﻿524 
  PROF. 
  F. 
  SCHMIDT 
  ON 
  THE 
  SILURIAN" 
  STRATA 
  

  

  good 
  many 
  Encrinites 
  ; 
  but 
  the 
  species 
  are 
  for 
  the 
  most 
  part 
  not 
  yet 
  

   defined. 
  The 
  Trilobites 
  are 
  restricted 
  in 
  number, 
  and 
  by 
  no 
  means 
  

   so 
  numerous 
  as 
  in 
  the 
  stages 
  JB 
  and 
  C. 
  Several 
  genera 
  aud 
  sub- 
  

   genera 
  have 
  their 
  last 
  representatives 
  in 
  this 
  stage, 
  such 
  as 
  Asaphus, 
  

   Cybele, 
  Chasmops, 
  Pseudosphcerexochus, 
  and 
  others. 
  

  

  This 
  stage 
  is 
  very 
  well 
  represented 
  in 
  other 
  Silurian 
  countries, 
  

   in 
  Sweden 
  by 
  the 
  Z<?ptae»a-limestone 
  of 
  Dalarne 
  ; 
  in 
  Norway 
  by 
  

   the 
  Gasteropod-limestone 
  (Brogger) 
  of 
  Porsgrund 
  and 
  Brewig 
  ; 
  in 
  

   Britain 
  by 
  the 
  Caradoc 
  sandstone, 
  and 
  the 
  Coniston 
  and 
  Craighead 
  

   limestones 
  ; 
  in 
  America 
  by 
  the 
  Trenton 
  and 
  Hudson 
  groups. 
  The 
  

   Swedish 
  Leptcena-\\mQstove 
  at 
  the 
  Osmundsberg 
  in 
  Dalarne 
  (I 
  visited 
  

   that 
  locality) 
  seems 
  to 
  me 
  perfectly 
  identical 
  with 
  our 
  white 
  Borkholm 
  

   limestone 
  : 
  and 
  I 
  must 
  regard 
  it 
  as 
  formed 
  at 
  the 
  same 
  time 
  in 
  the 
  

   same 
  ocean. 
  The 
  following 
  list 
  of 
  identical 
  fossils 
  may 
  possibly 
  prove 
  

   the 
  correctness 
  of 
  my 
  opinion 
  : 
  — 
  Cheirurus 
  (Pseudosphcerexochus) 
  

   conformis, 
  Ang., 
  Sphcerexochus 
  angustifrons, 
  Ang., 
  Cybele 
  brevicauda, 
  

   Ang., 
  Heir 
  pes 
  Wegelini, 
  Ang., 
  Bronteus 
  laticauda, 
  Ang., 
  Primitia 
  

   brachynotha, 
  mihi, 
  Orthoceras 
  fenestratum, 
  Eichw. 
  (funiforme, 
  Ang 
  ; 
  ), 
  

   Leptcena 
  Schmidti, 
  TOrnq., 
  L. 
  luna, 
  Tornq., 
  Discina 
  gibba, 
  Lindstr., 
  

   Propora 
  conferta, 
  E. 
  & 
  H., 
  Heliolites 
  duhius, 
  mihi, 
  Syringophyllum 
  

   organon, 
  Linn., 
  and 
  many 
  others. 
  I 
  cannot 
  agree 
  with 
  some 
  of 
  the 
  

   Swedish 
  geologists 
  and 
  with 
  Prof. 
  Lapworth 
  in 
  regarding 
  the 
  Leptcena- 
  

   limestone 
  as 
  Upper 
  Silurian, 
  because 
  of 
  its 
  association 
  (the 
  stratigra- 
  

   phical 
  conditions 
  are 
  not 
  quite 
  clear 
  yet, 
  according 
  to 
  Tornqvist) 
  with 
  

   the 
  Retiolites- 
  and 
  Lobiferu 
  s-schists, 
  which 
  are 
  said 
  to 
  correspond 
  

   to 
  British 
  strata 
  of 
  Upper 
  Silurian 
  ago. 
  Of 
  the 
  British 
  Bala 
  group 
  

   I 
  may 
  mention 
  the 
  following 
  identical 
  or 
  nearly 
  allied 
  species 
  in 
  

   our 
  stage 
  F: 
  — 
  Phacops 
  (Chasmops) 
  macroura, 
  Salt., 
  not 
  Sjdgr. 
  (the 
  

   Cat's-head 
  Trilobite), 
  very 
  near 
  to 
  our 
  T. 
  Eichwaldi, 
  mihi, 
  Cheirurus 
  

   octolobatus, 
  M'Coy, 
  allied 
  to 
  our 
  C. 
  conformis, 
  Ang., 
  Encrinurus 
  

   midtisegmentatus, 
  Portl., 
  Splicer 
  'exoclms 
  angustifrons, 
  Ang. 
  (according 
  

   to 
  Tornqvist), 
  Calymene 
  senaria, 
  Conr., 
  Bellerophon 
  bilobatus, 
  Sow., 
  

   Pleiirorliynchvs 
  cf. 
  dipterus, 
  Salt., 
  Strophomena 
  eccpansa, 
  Sow., 
  

   Orthis 
  vespertilio, 
  Sow., 
  0. 
  insidaris, 
  Eichw., 
  0. 
  fissicostnta, 
  M'Coy, 
  

   0. 
  porcata, 
  M'Coy 
  (Solaris, 
  v. 
  Buch), 
  0. 
  Actonice, 
  Sow. 
  (Oswaldi, 
  v. 
  

   Buch), 
  &c. 
  The 
  corals 
  and 
  some 
  other 
  classes 
  are 
  not 
  yet 
  accurately 
  

   compared. 
  The 
  Norwegian 
  black 
  limestones 
  mentioned 
  before 
  show 
  

   a 
  still 
  greater 
  affinity, 
  for 
  instance, 
  in 
  the 
  large 
  Gasteropoda 
  Bolopea 
  

   ampidlacea, 
  Eichw., 
  Subidites 
  gigas, 
  Eichw., 
  Murchisonia 
  bellicincta, 
  

   Hall, 
  and 
  others. 
  Prof. 
  Brogger, 
  I 
  hope, 
  will 
  soon 
  give 
  us 
  a 
  de- 
  

   tailed 
  account 
  of 
  the 
  Norwegian 
  Lower 
  Silurian 
  as 
  compared 
  with 
  

   the 
  Russian, 
  as 
  in 
  1880 
  he 
  visited 
  our 
  country 
  and 
  collected 
  suffi- 
  

   cient 
  materials 
  for 
  that 
  purpose. 
  The 
  Trenton 
  and 
  Hudson 
  groups 
  

   of 
  America 
  show 
  also 
  a 
  very 
  similar 
  character 
  in 
  their 
  fauna 
  ; 
  and 
  a 
  

   more 
  detailed 
  explanation 
  of 
  the 
  fossils 
  of 
  our 
  stage 
  F 
  will 
  enable 
  

   us 
  also 
  to 
  make 
  a 
  more 
  detailed 
  parallelization 
  with 
  the 
  corresponding 
  

   American 
  strata. 
  

  

  Upper 
  Silurian 
  (Silurian, 
  Sedgw.). 
  

   Our 
  Upper 
  Silurian 
  (Silurian, 
  Sedgiv.) 
  is 
  very 
  distinctly 
  separated 
  

  

  