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  PROF. 
  F. 
  SCHMIDT 
  ON 
  THE 
  SILURIAN 
  STRATA 
  

  

  C 
  3, 
  Itfer 
  Beds. 
  

  

  The 
  stage 
  C 
  3 
  I 
  have 
  distinguished 
  only 
  at 
  a 
  few 
  localities, 
  prin- 
  

   cipally 
  at 
  Itfer, 
  north 
  of 
  Wesenberg 
  in 
  Esthonia. 
  The 
  fauna 
  is 
  

   nearly 
  the 
  same 
  as 
  in 
  C 
  2, 
  but 
  there 
  are 
  found 
  some 
  peculiar 
  Tri- 
  

   lobites, 
  as 
  Splicer 
  ocori/phe 
  Huebneri, 
  mihi, 
  and 
  Chasmops 
  Wrangeli, 
  

   mihi. 
  Besides 
  these, 
  some 
  forms 
  belonging 
  to 
  the 
  stage 
  D, 
  for 
  instance 
  

   Mastopora 
  concava, 
  Eichw., 
  begin 
  to 
  appear. 
  It 
  is 
  an 
  intermediate 
  

   stage 
  of 
  about 
  20-30 
  feet 
  in 
  thickness, 
  and 
  consists 
  of 
  a 
  hard 
  lime- 
  

   stone 
  with 
  siliceous 
  concretions, 
  like 
  the 
  lower 
  strata 
  of 
  stage 
  D. 
  

  

  Stage 
  D, 
  or 
  Jewe 
  Zone. 
  

  

  The 
  stage 
  D, 
  or 
  the 
  Jewe 
  zone, 
  is 
  very 
  characteristic 
  of 
  our 
  

   Silurian 
  system 
  : 
  it 
  can 
  be 
  traced 
  on 
  the 
  map 
  from 
  Gatschina 
  (south 
  

   of 
  St. 
  Petersburg) 
  as 
  far 
  as 
  Spitham 
  at 
  the 
  north-western 
  angle 
  of 
  

   Esthonia. 
  In 
  the 
  western 
  part 
  of 
  our 
  Silurian 
  I 
  have 
  been 
  able 
  to 
  

   distinguish 
  two 
  subdivisions, 
  the 
  Jewe 
  zone 
  and 
  the 
  Kegel 
  zone 
  ; 
  

   but 
  in 
  the 
  east, 
  in 
  the 
  Government 
  of 
  St. 
  Petersburg 
  (principally 
  

   along 
  the 
  Baltic 
  railroad), 
  I 
  could 
  see 
  only 
  the 
  uppermost. 
  Both 
  

   subdivisions 
  together 
  may 
  reach 
  a 
  thickness 
  of 
  perhaps 
  100 
  feet, 
  

   principally 
  in 
  the 
  east, 
  where, 
  at 
  the 
  railroad-station 
  Jelisawetino, 
  

   an 
  artesian 
  well, 
  beginning 
  in 
  the 
  upper 
  part 
  of 
  D, 
  did 
  not 
  strike 
  the 
  

   Glauconite 
  Limestone, 
  B 
  2, 
  even 
  at 
  a 
  depth 
  of 
  200 
  feet. 
  

  

  The 
  lower 
  part 
  of 
  the 
  stage 
  D 
  (the 
  true 
  Jewe 
  zone) 
  consists 
  

   of 
  siliceous 
  marly 
  limestone, 
  the 
  shells 
  of 
  fossils 
  being 
  very 
  often 
  

   silicified. 
  Some 
  fossils 
  of 
  the 
  underlying 
  stage 
  C 
  still 
  occur, 
  e. 
  g. 
  

   Echinosph&rites 
  aurantium, 
  Orthisina 
  ScJimidti, 
  Pahlen, 
  Orthoceras 
  

   vertebrale, 
  Eichw. 
  But 
  the 
  leading 
  fossils 
  are 
  Cheirurus 
  pseudo- 
  

   hemicrccnium, 
  Nieszk., 
  Hemicosmites 
  extraneus, 
  Eichw., 
  Mastopora 
  

   concava, 
  Eichw., 
  and 
  various 
  conical 
  casts 
  (my 
  memoir 
  p. 
  33, 
  fig. 
  6), 
  

   undoubtedly 
  of 
  organic 
  origin, 
  but 
  not 
  yet 
  clearly 
  interpreted. 
  The 
  

   upper 
  stage 
  of 
  D 
  (the 
  Kegel 
  zone) 
  is 
  more 
  marly 
  (not 
  siliceous), 
  and 
  

   is 
  very 
  rich 
  in 
  fossils, 
  for 
  example 
  : 
  — 
  Lichas 
  defiecca, 
  Ang., 
  L. 
  illce- 
  

   noides, 
  Nieszk., 
  Chasmops 
  bucculenta, 
  Sjogr., 
  Strophomena 
  Asmusi, 
  

   Vera., 
  Orthisina 
  anomala, 
  Schloth., 
  Cyclocrinites 
  Spasslcii, 
  Eichw., 
  

   &c. 
  Both 
  stages 
  together 
  are 
  very 
  rich 
  in 
  Chasmops 
  (6 
  sp.), 
  and 
  

   have 
  a 
  great 
  variety 
  of 
  Bellerophons 
  and 
  Lamellibranchiata. 
  The 
  

   fauna 
  of 
  the 
  stage 
  J) 
  has 
  not 
  yet 
  been 
  well 
  studied. 
  In 
  Scandina- 
  

   via 
  and 
  the 
  British 
  Islands, 
  as 
  well 
  as 
  in 
  North 
  America, 
  no 
  une- 
  

   quivocal 
  representatives 
  of 
  our 
  stage 
  are 
  found 
  ; 
  yet 
  the 
  Trinucleus- 
  

   schists 
  of 
  Sweden 
  may 
  probably 
  be 
  regarded 
  as 
  such. 
  At 
  the 
  

   bottom 
  of 
  the 
  Baltic 
  sea, 
  however, 
  the 
  Jewe 
  zone 
  may 
  spread 
  much 
  

   further 
  west, 
  as 
  in 
  the 
  island 
  of 
  Oeland 
  and 
  in 
  the 
  plains 
  of 
  North 
  

   Germany 
  many 
  fossils 
  belonging 
  to 
  this 
  stage 
  have 
  been 
  found 
  in 
  

   the 
  Drift-deposits. 
  

  

  Stage 
  E, 
  or 
  Wesenberg 
  Zone. 
  

  

  The 
  next 
  zone 
  E, 
  the 
  Wesenberg 
  zone, 
  begins 
  on 
  the 
  east 
  of 
  the 
  

   Narowa 
  river 
  at 
  the 
  river 
  Pljussa, 
  and 
  can 
  be 
  traced 
  west 
  through 
  

   the 
  whole 
  of 
  Esthonia 
  in 
  a 
  direction 
  parallel 
  to 
  the 
  Jewe 
  zone. 
  This 
  

  

  