﻿Vol. 
  53.] 
  THE 
  CRETACEOUS 
  STEATA 
  OF 
  COTTXTY 
  AXTBIJI. 
  583 
  

  

  finer 
  residue 
  is 
  interesting 
  from 
  the 
  abundance 
  of 
  glauconitic 
  casts 
  

   of 
  sponge-spicules. 
  Seme 
  of 
  these 
  are 
  merely 
  tapering 
  rods, 
  others 
  

   are 
  expanded 
  at 
  one 
  extremity, 
  forming 
  a 
  flat 
  or 
  subdivided 
  head, 
  

   separated 
  from 
  the 
  main 
  body 
  by 
  a 
  constriction, 
  and 
  some 
  are 
  

   also 
  spindle-shaped. 
  Most 
  of 
  these 
  are 
  of 
  a 
  deep-green 
  colour, 
  

   therein 
  contrasting 
  with 
  the 
  yellow 
  casts 
  of 
  the 
  foraminifera. 
  

   Of 
  these, 
  rounded 
  individual 
  chambers 
  are 
  most 
  numerous, 
  but 
  unions 
  

   of 
  such 
  are 
  not 
  uncommon, 
  though 
  the 
  latter 
  are 
  not 
  so 
  well 
  pre- 
  

   served 
  as 
  in 
  the 
  previous 
  examples. 
  Portions 
  of 
  a 
  Textularian 
  cast, 
  

   showing 
  the 
  alternating 
  character 
  of 
  the 
  chambers, 
  and 
  Glohigerince 
  

   have 
  been 
  observed. 
  Fragments 
  of 
  delicate 
  silicified 
  tests 
  are 
  also 
  

   present. 
  

  

  No 
  heavy 
  minerals 
  were 
  obtained 
  by 
  the 
  use 
  of 
  heavy 
  liquids. 
  

  

  The 
  most 
  noticeable 
  features 
  in 
  this 
  limestone 
  are 
  : 
  — 
  

  

  1. 
  Quartz 
  -fragments 
  less 
  than 
  1 
  mm. 
  in 
  diameter. 
  

  

  2. 
  The 
  increasing 
  abundance 
  of 
  sponge-spicule 
  casts. 
  

  

  3. 
  The 
  absence 
  of 
  heavy 
  minerals. 
  

  

  Chalk, 
  12 
  feet 
  above 
  the 
  Conglomerate. 
  

   (No. 
  9 
  in 
  Table 
  II.) 
  

  

  After 
  solution 
  in 
  acid, 
  80-92 
  grammes 
  of 
  chalk 
  yielded 
  1*675 
  

   gramme 
  of 
  residue=2'07 
  %• 
  T 
  ne 
  analysis 
  therefore 
  gives 
  

  

  Carbonate 
  of 
  lime 
  97'93 
  % 
  

  

  Clay, 
  etc 
  = 
  1-522 
  gr. 
  = 
  1-88 
  % 
  

  

  Heavy 
  residue 
  = 
  -153 
  „ 
  = 
  -189°/o 
  

  

  100 
  

  

  The 
  residue 
  above 
  *5 
  mm. 
  in 
  diameter 
  consisted 
  almost 
  entirely 
  

   of 
  the 
  siliceous 
  meshes 
  formed 
  in 
  the 
  interspaces 
  between 
  the 
  prisms 
  

   of 
  Inoceramus 
  -shells. 
  Viewed 
  from 
  the 
  side, 
  the 
  delicate 
  columns 
  

   are 
  beautifully 
  shown 
  in 
  the 
  larger 
  specimens, 
  while 
  in 
  most 
  

   the 
  replacing 
  silica 
  forms 
  thin 
  chalcedonic 
  films, 
  dividing 
  up 
  the 
  

   test 
  into 
  irregular 
  networks. 
  The 
  chalcedony 
  appears 
  snow-white 
  

   on 
  the 
  upper 
  and 
  outer 
  surfaces. 
  An 
  Ammodiscus 
  incertus 
  and 
  

   other 
  organic 
  bodies 
  are 
  present, 
  replaced 
  in 
  snow-white 
  chalcedony. 
  

   A 
  few 
  rounded 
  and 
  subangular 
  grains 
  of 
  quartz 
  were 
  also 
  observed, 
  

   and 
  some 
  solid 
  white 
  masses 
  of 
  doubtful 
  origin, 
  breaking 
  with 
  an 
  

   even 
  fracture. 
  

  

  The 
  finer 
  residue 
  consists 
  mainly 
  of 
  films 
  derived 
  from 
  Inocerami 
  

   as 
  described 
  above, 
  numerous 
  rounded 
  yellow 
  spheres, 
  the 
  casts 
  of 
  

   individual 
  foraminiferal 
  chambers, 
  in 
  some 
  cases 
  united 
  and 
  then 
  

   displaying 
  the 
  original 
  form 
  of 
  the 
  organisms. 
  Globigerina 
  is 
  the 
  

   most 
  common 
  genus, 
  Textularian 
  types 
  not 
  having 
  been 
  observed. 
  

   In 
  addition, 
  rods, 
  the 
  internal 
  casts 
  of 
  sponge-spicules, 
  are 
  numerous, 
  

   but 
  much 
  smaller 
  than 
  those 
  observed 
  in 
  previous 
  cases. 
  Deep- 
  

   green 
  glauconitic 
  grains, 
  though 
  noticed, 
  were 
  rare. 
  The 
  detrital 
  

   material 
  is 
  composed 
  of 
  small 
  colourless 
  angular 
  grains 
  of 
  quartz, 
  

  

  