﻿570 
  DE. 
  W. 
  FKASEK 
  HUME 
  ON 
  [DeC. 
  1897, 
  

  

  2. 
  Haplophragmioid 
  or 
  Cristellarian 
  types, 
  in 
  which 
  the 
  casts 
  

   commence 
  as 
  spirally-convoluted 
  chambers, 
  the 
  later 
  chambers 
  

   becoming 
  rectilinear, 
  or 
  in 
  some 
  cases 
  slightly 
  curved 
  inward, 
  giving 
  

   rise 
  to 
  crosier 
  -like 
  forms. 
  

  

  3. 
  Globigerinoid 
  types, 
  the 
  chambers 
  being 
  very 
  globular 
  in 
  form, 
  

   and 
  in 
  general 
  not 
  presenting 
  the 
  symmetrical 
  arrangement 
  dis- 
  

   played 
  in 
  the 
  previous 
  varieties. 
  

  

  4. 
  Tritaxian 
  types, 
  which 
  are 
  much 
  more 
  indefinite 
  and 
  tri- 
  

   angular 
  in 
  section, 
  one 
  of 
  the 
  edges 
  being 
  generally 
  replaced 
  by 
  a 
  

   narrow 
  flat 
  plane. 
  

  

  5. 
  Together 
  with 
  the 
  above, 
  there 
  are 
  a 
  number 
  of 
  oval 
  forms 
  

   having 
  a 
  depression 
  running 
  parallel 
  to 
  the 
  major 
  axis, 
  which 
  can 
  

   be 
  explained 
  only 
  as 
  being 
  the 
  internal 
  casts 
  of 
  ostracod 
  valves, 
  

   though 
  any 
  attempt 
  at 
  closer 
  identification 
  is 
  impossible. 
  

  

  6. 
  One 
  beautiful 
  cast 
  of 
  an 
  undoubted 
  Cristellaria 
  was 
  observed, 
  

   every 
  chamber 
  being 
  clearly 
  outlined, 
  the 
  general 
  form 
  being 
  that 
  

   of 
  Cr. 
  gibba. 
  It 
  will 
  be 
  noticed 
  that 
  Textularian 
  and 
  Milioline 
  types 
  

   are 
  unrepresented, 
  nor 
  have 
  any 
  sponge-casts 
  been 
  observed. 
  

  

  The 
  glauconitic 
  material 
  from 
  this 
  locality 
  has 
  been 
  chemically 
  

   examined 
  by 
  Mr. 
  A. 
  P. 
  Hoskins, 
  1 
  and 
  the 
  general 
  results 
  are 
  of 
  some 
  

   interest. 
  The 
  point 
  on 
  which 
  he 
  lays 
  most 
  stress 
  is 
  the 
  relative 
  

   poverty 
  in 
  silica 
  of 
  the 
  Woodburn 
  specimens, 
  the 
  ascertained 
  amount 
  

   (40% 
  Si0 
  2 
  ) 
  being 
  10°/ 
  less 
  than 
  the 
  lowest 
  percentage 
  obtained 
  by 
  

   Sipocz 
  in 
  analyses 
  of 
  Challenger 
  samples. 
  The 
  ferric 
  oxide 
  is 
  

   also 
  4°/ 
  less 
  than 
  the 
  mean, 
  while 
  the 
  percentage 
  of 
  potash 
  is 
  nearly 
  

   double 
  that 
  found 
  in 
  the 
  modern 
  glauconite. 
  

  

  C. 
  The 
  lighter 
  residue 
  mainly 
  consists 
  of 
  small 
  quartz-grains 
  

   •25 
  mm. 
  in 
  diameter. 
  

  

  D. 
  The 
  heavy-residue 
  minerals, 
  separated 
  by 
  means 
  of 
  cadmium 
  

   borotungstate 
  (sp. 
  gr. 
  2'9), 
  are 
  as 
  follows 
  : 
  — 
  

  

  Rutile. 
  This 
  mineral 
  occurs 
  both 
  as 
  crystals 
  and 
  grains. 
  The 
  

   crystals 
  have 
  a 
  maximum 
  length 
  of 
  *18 
  mm., 
  breadth 
  -07 
  mm., 
  the 
  

   faces 
  of 
  the 
  prism 
  and 
  pyramid 
  being 
  well 
  developed. 
  Their 
  

   pleochroism 
  is 
  deep 
  yellow 
  to 
  straw-yellow, 
  and 
  they 
  possess 
  a 
  

   prominent 
  black 
  border, 
  due 
  to 
  their 
  high 
  refractive 
  index. 
  The 
  

   enclosures 
  are 
  numerous, 
  and 
  have 
  in 
  most 
  cases 
  irregular 
  outlines. 
  

   In 
  one 
  crystal 
  the 
  central 
  portion 
  polarized 
  in 
  a 
  deep 
  orange-red, 
  

   the 
  outer 
  part 
  being 
  bright 
  golden 
  yellow. 
  Orange-yellow 
  grains 
  of 
  

   rutile 
  are 
  numerous, 
  as 
  also 
  very 
  rounded 
  examples 
  of 
  zircon. 
  

   These 
  are 
  easily 
  noticed 
  on 
  account 
  of 
  their 
  high 
  refractive 
  index 
  

   and 
  high 
  order 
  polarization-colours. 
  A 
  few 
  well-marked 
  crystals 
  are 
  

   present, 
  the 
  largest 
  having 
  a 
  length 
  of 
  '17 
  mm., 
  with 
  the 
  prismatic 
  

   faces 
  well 
  developed 
  and 
  the 
  pyramidal 
  faces 
  much 
  reduced. 
  

  

  Muscovite 
  is 
  not 
  uncommon, 
  in 
  thin 
  silvery 
  flakes, 
  which, 
  owing 
  

   to 
  their 
  extreme 
  tenuity, 
  do 
  not 
  display 
  the 
  high 
  colours 
  familiar 
  

   in 
  the 
  same 
  mineral 
  when 
  examined 
  under 
  crossed 
  nicols 
  in 
  rock- 
  

   sections. 
  In 
  nearly 
  all 
  cases 
  they 
  are 
  seen 
  to 
  be 
  of 
  hexagonal 
  

   outline, 
  being 
  viewed 
  at 
  right 
  angles 
  to 
  the 
  basal 
  plane. 
  

  

  Biotiteis 
  also 
  present 
  in 
  brown 
  scales, 
  which 
  practically 
  display 
  

   1 
  Proc. 
  Belfast 
  Nat. 
  Field 
  Club, 
  1894-95, 
  pp. 
  1-2. 
  

  

  