﻿Vol. 
  53.J 
  THE 
  CRETACEOUS 
  STRATA 
  OF 
  COUNTY 
  ANTRIM. 
  601 
  

  

  occurrence 
  of 
  the 
  same 
  nature. 
  The 
  three 
  movements 
  appear 
  

   to 
  have 
  left 
  very 
  marked 
  effects 
  in 
  Ireland, 
  these 
  being 
  inten- 
  

   sified 
  owing 
  to 
  the 
  immediate 
  proximity 
  of 
  land. 
  The 
  changes 
  

   during 
  Upper 
  Greensand 
  and 
  Cenomanian 
  times 
  run 
  parallel 
  with 
  

   those 
  taking 
  place 
  in 
  Western 
  England; 
  but 
  an 
  elevation 
  which, 
  from 
  

   the 
  Irish 
  evidence, 
  must 
  have 
  taken 
  place 
  later 
  than 
  the 
  beginning 
  

   of 
  the 
  Cenomanian 
  seems 
  to 
  have 
  been 
  the 
  cause 
  of 
  the 
  uncon- 
  

   formities 
  which 
  have 
  been 
  noted, 
  especially 
  in 
  the 
  Central 
  Division. 
  

   The 
  advance 
  of 
  the 
  second 
  submergence 
  is 
  marked 
  by 
  both 
  overlap 
  

   and 
  unconformity, 
  the 
  character 
  of 
  the 
  incoming 
  fauna 
  being, 
  as 
  

   already 
  observed, 
  of 
  highest 
  Turonian 
  or 
  lowest 
  Senonian 
  age, 
  and 
  

   thus 
  indicating 
  that 
  the 
  oscillations 
  were 
  closely 
  parallel, 
  or 
  con- 
  

   nected, 
  with 
  those 
  occurring 
  in 
  the 
  English 
  areas. 
  The 
  first 
  signs 
  

   of 
  the 
  new 
  conditions 
  are 
  observed 
  in 
  the 
  east 
  of 
  the 
  Eastern 
  

   Division, 
  where 
  there 
  is 
  merely 
  a 
  slight 
  trace 
  of 
  lithological 
  uncon- 
  

   formity, 
  but 
  a 
  considerable 
  faunal 
  break. 
  The 
  lower 
  beds 
  of 
  the 
  

   Inoceramus-zone 
  are 
  limited 
  to 
  the 
  centre 
  of 
  this 
  division, 
  but 
  the 
  

   higher 
  ones 
  overlap 
  the 
  older 
  strata 
  both 
  to 
  the 
  south 
  and 
  north, 
  

   invading 
  the 
  Central 
  area 
  on 
  the 
  one 
  hand, 
  and 
  extending 
  to 
  Carn- 
  

   lough 
  on 
  the 
  other. 
  Approaching 
  the 
  Southern 
  and 
  Peninsular 
  

   regions, 
  the 
  unconformity 
  occurs 
  at 
  the 
  base 
  of 
  higher 
  and 
  higher 
  

   zones, 
  until 
  in 
  isolated 
  exposures 
  in 
  these 
  districts 
  the 
  Belemnitella 
  

   mucronata-zone 
  itself 
  rests 
  with 
  an 
  unconformable 
  junction 
  upon 
  

   strata 
  of 
  Triassic, 
  Carboniferous, 
  or 
  even 
  earlier 
  age, 
  so 
  that 
  at 
  the 
  

   close 
  of 
  the 
  Upper 
  Chalk 
  period 
  every 
  part 
  of 
  the 
  Antrim 
  area 
  must 
  

   have 
  been 
  submerged. 
  

  

  4. 
  One 
  of 
  the 
  most 
  interesting 
  occurrences 
  in 
  this 
  connexion 
  is 
  

   the 
  presence 
  of 
  definite 
  beaches 
  of 
  Upper 
  Chalk 
  age, 
  characterized 
  

   by 
  the 
  large 
  size 
  of 
  the 
  mica-schist 
  and 
  other 
  fragments 
  which 
  

   compose 
  them, 
  and 
  at 
  the 
  same 
  time 
  containing 
  a 
  rich 
  and 
  dis- 
  

   tinctive 
  fauna. 
  These 
  beaches, 
  which 
  have 
  evidently 
  been 
  formed 
  

   during 
  the 
  period 
  of 
  maximum 
  depression, 
  are 
  inhabited 
  by 
  two 
  sets 
  

   of 
  organisms, 
  some, 
  such 
  as 
  the 
  gasteropoda 
  and 
  dimyarian 
  bivalves, 
  

   being 
  shallow-water 
  inhabitants, 
  others 
  of 
  deep-sea 
  origin, 
  but 
  

   stunted 
  in 
  growth 
  because 
  they 
  lived 
  under 
  abnormal 
  conditions 
  of 
  

   depth, 
  etc., 
  the 
  types 
  being 
  the 
  small 
  Galerites 
  which 
  are 
  among 
  the 
  

   commonest 
  genera 
  present. 
  It 
  is 
  possible, 
  indeed, 
  to 
  trace 
  every 
  

   gradation 
  from 
  these 
  undoubted 
  beaches 
  to 
  the 
  pebble-conglomeratic 
  

   limestones 
  and 
  mulatto-stones 
  of 
  the 
  same 
  period, 
  these 
  again 
  passing, 
  

   by 
  gradual 
  diminution 
  of 
  the 
  detrital 
  constituents, 
  into 
  the 
  glauconitic 
  

   and 
  sponge-containing 
  limestones 
  of 
  the 
  deep-water 
  divisions. 
  

  

  5. 
  The 
  geological 
  evidence 
  in 
  favour 
  of 
  the 
  existence 
  of 
  marine 
  

   currents 
  must 
  be, 
  as 
  a 
  general 
  rule, 
  only 
  indirect, 
  but 
  at 
  times 
  a 
  

   combination 
  of 
  circumstances 
  unites 
  to 
  witness 
  to 
  their 
  action. 
  

   Eor 
  instance, 
  in 
  the 
  Exogyra 
  columba-zone 
  especially, 
  a 
  number 
  

   of 
  facts 
  testify 
  to 
  the 
  existence 
  of 
  a 
  current 
  of 
  some 
  magnitude 
  ; 
  

   thus, 
  a 
  new 
  fauna, 
  not 
  previously 
  represented 
  in 
  Ireland, 
  replaces 
  

   the 
  other 
  species, 
  individual 
  forms 
  by 
  their 
  abundance 
  characterizing 
  

   bands 
  of 
  no 
  great 
  thickness 
  and 
  limited 
  horizontal 
  extension 
  (as, 
  

  

  