﻿460 
  MR. 
  S. 
  S. 
  BTTCKHAX 
  OX 
  THE 
  

  

  As 
  soon 
  as 
  I 
  clearly 
  grasped 
  the 
  facts 
  concerning 
  the 
  so-called 
  

   " 
  Midford 
  Sands," 
  and 
  when 
  I 
  became 
  aware 
  of 
  certain 
  palaeonto- 
  

   logical 
  evidence 
  which 
  1 
  shall 
  have 
  to 
  mention 
  presently, 
  it 
  occurred 
  

   to 
  me 
  to 
  propose 
  that 
  the 
  " 
  Toarcien 
  " 
  should 
  be 
  a 
  separate 
  and 
  

   distinct 
  division 
  of 
  the 
  Jura-formation, 
  or, 
  if 
  it 
  he 
  preferred, 
  a 
  distinct 
  

   formation 
  of 
  the 
  Jurassic 
  system. 
  I 
  now 
  find, 
  however, 
  that 
  in 
  this 
  

   matter 
  I 
  have 
  long 
  ago 
  been 
  forestalled. 
  Eugene 
  Deslongschamps 
  

   says 
  his 
  father 
  considered 
  the 
  series 
  I 
  propose 
  to 
  call 
  " 
  Toarcien" 
  as 
  

   an 
  intermediate 
  subformation 
  of 
  very 
  distinct 
  character 
  *, 
  and 
  I 
  am 
  

   inclined 
  to 
  agree 
  with 
  this 
  opinion, 
  rather 
  than 
  include 
  these 
  strata 
  

   in 
  the 
  Inferior-Oolite 
  series 
  ; 
  because 
  there 
  exists 
  a 
  far 
  more 
  marked 
  

   stratigraphical 
  and 
  palaeontological 
  break 
  at 
  the 
  end 
  of 
  the 
  " 
  Toar- 
  

   cien 
  " 
  than 
  at 
  the 
  beginning. 
  Consequently, 
  in 
  my 
  opinion, 
  those 
  

   who 
  would 
  relegate 
  the 
  " 
  Toarcien 
  " 
  to 
  the 
  Lias 
  have 
  the 
  weight 
  of 
  

   evidence 
  upon 
  their 
  side 
  ; 
  but 
  I 
  am 
  opposed 
  to 
  this 
  view, 
  because 
  to 
  

   us, 
  in 
  England, 
  it 
  seems 
  so 
  entirely 
  misleading 
  and 
  anomalous 
  to 
  call 
  

   the 
  Murchisonce- 
  and 
  Concavum-zojxes 
  — 
  in 
  the 
  Cotteswolds 
  nearly 
  

   the 
  whole 
  Oolitic 
  escarpment 
  — 
  by 
  the 
  term 
  Lias. 
  Again, 
  there 
  is 
  

   quite 
  a 
  sufficient 
  palseontological 
  break 
  at 
  the 
  beginning 
  of 
  the 
  

   " 
  Toarcien 
  " 
  to 
  warrant 
  our 
  making 
  it 
  a 
  distinct 
  stage 
  or 
  formation 
  ; 
  

   and 
  probably 
  stratigraphical 
  evidence 
  will 
  also 
  justify 
  this 
  proceeding. 
  

   The 
  term 
  " 
  Toarcien 
  " 
  commits 
  us 
  to 
  nothing 
  like 
  the 
  term 
  " 
  Inferior 
  

   Oolite 
  ; 
  " 
  it 
  does 
  not 
  say 
  whether 
  the 
  strata 
  are 
  clay, 
  sand, 
  or 
  lime- 
  

   stone 
  ; 
  and 
  considering 
  how 
  unreliable 
  a 
  guide 
  lithology 
  is, 
  I 
  consider 
  

   this 
  a 
  very 
  important 
  point. 
  Those 
  who 
  are 
  apt 
  to 
  defend 
  the 
  

   present 
  divisions, 
  especially 
  Inferior 
  Oolite, 
  1st, 
  because 
  of 
  the 
  

   Oolitic 
  character 
  of 
  its 
  rocks, 
  composed, 
  too, 
  of 
  a 
  limestone, 
  in 
  distinc- 
  

   tion 
  to 
  the 
  clay 
  or 
  sand 
  below, 
  2nd, 
  because 
  this 
  mass 
  of 
  limestone 
  

   forms 
  such 
  an 
  important 
  and 
  well-marked 
  — 
  easily 
  recognizable 
  — 
  fea- 
  

   ture 
  in 
  the 
  country, 
  should 
  remember 
  that 
  this 
  is 
  by 
  no 
  means 
  always 
  

   the 
  case, 
  even 
  in 
  England 
  ; 
  while 
  over 
  the 
  much 
  greater 
  area 
  — 
  the 
  

   Continent 
  — 
  it 
  is 
  the 
  exception 
  ; 
  because 
  clay, 
  sand, 
  or 
  marl 
  are 
  wont 
  

   to 
  make 
  up 
  a 
  large 
  part 
  of 
  the 
  Murchisonce-zone 
  and 
  of 
  the 
  zones 
  

   below 
  it. 
  

  

  The 
  term 
  " 
  Toarcien" 
  will 
  supersede 
  a 
  number 
  of 
  names 
  which 
  

   have 
  been 
  applied 
  to 
  its 
  various 
  constituents, 
  namely, 
  Upper 
  Lias 
  

   Clay, 
  Upper 
  Lias 
  Sands, 
  Supra-liassic 
  Sands, 
  Inferior- 
  Oolite 
  Sands, 
  

   Midford 
  Sands, 
  Infra-oolitic 
  marls, 
  Lower 
  division 
  of 
  the 
  Inferior 
  

   Oolite, 
  Lower 
  Bajocien, 
  &c. 
  

  

  Prof. 
  Deslongschamps 
  (ojj. 
  cit. 
  p. 
  100, 
  footnote) 
  says 
  that 
  the 
  name 
  

   " 
  Toarcien 
  " 
  was 
  unfortunately 
  chosen, 
  because 
  at 
  Thouarsmany 
  of 
  the 
  

   beds 
  of 
  this 
  age 
  are 
  wanting 
  ; 
  in 
  Normandy 
  the 
  series 
  is 
  more 
  com- 
  

   plete, 
  but 
  thin 
  and 
  irregular 
  : 
  but 
  in 
  the 
  Moselle 
  department 
  the 
  

   strata 
  are 
  most 
  complete. 
  

  

  In 
  order 
  to 
  show 
  this, 
  he 
  appends 
  a 
  Table 
  of 
  the 
  strata 
  in 
  the 
  

   different 
  localities 
  (p. 
  101), 
  part 
  of 
  which 
  I 
  here 
  reproduce 
  (Table 
  I., 
  

   facing 
  this 
  page) 
  ; 
  but 
  as 
  the 
  strata 
  of 
  Dorset 
  are 
  certainly 
  more 
  

   developed 
  and 
  show 
  fewer 
  lacunae 
  than 
  even 
  those 
  of 
  the 
  Moselle, 
  

   I 
  place 
  them, 
  and 
  also 
  those 
  of 
  the 
  Cotteswolds, 
  side 
  by 
  side 
  with 
  

   * 
  See 
  Eugene 
  Deslongschamps. 
  op. 
  cit. 
  p. 
  98. 
  

  

  