﻿HO 
  PROCEEDINGS 
  OE 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  search, 
  been 
  divided 
  into 
  Upper 
  Calcareous 
  Grit, 
  Coralline 
  Oolite, 
  

   and 
  Lower 
  Calcareous 
  Grit, 
  as 
  developed 
  in 
  Yorkshire 
  ; 
  we 
  must 
  

   not 
  assume, 
  however, 
  that 
  rocks 
  of 
  " 
  similar 
  lithological 
  character 
  

   are 
  the 
  equivalents 
  of 
  each 
  other 
  in 
  different 
  localities." 
  

  

  The 
  influence 
  that 
  physical 
  conditions 
  have 
  upon 
  the 
  contained 
  

   fauna 
  has 
  been 
  much 
  overlooked 
  by 
  paleontologists. 
  The 
  resem- 
  

   blance, 
  if 
  not 
  identity, 
  of 
  many 
  Corallian 
  species 
  with 
  those 
  be- 
  

   longing 
  to 
  the 
  Great 
  or 
  the 
  Inferior 
  Oolite 
  proves 
  that 
  much 
  of 
  the 
  

   peculiarity 
  of 
  the 
  Corallian 
  fauna 
  is 
  due, 
  not 
  to 
  the 
  lapse 
  of 
  time, 
  but 
  

   to 
  the 
  conditions 
  of 
  deposition 
  or 
  the 
  persistence 
  of 
  certain 
  physical 
  

   features 
  favourable 
  to 
  the 
  continuity 
  of 
  that 
  life 
  which 
  commenced 
  

   in 
  an 
  earlier 
  stage. 
  " 
  Nevertheless 
  Palceontology 
  does 
  not 
  fail 
  us 
  

   as 
  a 
  guide, 
  and 
  there 
  are 
  still 
  a 
  sufficiency 
  of 
  forms, 
  above 
  the 
  in- 
  

   fluence 
  of 
  physical 
  conditions, 
  which 
  indicate 
  satisfactorily 
  by 
  their 
  

   association 
  the 
  relative 
  age 
  of 
  the 
  deposits"*. 
  The 
  authors 
  en- 
  

   deavour, 
  through 
  the 
  physical 
  conditions 
  under 
  which 
  each 
  deposit 
  

   was 
  formed, 
  to 
  estimate 
  the 
  contained 
  fauna 
  at 
  its 
  true 
  chrono- 
  

   logical 
  value, 
  not, 
  howover, 
  omitting 
  the 
  history 
  of 
  the 
  beds 
  con- 
  

   taining 
  them. 
  

  

  The 
  areas 
  studied 
  and 
  described 
  in 
  the 
  paper 
  are 
  of 
  unequal 
  

   magnitude, 
  as 
  would 
  be 
  expected 
  ; 
  and 
  Messrs. 
  Blake 
  and 
  Hudleston 
  

   state 
  that 
  in 
  the 
  description 
  of 
  these 
  five 
  areas 
  their 
  endeavour 
  was 
  

   to 
  study 
  the 
  development, 
  physical 
  conditions, 
  and 
  correlations 
  of 
  

   the 
  Corallian 
  beds, 
  and 
  not 
  their 
  pure 
  stratigraphy. 
  

  

  The 
  Weymouth 
  district 
  affords 
  three 
  distinct 
  opportunities 
  for 
  

   studying 
  the 
  Corallian 
  beds 
  — 
  the 
  neighbourhood 
  of 
  Weymouth, 
  on 
  

   the 
  east 
  at 
  Osmington, 
  and 
  on 
  the 
  west 
  near 
  Abbotsbury. 
  The 
  

   authors 
  employ 
  local 
  names 
  to 
  designate 
  their 
  horizons 
  ; 
  and 
  from 
  

   the 
  Calcareous 
  Grit 
  (" 
  Nothc 
  Grits 
  " 
  of 
  the 
  Weymouth 
  area) 
  they 
  

   enumerate 
  23 
  species 
  — 
  2 
  Cephalopoda, 
  3 
  Gasteropoda, 
  15 
  Lamelli- 
  

   branchs, 
  2 
  Annelids, 
  and 
  1 
  Crinoid 
  (a 
  few 
  species 
  here 
  ally 
  the 
  

   Oxfordian 
  with 
  the 
  Corallian 
  group); 
  other 
  (G) 
  species 
  occur 
  to 
  

   increase 
  the 
  fauna 
  to 
  about 
  .30. 
  

  

  The 
  succeeding 
  "jSTothe 
  Clays" 
  have 
  yielded 
  16 
  species, 
  12 
  of 
  

   which 
  are 
  bivalves, 
  still 
  having 
  an 
  Oxfordian 
  facies. 
  The 
  " 
  Ben- 
  

   cliff 
  Grits 
  " 
  east 
  of 
  Sandsfoot 
  Castle, 
  20 
  feet 
  thick, 
  contain 
  few 
  fossils, 
  

   Gervillia 
  aviculoides, 
  Eccocjyra 
  nana, 
  and 
  Trigonia 
  corallina 
  being 
  

   most 
  characteristic. 
  

  

  The 
  Marls 
  and 
  Oolites 
  of 
  Osmington 
  (" 
  Osmington 
  Oolite 
  ") 
  con- 
  

   tain 
  17 
  species 
  — 
  12 
  bivalves, 
  4 
  Gasteropoda, 
  and 
  the 
  well-known 
  

   Echinobrissus 
  scutatus. 
  

  

  The 
  Trigonia 
  beds 
  (Coral-Bag 
  beds) 
  of 
  Weymouth 
  and 
  Osmington 
  

   named 
  in 
  the 
  paper 
  number 
  70 
  species 
  — 
  2 
  species 
  of 
  Ammonites, 
  

   17 
  Gasteropoda, 
  43 
  Lamellibranchs, 
  5 
  Echinodermata, 
  and 
  3 
  Acti- 
  

   nozoa 
  : 
  8 
  other 
  species 
  are 
  added 
  from 
  another 
  locality 
  (thus 
  in- 
  

   creasing 
  the 
  fanna 
  to 
  78) 
  ; 
  5 
  of 
  these 
  are 
  bivalves, 
  2 
  Echini, 
  and 
  

   Ammonites 
  plicatilis. 
  

  

  The 
  Sandsfoot-Castle 
  beds 
  (the 
  " 
  Kimmeridge 
  Passage-beds 
  ") 
  

   show 
  that 
  their 
  fossil 
  contents 
  were 
  entombed 
  on 
  the 
  actual 
  spot 
  

   * 
  Vide 
  Introduction 
  to 
  Messrs. 
  Blake 
  and 
  Hudleston's 
  paper, 
  loc. 
  cit. 
  

  

  