
  as 
  indicated 
  by 
  the 
  absence 
  of 
  several 
  beds 
  at 
  the 
  summit 
  of 
  

   the 
  Cambrian 
  in 
  various 
  localities, 
  and 
  by 
  the 
  occurrence 
  of 
  conglo- 
  

   meratic 
  beds 
  at 
  the 
  base 
  of 
  the 
  Silurian, 
  resting 
  unevenly 
  upon 
  the 
  

   older 
  deposits 
  ; 
  secondly, 
  there 
  is 
  a 
  palaeontological 
  break, 
  which 
  is 
  

   more 
  especially 
  marked 
  in 
  the 
  case 
  of 
  the 
  deep-water 
  beds 
  ; 
  for 
  

   although 
  the 
  various 
  deep-water 
  beds 
  of 
  Cambrian 
  times 
  have 
  often 
  

   species 
  in 
  common, 
  or 
  closely 
  allied 
  representative 
  species, 
  as 
  have 
  

   those 
  of 
  the 
  Silurian 
  also, 
  there 
  are 
  very 
  few 
  common 
  to 
  the 
  two 
  

   systems 
  ; 
  thirdly, 
  the 
  trend 
  of 
  the 
  coast-line 
  in 
  early 
  Silurian 
  times 
  

   seems 
  to 
  have 
  been 
  totally 
  different 
  from 
  that 
  which 
  existed 
  in 
  late 
  

   Cambrian 
  times, 
  thus 
  giving 
  rise 
  to 
  a 
  considerable 
  difference 
  in 
  the 
  

   direction 
  of 
  migration 
  of 
  the 
  shallow-water 
  faunas 
  of 
  the 
  two 
  

  

  Is 
  there 
  any 
  other 
  break 
  of 
  equal 
  importance 
  to 
  this 
  one 
  in 
  

   Scandinavia 
  ? 
  Several 
  authors 
  have 
  drawn 
  a 
  boundary 
  at 
  the 
  base 
  

   of 
  the 
  Ceratopyge-limestone, 
  on 
  palaeontological 
  grounds 
  : 
  there 
  is 
  

   no 
  physical 
  break 
  there 
  ; 
  and 
  the 
  value 
  of 
  the 
  palaeontological 
  break 
  

   may 
  be 
  estimated 
  from 
  the 
  following 
  remark 
  of 
  Dr. 
  Tornqvist 
  (Ofv. 
  

   af 
  K. 
  Yet.-Akad. 
  Forh. 
  1879, 
  no. 
  2, 
  p. 
  66) 
  : 
  — 
  " 
  In 
  Scandinavia 
  

  

  