﻿I06 
  PROCEEDINGS 
  OP 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  racteristic, 
  are 
  absent 
  in 
  that 
  portion 
  in 
  another, 
  and 
  may 
  characterize 
  

   instead 
  either 
  a 
  higher 
  or 
  lower 
  zone. 
  

  

  Thus, 
  as 
  stated 
  by 
  the 
  author, 
  the 
  well-known 
  " 
  Exoyyra 
  virgula 
  

   in 
  the 
  Jura 
  bernois 
  and 
  elsewhere 
  is 
  characteristic 
  of 
  the 
  upper 
  

   portion 
  ; 
  at 
  the 
  Cap 
  de 
  la 
  Heve 
  [Dept. 
  Seine-Inf 
  ., 
  N.W. 
  of 
  Havre] 
  

   it 
  occurs 
  throughout; 
  and 
  in 
  England 
  it 
  is 
  wanting 
  only 
  in 
  the 
  

   upper 
  part, 
  or 
  sometimes, 
  as 
  in 
  Lincolnshire, 
  appears 
  to 
  be 
  absent 
  

   entirely." 
  So, 
  again, 
  the 
  still 
  better-known 
  or 
  more 
  conspicuous 
  

   " 
  Rhynclionella 
  inconstans, 
  which 
  is 
  the 
  characteristic 
  species 
  of 
  the 
  

   lowest 
  beds 
  in 
  England, 
  in 
  the 
  environs 
  of 
  Montbeliard 
  is 
  found 
  in 
  

   all 
  but 
  the 
  lowest, 
  and 
  most 
  frequently 
  at 
  the 
  top, 
  and 
  has 
  not 
  been 
  

   met 
  with 
  in 
  the 
  sub-Wealden 
  boring," 
  although 
  it 
  was 
  believed, 
  

   through 
  other 
  fossils, 
  that 
  we 
  were 
  near 
  the 
  base. 
  Mr. 
  Blake 
  there- 
  

   fore 
  suggests 
  that 
  " 
  on 
  account 
  of 
  this 
  peculiarity 
  of 
  the 
  distribution 
  

   of 
  the 
  Kimmeridgian 
  fossils, 
  it 
  is 
  better 
  to 
  use 
  the 
  more 
  general 
  terms 
  

   Lower, 
  Middle, 
  and 
  Upper." 
  

  

  The 
  chief 
  object 
  of 
  Mr. 
  Blake's 
  paper 
  is 
  to 
  show 
  into 
  what 
  

   palseontological 
  and 
  lithological 
  subdivisions 
  the 
  Kimmeridge 
  Clay 
  

   may 
  be 
  naturally 
  separated 
  through 
  a 
  study 
  of 
  its 
  features 
  in 
  the 
  

   field. 
  Mr. 
  Blake 
  shows 
  that 
  there 
  are 
  only 
  two 
  divisions 
  or 
  sets 
  of 
  

   beds 
  which 
  are 
  sufficiently 
  distinct 
  to 
  justify 
  their 
  separation 
  under 
  

   different 
  titles. 
  The 
  upper 
  division, 
  " 
  Yirgulian," 
  agrees 
  with 
  that 
  

   of 
  Dr. 
  Waagen 
  ; 
  but 
  our 
  lower 
  includes 
  his 
  middle 
  region 
  and 
  

   part 
  of 
  his 
  lower 
  ; 
  " 
  while 
  the 
  remaining 
  part 
  of 
  his 
  lower 
  region, 
  

   and 
  possibly 
  part 
  of 
  his 
  zone 
  of 
  Cidarisflorigemma, 
  constitute 
  a 
  series 
  

   of 
  beds 
  which, 
  from 
  their 
  containing 
  as 
  much 
  of 
  a 
  Corallian 
  as 
  a 
  

   Kimmeridgian 
  fauna," 
  Mr. 
  Blake 
  designates 
  the 
  "Kimmeridge 
  

   Passage-beds" 
  (loc.cit. 
  p. 
  197). 
  

  

  Mr. 
  Blake's 
  paper 
  therefore 
  embraces 
  the 
  history 
  of 
  the 
  Kim- 
  

   meridge 
  Clay 
  through 
  three 
  divisions 
  — 
  

  

  1. 
  The 
  Upper 
  Kimmeridge, 
  

  

  2. 
  The 
  Lower 
  Kimmeridge, 
  and 
  

  

  3. 
  The 
  Kimmeridge 
  Passage-beds. 
  

  

  The 
  Ur-PER. 
  Kimmeridge 
  Clay 
  (Yirgulien 
  of 
  foreign 
  authors) 
  

   differs 
  essentially 
  both 
  lithologically 
  and 
  palseontologically 
  from 
  the 
  

   zones 
  below. 
  This 
  division 
  is 
  developed 
  in 
  Lincolnshire 
  and 
  Dorset- 
  

   shire 
  ; 
  and 
  in 
  it 
  exclusively 
  occur 
  the 
  bituminous 
  shales, 
  paper 
  shales, 
  

   and 
  cement 
  stones. 
  These 
  beds 
  contain 
  but 
  few 
  species, 
  but 
  an 
  infinity 
  

   of 
  individuals. 
  Compressed 
  Ammonites, 
  Discina 
  latissima 
  and 
  

   Lucina 
  minuscula, 
  cover 
  the 
  leaf-like 
  planes 
  of 
  deposition. 
  Mr. 
  Blake 
  

   appends 
  a 
  complete 
  and 
  measured 
  section 
  of 
  the 
  thickness 
  of 
  the 
  

   Kimmeridge-clay 
  beds 
  at 
  Kimmeridge 
  Bay, 
  where 
  they 
  are 
  exhibited 
  

   to 
  the 
  extent 
  of 
  650 
  feet, 
  probably 
  the 
  maximum 
  in 
  any 
  exposed 
  

   section. 
  Cardium 
  striatulum, 
  Discina 
  latissima, 
  and 
  Lucina 
  minuscula 
  

   occur 
  throughout 
  ; 
  Exogyra 
  virgula 
  occurs 
  near 
  the 
  base 
  of 
  the 
  

   upper 
  shales 
  ; 
  Ammonites 
  biplex, 
  Astarte 
  lineata, 
  Pecten 
  lens, 
  Avicula 
  

   vellicata, 
  Belemnites 
  Sowichii, 
  and 
  Lingula 
  ovalis 
  occur 
  in 
  the 
  

   upper 
  240 
  or 
  250 
  feet. 
  Near 
  the 
  base 
  of 
  the 
  Upper 
  Kimmeridge 
  

  

  

  