﻿Yol. 
  53.] 
  THE 
  CRETACEOUS 
  STRATA 
  OF 
  COUNTY 
  ANTRIM. 
  577 
  

  

  Chloritic 
  Chalk 
  (Spongiarian 
  Zone). 
  

   Woodburn 
  Glen. 
  (No. 
  2 
  in 
  Table 
  II.) 
  

  

  After 
  solution 
  80-66 
  grammes 
  yielded 
  4*88 
  grammes 
  of 
  insoluble 
  

   material, 
  3-96 
  of 
  which 
  may 
  be 
  classed 
  as 
  heavy 
  residue. 
  

   Total 
  composition 
  : 
  — 
  

  

  Carbonate 
  of 
  lime 
  93-95% 
  

  

  Clay,etc 
  = 
  "92 
  gr. 
  = 
  M4% 
  

  

  Heavy 
  residue 
  = 
  3-96 
  grs. 
  = 
  491% 
  

  

  100 
  

  

  The 
  residue 
  exceeding 
  -5 
  mm. 
  in 
  diameter 
  consisted 
  of 
  angular 
  

   colourless 
  flakes 
  of 
  quartz, 
  and 
  a 
  great 
  abundance 
  of 
  glauconitic 
  

   grains, 
  most 
  of 
  which 
  are 
  changing 
  to 
  a 
  yellowish 
  or 
  reddish 
  

   alteration-product, 
  having 
  a 
  limonitic 
  aspect. 
  A 
  special 
  feature 
  is 
  

   the 
  perfect 
  preservation 
  of 
  many 
  of 
  the 
  casts, 
  the 
  nature 
  of 
  the 
  

   foraminifera 
  being 
  easily 
  determinable, 
  while 
  spicular 
  meshes 
  are 
  

   also 
  conspicuous. 
  A 
  few 
  delicate 
  white 
  siliceous 
  tests 
  of 
  forami- 
  

   nifera 
  are 
  also 
  present. 
  

  

  Mr. 
  Chapman 
  has 
  been 
  able 
  to 
  identify 
  the 
  following 
  species 
  

   from 
  these 
  well-preserved 
  glauconitic 
  casts, 
  and 
  the 
  remarks 
  attached 
  

   are 
  his 
  : 
  — 
  

  

  Textularia 
  globulosa, 
  Ehr 
  Internal 
  casts, 
  frequent. 
  

  

  T. 
  anceps, 
  Reuss 
  One 
  example 
  of 
  an 
  internal 
  cast. 
  

  

  Verneuilina 
  triquetra 
  (Miinst.) 
  ... 
  An 
  external 
  cast. 
  

  

  Tritaxia 
  tricarinata, 
  Reuss 
  Internal 
  casts. 
  

  

  Bulimina 
  Orbignyi, 
  Reuss 
  An 
  external 
  cast. 
  

  

  B. 
  elegans, 
  d'Orb 
  „ 
  „ 
  „ 
  

  

  B. 
  Murchisoniana, 
  d'Orb 
  „ 
  „ 
  „ 
  

  

  B. 
  obtusa, 
  d'Orb 
  ,, 
  „ 
  ,, 
  

  

  B. 
  variabilis, 
  d'Orb 
  „ 
  ,, 
  „ 
  

  

  Globigerina 
  hullo 
  ides, 
  d'Orb 
  „ 
  „ 
  „ 
  

  

  Gl. 
  (Bquilateralis, 
  Brady 
  „ 
  „ 
  ,, 
  

  

  ? 
  Discorbina 
  rosacea 
  (d'Orb.) 
  An 
  internal 
  cast. 
  

  

  Anomalina 
  ammonoid.es 
  (Reuss) 
  ... 
  External 
  casts. 
  

  

  ? 
  A. 
  grosserugosa 
  (Giimbel) 
  External 
  and 
  internal 
  casts. 
  

  

  Truncatulina 
  Ungeriana 
  (d'Orb.) 
  . 
  . 
  Internal 
  casts. 
  

  

  For 
  further 
  notes 
  on 
  these 
  casts, 
  see 
  p. 
  581. 
  

  

  In 
  the 
  finer 
  residue, 
  angular 
  transparent 
  quartz, 
  glauconitic 
  

   spicular 
  meshes, 
  fragments 
  of 
  silicified 
  foraminifera, 
  and 
  hexagonal 
  

   flakes 
  of 
  muscovite 
  are 
  numerous. 
  The 
  glauconite-grains 
  and 
  

   quartz 
  are 
  often 
  coated 
  with 
  a 
  layer 
  of 
  red-brown 
  limonite. 
  

   In 
  general 
  the 
  former 
  do 
  not 
  show 
  much 
  trace 
  of 
  their 
  organic 
  origin, 
  

   except 
  in 
  the 
  case 
  of 
  the 
  green 
  rods 
  (casts 
  of 
  spicular 
  axial 
  canals 
  

   presumably), 
  which 
  are 
  relatively 
  most 
  abundant 
  in 
  the 
  finest 
  

   portion 
  of 
  the 
  residue. 
  

  

  Heavy 
  minerals 
  are 
  less 
  marked 
  than 
  in 
  previous 
  cases, 
  though 
  

   zircon, 
  in 
  colourless 
  grains 
  ; 
  rutile, 
  in 
  large 
  yellow 
  grains 
  (no 
  deep 
  

   red 
  varieties 
  being 
  noted) 
  ; 
  tourmaline, 
  fairly 
  abundant 
  and 
  in 
  good 
  

   crystals 
  ; 
  garnet, 
  in 
  small 
  pink 
  rhombic 
  dodecahedra 
  and 
  larger 
  

   flat 
  fragments 
  ; 
  felspar, 
  undergoing 
  kaolinization 
  ; 
  and 
  chlorite, 
  

   in 
  bine-green 
  flakes, 
  have 
  been 
  noticed. 
  

  

  Q.J.G.S. 
  No. 
  212. 
  2q 
  

  

  