﻿V°l- 
  53-] 
  THE 
  CRETACEOUS 
  STRATA 
  OF 
  COUNTY 
  ANTRIM. 
  595 
  

  

  I 
  have 
  been 
  much 
  struck 
  with 
  the 
  resemblance 
  which 
  some 
  of 
  

   the 
  Irish 
  fossils 
  have 
  to 
  the 
  English 
  species 
  from 
  that 
  horizon. 
  

   For 
  example, 
  the 
  Irish 
  specimens 
  of 
  Micraster 
  breviporus 
  agree 
  

   almost 
  absolutely 
  in 
  size 
  with 
  those 
  obtained 
  from 
  the 
  base 
  of 
  the 
  

   Micraster 
  cor-iestudinarium-zone 
  in 
  Surrey 
  and 
  at 
  Eastbourne, 
  

   or 
  from 
  the 
  Chalk 
  Rock 
  at 
  Baldock, 
  near 
  Hitchin, 
  while 
  the 
  

   Rhynchonella 
  plicatilis 
  and 
  Rh. 
  limbata 
  are 
  very 
  similar 
  in 
  both 
  

   cases. 
  Also, 
  as 
  Barrois 
  has 
  urged, 
  Spondylus 
  spinosus, 
  Ostrea 
  

   semiplana, 
  and 
  Inoceramus 
  sp. 
  are 
  particularly 
  abundant 
  in 
  the 
  

   upper 
  part 
  of 
  the 
  Turonian. 
  The 
  fauna, 
  taken 
  as 
  a 
  whole, 
  may 
  be 
  

   termed 
  that 
  of 
  the 
  reversing 
  layer, 
  or 
  the 
  point 
  where 
  the 
  secondary 
  

   elevation 
  leading 
  to 
  the 
  formation 
  of 
  the 
  Chalk 
  Rock 
  attained 
  its 
  

   maximum 
  ; 
  and 
  indeed, 
  if 
  anything, 
  these 
  sandy 
  limestones 
  have 
  

   been 
  formed 
  on 
  the 
  depression 
  side 
  of 
  it. 
  

  

  Xor 
  have 
  I 
  been 
  able 
  to 
  confirm 
  Barrois's 
  discovery 
  of 
  Galerites 
  

   subrotundus 
  and 
  Rhynclionella 
  Cuvieri. 
  These 
  must 
  be 
  uncommon, 
  

   and 
  would 
  consequently 
  not 
  affect 
  the 
  general 
  Chalk 
  Rock 
  

   character 
  of 
  the 
  organisms 
  present. 
  

  

  Looking 
  at 
  the 
  question 
  from 
  a 
  historical 
  point 
  of 
  view, 
  it 
  would 
  

   appear 
  that 
  the 
  Eastern 
  Division 
  of 
  Ireland 
  had 
  now 
  joined 
  in 
  the 
  

   great 
  second 
  movement 
  of 
  depression 
  which 
  appears 
  to 
  have 
  begun 
  

   in 
  England 
  after 
  the 
  formation 
  of 
  the 
  Chalk 
  Rock, 
  the 
  shallower 
  

   waters 
  of 
  the 
  Antrim 
  Sea 
  preserving 
  the 
  fauna 
  of 
  the 
  transition- 
  

   period 
  longer 
  than 
  was 
  the 
  case 
  in 
  England. 
  If 
  this 
  view 
  be 
  

   adopted, 
  these 
  beds 
  will 
  have 
  to 
  be 
  considered 
  as 
  Lowest 
  Senonian, 
  

   but 
  still 
  presenting 
  a 
  strong 
  Turonian 
  aspect. 
  

  

  Chloritic 
  Chalk. 
  (Zone 
  o£ 
  Echinocorys 
  gibbus.~) 
  

  

  The 
  principal 
  fossils 
  are 
  : 
  — 
  

  

  Mollusca 
  : 
  Spondylus 
  spinosus, 
  Sow. 
  

  

  Echtnodermata 
  : 
  Echinocorys 
  gibbus, 
  Lam., 
  Cidaris 
  sceptrifera, 
  

   Mant. 
  (probably). 
  

  

  Vermes 
  : 
  Serpula 
  filiformis, 
  Sow. 
  

  

  Crinoidea 
  : 
  Bourgueticrinus 
  sp. 
  

  

  Brachiopoda 
  : 
  Terebratula 
  carnea, 
  Sow. 
  

  

  Actinozoa 
  : 
  Parasmilia 
  centralis, 
  Mant. 
  

  

  Porifera: 
  Gamer 
  ospongia 
  fungiformis, 
  Goldf., 
  Ventriculites 
  sp. 
  

  

  This 
  zone 
  differs 
  from 
  the 
  last, 
  with 
  which 
  it 
  is 
  intimately 
  con- 
  

   nected, 
  only 
  in 
  the 
  increase 
  of 
  the 
  calcareous 
  constituents 
  and 
  the 
  

   thoroughly 
  deep-sea 
  character 
  of 
  the 
  fauna, 
  the 
  large 
  mollusca 
  

   having 
  almost 
  entirely 
  disappeared. 
  It 
  apparently 
  represents, 
  with 
  

   the 
  sands 
  previously 
  described, 
  the 
  whole 
  of 
  the 
  Lower 
  Senonian, 
  

   minus 
  the 
  Belemnitella 
  [Actinocamaoc] 
  vera-zone. 
  The 
  main 
  feature 
  

   is 
  the 
  abundance 
  of 
  Echinocorys 
  scutatus, 
  Terebratula 
  camea, 
  and 
  

   Camer 
  ospongia 
  fungiformis, 
  all 
  of 
  which 
  fossils 
  connect 
  it 
  with 
  

   the 
  zone 
  above, 
  but 
  as 
  B. 
  \Actinocamax\ 
  vera 
  has 
  not 
  yet 
  been 
  

   obtained 
  in 
  these 
  beds, 
  they 
  must 
  at 
  present 
  be 
  excluded 
  from 
  that 
  

   zone. 
  

  

  2b2 
  

  

  