﻿Yol. 
  53.] 
  THE 
  CRETACEOUS 
  STRATA 
  OF 
  COUNTY 
  ANTRIM. 
  599 
  

  

  Carrier 
  ospongia 
  fangifonnis, 
  represents 
  the 
  Micraster 
  cor-anguinum 
  

   and 
  part 
  of 
  the 
  Marswpites 
  or 
  Belemnitella 
  \Actinocamax\ 
  vera- 
  

   zones. 
  

  

  6. 
  The 
  Spongiarian 
  Bed 
  must 
  be 
  classed 
  with 
  the 
  zone 
  of 
  

   Belemitella 
  [Actinocamax~\ 
  vera. 
  The 
  mulatto-stones 
  mainly 
  belong 
  

   to 
  the 
  zone 
  of 
  B. 
  [-4.] 
  qiiadrata, 
  but 
  also 
  in 
  part 
  to 
  the 
  preceding 
  

   and 
  succeeding 
  zones. 
  

  

  7. 
  The 
  White 
  Limestone 
  is 
  a 
  member 
  of 
  the 
  zone 
  of 
  

   Belemnitella 
  mucronata, 
  there 
  being 
  little 
  evidence 
  in 
  favour 
  of 
  the 
  

   existence 
  of 
  still 
  higher 
  strata. 
  

  

  The 
  first 
  four 
  of 
  the 
  above 
  divisions 
  were 
  classed 
  by 
  Tate 
  as 
  the 
  

   Hibernian 
  Greensands, 
  under 
  the 
  impression 
  that 
  all 
  these 
  beds 
  

   were 
  Cenomanian. 
  We 
  have 
  seen, 
  however, 
  as 
  Barrois 
  had 
  already 
  

   pointed 
  out, 
  that 
  the 
  Inoceramus-zone 
  cannot 
  be 
  thus 
  regarded. 
  

   The 
  first 
  three 
  might 
  very 
  conveniently 
  be 
  retained 
  under 
  the 
  old 
  

   name 
  ; 
  but 
  if 
  a 
  short 
  designation 
  be 
  needed 
  for 
  the 
  Chloritic 
  Sands 
  

   of 
  the 
  Eastern 
  Division, 
  the 
  term 
  ' 
  Antrim 
  Beds 
  ' 
  suggests 
  itself 
  to 
  

   me, 
  which 
  would 
  include 
  all 
  the 
  strata 
  characterized 
  by 
  Spondylus 
  

   spinosus 
  and 
  Inoceramus-f 
  ragments, 
  having 
  the 
  Spongiarian 
  band 
  

   at 
  the 
  summit. 
  The 
  type-section 
  for 
  these 
  beds 
  is 
  the 
  quarry 
  of 
  

   Barney's 
  Point, 
  in 
  Islandmagee. 
  

  

  IV. 
  General 
  Considerations. 
  

  

  Having 
  dealt 
  with 
  the 
  various 
  lithological 
  and 
  zonal 
  divisions 
  in 
  

   detail, 
  it 
  will 
  now 
  be 
  advisable 
  to 
  consider 
  the 
  general 
  questions 
  

   which 
  arise 
  out 
  of 
  our 
  previous 
  study. 
  

  

  1. 
  We 
  have 
  observed 
  that 
  there 
  are 
  certain 
  organic 
  remains 
  in 
  

   the 
  Glauconitic 
  Sands 
  and 
  Yellow 
  Sandstones 
  of 
  the 
  Eastern 
  

   Division, 
  which 
  suggest 
  higher 
  zonal 
  conditions 
  than 
  those 
  indicated 
  

   by 
  the 
  species 
  with 
  which 
  they 
  are 
  associated, 
  and 
  it 
  is 
  mainly 
  

   these 
  which 
  have 
  guided 
  Barrois 
  in 
  his 
  classification 
  of 
  the 
  lower 
  

   Irish 
  beds. 
  They 
  play, 
  it 
  is 
  true, 
  a 
  purely 
  subordinate 
  part 
  in 
  the 
  

   fauna, 
  but 
  their 
  presence 
  demands 
  consideration, 
  and 
  various 
  possi- 
  

   bilities 
  may 
  be 
  suggested. 
  

  

  (a) 
  The 
  Eastern 
  Division 
  I 
  regard 
  as 
  having 
  been 
  in 
  deeper 
  water 
  

   than 
  the 
  Central, 
  firstly, 
  because 
  the 
  detrital 
  deposits 
  are 
  generally 
  

   thinner 
  here 
  than 
  in 
  the 
  Central 
  Division 
  ; 
  secondly, 
  because 
  

   brachiopoda, 
  corals, 
  sea-urchins, 
  and 
  chlamyd 
  bivalves 
  are 
  present 
  

   in 
  its 
  lower 
  strata 
  ; 
  thirdly, 
  because 
  large 
  dimyarian 
  bivalves, 
  such 
  

   as 
  the 
  Trigonice, 
  Area, 
  Thetis, 
  etc., 
  so 
  abundant 
  in 
  the 
  Central, 
  are 
  

   very 
  rare 
  in 
  the 
  Eastern 
  fauna. 
  Again, 
  there 
  seems 
  to 
  be 
  a 
  growing 
  

   belief 
  that 
  the 
  organic 
  changes 
  in 
  the 
  English 
  Upper 
  Greensand 
  

   are 
  such 
  as 
  would 
  result 
  from 
  gradual 
  depression. 
  It 
  may 
  be 
  then 
  

   that 
  this 
  is 
  a 
  case 
  where 
  a 
  deeper 
  is 
  co-existent 
  with 
  a 
  shallower- 
  

   water 
  fauna, 
  and 
  not 
  successional, 
  as 
  in 
  England. 
  

  

  (b) 
  Another 
  possible 
  view 
  is 
  that 
  an 
  older 
  fauna 
  continued 
  living 
  

   longer 
  near 
  the 
  Irish 
  shore 
  than 
  in 
  England, 
  where 
  a 
  deeper-water 
  

   one 
  had 
  already 
  established 
  itself, 
  and 
  had 
  partly 
  invaded 
  the 
  Irish 
  

   area. 
  This 
  seems 
  to 
  me 
  less 
  tenable 
  than 
  the 
  first 
  view, 
  because 
  all 
  

  

  