﻿OJF 
  THE 
  BALTIC 
  PROVINCES 
  OF 
  RUSSIA. 
  517 
  

  

  Yolb., 
  Helmersonia, 
  Pand., 
  and 
  Keyserlingia, 
  Pand. 
  This 
  typical 
  

   Ungulite 
  Grit 
  attains 
  a 
  thickness 
  of 
  not 
  more 
  than 
  three 
  or 
  four 
  feet 
  ; 
  

   it 
  is 
  very 
  often 
  intercalated 
  with 
  thin 
  hands 
  of 
  the 
  strata 
  of 
  the 
  suc- 
  

   ceeding 
  stage. 
  

  

  This 
  stage 
  (3), 
  the 
  Dictyonema-slsite, 
  is 
  the 
  highest 
  member 
  of 
  our 
  

   Cambrian 
  series, 
  and 
  a 
  very 
  important 
  one 
  too. 
  as 
  it 
  is 
  the 
  only 
  in- 
  

   dubitable 
  connecting 
  link 
  between 
  our 
  Cambrian 
  and 
  that 
  of 
  Scan- 
  

   dinavia. 
  The 
  Dictyonema 
  -slate 
  has 
  a 
  thickness 
  of 
  from 
  1 
  to 
  10 
  feet, 
  

   and 
  is 
  exactly 
  identical 
  with 
  the 
  same 
  stage 
  as 
  developed 
  in 
  Sweden 
  

   and 
  Norway. 
  It 
  must 
  be 
  looked 
  upon 
  as 
  a 
  direct 
  continuation 
  of 
  the 
  

   Swedish 
  Dictyonema-slsite, 
  its 
  petrological 
  character 
  being 
  the 
  same. 
  

   The 
  characteristic 
  species, 
  Dictyonema 
  flab 
  ellif 
  or 
  me, 
  Eichw., 
  of 
  the 
  beds 
  

   in 
  both 
  countries 
  is 
  the 
  same 
  ; 
  and, 
  moreover, 
  the 
  geological 
  position, 
  

   as 
  shown 
  by 
  the 
  succeeding 
  stages 
  of 
  the 
  Glauconitic 
  and 
  Orthoceratite 
  

   Limestone, 
  is 
  correspondent. 
  As 
  the 
  Dictyonema-sL&te 
  in 
  Sweden 
  is 
  

   intimately 
  connected 
  with 
  the 
  Olenus-heds, 
  and, 
  with 
  us, 
  with 
  the 
  

   Ungnlite-beds, 
  the 
  latter 
  may 
  possibly 
  be 
  regarded 
  as 
  a 
  coast-facies 
  

   of 
  the 
  Olenus-st&ge 
  of 
  the 
  Swedish 
  Cambrian. 
  The 
  lower 
  sands 
  and 
  

   the 
  Blue 
  Clay 
  must 
  consequently 
  also 
  correspond 
  to 
  some 
  part 
  of 
  

   the 
  Swedish 
  Cambrian 
  ; 
  yet 
  it 
  is 
  difficult 
  to 
  say 
  to 
  which 
  of 
  them, 
  

   identical 
  fossils 
  being 
  altogether 
  wanting. 
  The 
  lithological 
  cha- 
  

   racter 
  of 
  the 
  lowest 
  sandstone 
  (near 
  to 
  the 
  Blue 
  Clay) 
  reminded 
  

   Dr. 
  Linnarsson 
  of 
  some 
  beds 
  of 
  the 
  Swedish 
  ifop%£on-sandstone, 
  

   Annelide-tracks 
  and 
  Cruziana, 
  as 
  in 
  W. 
  Gothland, 
  being 
  also 
  visible 
  

   with 
  us. 
  The 
  Dictyonema-sl&te 
  in 
  some 
  places 
  shows, 
  besides 
  

   the 
  Dictyonema, 
  also 
  some 
  Graptolites 
  (my 
  memoir, 
  p. 
  16, 
  fig. 
  4). 
  

   These 
  I 
  believe 
  to 
  be 
  identical 
  with 
  Bryograptus 
  Kjerulfi, 
  Lapw., 
  as 
  

   figured 
  by 
  Kjerulf 
  in 
  his 
  Yeiviser 
  ved 
  geologiske 
  Excursioner 
  i 
  

   Christiania 
  omegn, 
  p. 
  3, 
  fig. 
  6. 
  

  

  In 
  England 
  the 
  Dictyonema-be&s 
  have 
  a 
  corresponding 
  position 
  at 
  

   the 
  top 
  of 
  the 
  Cambrian 
  (in 
  the 
  sense 
  of 
  Hicks 
  and 
  Lapworth) 
  in 
  

   the 
  lower 
  Tremadoc 
  (cf. 
  Lapworth 
  in 
  the 
  Geol. 
  Mag. 
  1881, 
  p. 
  320) 
  ; 
  

   yet 
  the 
  identity 
  of 
  Dictyonema 
  socials, 
  Salt., 
  with 
  D. 
  flabelliforme, 
  

   Eichw., 
  though 
  asserted 
  by 
  Tornqvist, 
  is 
  not, 
  in 
  my 
  opinion, 
  fully 
  

   decided. 
  The 
  Norwegian 
  D. 
  norvegicum 
  and 
  D. 
  graptolithinum 
  of 
  

   Kjerulf 
  are, 
  as 
  asserted 
  by 
  Brogger, 
  exactly 
  the 
  same 
  as 
  our 
  D. 
  flabel- 
  

   liforme. 
  

  

  To 
  complete 
  the 
  account 
  of 
  our 
  Cambrian 
  strata, 
  we 
  may 
  admit 
  

   that 
  the 
  development 
  of 
  the 
  Cambrian 
  system 
  or 
  division 
  is 
  not 
  

   typical 
  with 
  us 
  ; 
  yet 
  the 
  strata 
  of 
  these 
  stages 
  cannot 
  be 
  compared 
  

   to 
  any 
  excepting 
  those 
  of 
  the 
  Cambrian 
  stages 
  of 
  other 
  Palaeozoic 
  

   countries, 
  and 
  therefore 
  they 
  must 
  be 
  regarded 
  as 
  representing 
  the 
  

   Cambrian 
  or 
  Primordial 
  Silurian 
  with 
  us. 
  

  

  Lower 
  Silurian 
  Strata 
  (Ordovici'an, 
  Lapw.). 
  

  

  The 
  Lower 
  Silurian 
  (Ordovician, 
  Lapw.) 
  is 
  the 
  richest 
  among 
  our 
  

   divisions. 
  Nowhere 
  else, 
  I 
  believe, 
  has 
  such 
  a 
  regular 
  undisturbed 
  

   development 
  obtained 
  of 
  this 
  part 
  of 
  the 
  Palaeozoic 
  formations. 
  In 
  

   other 
  countries 
  there 
  are 
  several 
  breaks, 
  caused 
  by 
  interchange 
  of 
  

  

  