﻿556 
  DK. 
  W. 
  PKASEK 
  HUME 
  OHf 
  [Dec. 
  1 
  897, 
  

  

  Sponclylus 
  sjpinosus, 
  Sow., 
  Pecten 
  \Janira] 
  quinquecostatus, 
  Sow., 
  

   and 
  Terebratula 
  carnea, 
  Sow. 
  A 
  Cidaris-s^iue 
  and 
  Ostrea 
  semiplana 
  

   have 
  also 
  been 
  obtained, 
  the 
  Cidaris 
  noted 
  here 
  having 
  always 
  

   been 
  classed 
  with 
  0. 
  subvesiculosa, 
  d'Orb. 
  Of 
  the 
  greatest 
  interest, 
  

   perhaps, 
  is 
  the 
  occurrence 
  of 
  Echinocorys 
  scutatus 
  var. 
  gibbus, 
  Lam., 
  

   at 
  this 
  horizon, 
  two 
  characteristic 
  specimens 
  being 
  obtained 
  

   by 
  me 
  in 
  the 
  northern 
  glen, 
  and 
  these 
  were 
  in 
  close 
  connexion 
  

   with 
  the 
  fragmentary 
  Inocerami, 
  Sjpondylus, 
  and 
  Janira. 
  Special 
  

   stress 
  must 
  be 
  laid 
  upon 
  the 
  occurrence 
  of 
  this 
  sea-urchin 
  at 
  

   this 
  locality, 
  because 
  Tate 
  has 
  placed 
  the 
  Inoceramus-bnud 
  in 
  the 
  

   Lower 
  Chalk, 
  or 
  Cenomanian, 
  and 
  Barrois 
  does 
  not 
  appear 
  to 
  have 
  

   obtained 
  it 
  here. 
  In 
  addition 
  Rliynclionella 
  robusta, 
  Tate, 
  a 
  well- 
  

   marked 
  variety 
  of 
  Rh. 
  limbata, 
  Dav., 
  occurs 
  at 
  this 
  horizon. 
  

  

  If 
  some 
  of 
  the 
  Inoceramus-shells 
  be 
  placed 
  in 
  dilute 
  hydrochloric 
  

   acid, 
  the 
  greater 
  portion 
  of 
  the 
  shell 
  dissolves 
  away, 
  leaving 
  an 
  

   open 
  hexagonal 
  mesh 
  of 
  siliceous 
  material 
  behind. 
  Mr. 
  Chapman 
  

   has 
  obtained 
  similar 
  results 
  in 
  the 
  Bargate 
  Beds, 
  and 
  has 
  also 
  

   shown 
  me 
  a 
  section 
  in 
  which 
  chalcedony 
  occurs 
  between 
  the 
  prisms 
  

   composing 
  the 
  Inoceramus-test. 
  It 
  would 
  appear 
  that 
  silicification 
  

   in 
  this 
  case 
  is 
  interprismatic, 
  and 
  not, 
  as 
  in 
  so 
  many 
  familiar 
  

   instances, 
  the 
  replacement 
  of 
  the 
  calcareous 
  prisms 
  themselves 
  by 
  

   silica. 
  These 
  results 
  throw 
  light 
  on 
  the 
  structures 
  obtained 
  by 
  

   me 
  in 
  the 
  Inoceramus 
  labiatus-zone 
  in 
  the 
  Isle 
  of 
  Wight, 
  1 
  which 
  

   at 
  the 
  time 
  were 
  doubtfully 
  referred 
  to 
  sponges, 
  but 
  are 
  evidently 
  

   identical 
  with 
  those 
  just 
  described. 
  

  

  Above 
  the 
  Inoceramus-h&nd 
  the 
  character 
  of 
  the 
  rock 
  remains 
  

   apparently 
  unaltered 
  for 
  a 
  thickness 
  of 
  about 
  2 
  feet, 
  but 
  in 
  its 
  

   upper 
  part 
  some 
  large 
  pelecypoda 
  were 
  observed, 
  lying 
  parallel 
  to 
  

   the 
  bedding, 
  and 
  all 
  on 
  the 
  same 
  horizon. 
  The 
  hardness 
  of 
  the 
  

   rock 
  prevented 
  their 
  extraction 
  in 
  fragments 
  sufficiently 
  large 
  for 
  

   identification, 
  but 
  the 
  appearance 
  suggested 
  a 
  form 
  of 
  Spondylus. 
  

  

  The 
  Chloritic 
  Chalk, 
  which 
  follows 
  next 
  in 
  succession, 
  is 
  

   a 
  pinkish 
  white 
  limestone, 
  about 
  4 
  feet 
  thick, 
  having 
  brown 
  nodules 
  

   from 
  1 
  inch 
  in 
  diameter 
  downward 
  scattered 
  through 
  it, 
  while 
  the 
  

   limestone 
  itself 
  is 
  dotted 
  with 
  green 
  grains 
  of 
  glauconite. 
  This 
  

   appears 
  to 
  be 
  the 
  equivalent 
  of 
  the 
  Spongiarian 
  zone 
  of 
  Tate, 
  and 
  

   is 
  characterized 
  by 
  the 
  presence 
  of 
  beautiful 
  internal 
  and 
  external 
  

   casts 
  of 
  many 
  foraminifera 
  and 
  sponge-spicules. 
  Prom 
  the 
  

   thicknesses 
  given 
  by 
  Tate 
  and 
  Barrois 
  it 
  would 
  appear 
  that 
  the 
  

   upper 
  part 
  of 
  this- 
  limestone 
  was 
  included 
  by 
  them 
  in 
  the 
  White 
  

   Limestone, 
  but 
  in 
  the 
  section 
  in 
  the 
  southern 
  glen, 
  where 
  the 
  

   Chloritic 
  Chalk 
  was 
  more 
  especially 
  studied, 
  no 
  direct 
  contact 
  with 
  

   the 
  latter 
  rock 
  (containing 
  Belemnitella 
  mucronaia) 
  was 
  observed 
  

   by 
  me. 
  

  

  In 
  the 
  upper 
  part 
  of 
  the 
  glen 
  the 
  White 
  Limestone 
  with 
  

   flints 
  is 
  well 
  displayed, 
  though 
  much 
  disturbed 
  by 
  the 
  intrusion 
  of 
  

   numerous 
  dykes 
  of 
  basalt. 
  The 
  chief 
  fossils 
  are 
  Belemnitella 
  

   mucronata, 
  Schloth., 
  and 
  Rliynclionella 
  octojplicata, 
  Sow. 
  

  

  1 
  ' 
  Chemical 
  and 
  Micro-Mineralogical 
  Researches 
  on 
  the 
  Upper 
  Cretaceous 
  

   Zones 
  of 
  the 
  South 
  of 
  England,' 
  London, 
  1893, 
  p. 
  48. 
  

  

  