﻿364 
  PROCEEDINGS 
  OP 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Apr. 
  27, 
  

  

  spaces 
  are 
  empty. 
  Allowance 
  must 
  be 
  made 
  for 
  prefossil 
  wear 
  and 
  

   tear 
  in 
  increasing 
  the 
  dimensions 
  of 
  the 
  interspaces, 
  and 
  also 
  for 
  

   that 
  natural 
  thickening 
  of 
  the 
  walls, 
  which 
  tends 
  to 
  the 
  obliteration 
  

   of 
  interspaces 
  in 
  many 
  genera. 
  

  

  The 
  calcareous 
  form 
  of 
  fossilization 
  is 
  seen 
  to 
  the 
  greatest 
  advan- 
  

   tage 
  in 
  a 
  mass 
  of 
  shells 
  and 
  pieces 
  of 
  coral 
  from 
  the 
  coral-lime- 
  

   stone 
  of 
  Barbuda. 
  The 
  details 
  of 
  the 
  coral, 
  which 
  is 
  a 
  Cyphastraean, 
  

   are 
  well 
  preserved, 
  and 
  its 
  texture 
  is 
  very 
  dense 
  and 
  hard. 
  There 
  

   is 
  not 
  more 
  silica 
  in 
  the 
  specimen 
  than 
  is 
  usually 
  found 
  in 
  recent 
  

   corals. 
  

  

  In 
  a 
  specimen 
  of 
  the 
  same 
  species 
  from 
  the 
  Mvaje 
  shale 
  of 
  St. 
  

   Domingo, 
  this 
  form 
  of 
  calcareous 
  induration 
  is 
  well 
  seen 
  in 
  portions 
  

   of 
  the 
  mass, 
  but 
  not 
  on 
  the 
  calicular 
  surface. 
  The 
  density, 
  in- 
  

   creased 
  specific 
  gravity, 
  and 
  more 
  or 
  less 
  opaque-white 
  fracture 
  of 
  

   these 
  specimens 
  distinguish 
  them 
  from 
  recent 
  corals, 
  and 
  from 
  

   those 
  of 
  reefs 
  raised 
  during 
  the 
  existence 
  of 
  the 
  present 
  distribution 
  

   of 
  the 
  Zoantharia 
  in 
  the 
  West 
  Indies. 
  The 
  later 
  Tertiary 
  corals 
  of 
  

   the 
  Antilles 
  present 
  appearances 
  greatly 
  resembling 
  those 
  recently 
  

   dead, 
  but 
  generally 
  there 
  is 
  an 
  evident 
  gain 
  in 
  weight 
  and 
  hard- 
  

   ness. 
  This 
  form 
  is 
  not 
  found 
  in 
  the 
  Chert 
  and 
  lower 
  part 
  of 
  the 
  

   Marl 
  at 
  Antigua, 
  but 
  is 
  common 
  enough 
  at 
  St. 
  Domingo, 
  where 
  the 
  

   specimens 
  are 
  more 
  or 
  less 
  tinted 
  by 
  the 
  matrix, 
  and 
  have 
  generally 
  

   suffered 
  from 
  considerable 
  wear 
  and 
  tear. 
  

  

  The 
  impressions 
  of 
  calices 
  so 
  frequently 
  found, 
  consisting 
  of 
  in- 
  

   durated 
  matrix, 
  probably 
  result 
  from 
  the 
  disintegration 
  and 
  solu- 
  

   tion 
  of 
  the 
  calcareous 
  fossil 
  subsequently 
  to 
  the 
  hardening 
  of 
  the 
  

   beds. 
  The 
  second 
  variety 
  occurs 
  in 
  Jamaica, 
  at 
  Bowden, 
  where 
  

   crystalline 
  carbonate 
  of 
  lime 
  fills 
  up 
  the 
  interspaces 
  of 
  some 
  dendroid 
  

   corals. 
  

  

  2. 
  Siliceous. 
  Variety 
  1. 
  — 
  The 
  sclerenchyma 
  is 
  perfect; 
  it 
  con- 
  

   sists 
  of 
  homogeneous 
  silica, 
  which 
  is 
  generally 
  opaque 
  and 
  straw- 
  

   coloured 
  externally, 
  but 
  more 
  or 
  less 
  transparent 
  below 
  the 
  surface. 
  

   The 
  interspaces 
  are 
  empty. 
  

  

  Variety 
  2. 
  — 
  The 
  sclerenchyma 
  either 
  resembles 
  the 
  condition 
  of 
  

   the 
  first 
  variety, 
  or 
  it 
  may 
  be 
  more 
  or 
  less 
  of 
  a 
  transparent 
  grey 
  

   colour, 
  but 
  occasionally 
  the 
  silica 
  is 
  white 
  and 
  opaque. 
  The 
  inter- 
  

   spaces 
  are 
  filled 
  with 
  homogeneous, 
  transparent, 
  and 
  variously 
  

   coloured 
  silica. 
  

  

  Variety 
  3. 
  — 
  The 
  sclerenchyma 
  resembles 
  that 
  of 
  the 
  last 
  variety. 
  

   The 
  interspaces 
  are 
  either 
  filled 
  with 
  opaque 
  silica, 
  which 
  is 
  often 
  

   jasperoid, 
  opalescent, 
  and 
  porcellanous, 
  or 
  with 
  semi-opaque 
  silica, 
  

   whose 
  tints 
  are 
  red, 
  grey, 
  and 
  black. 
  

  

  Variety 
  4. 
  — 
  The 
  sclerenchyma 
  is 
  either 
  like 
  that 
  of 
  the 
  former 
  

   varieties, 
  or 
  it 
  is 
  much 
  coloured 
  by 
  the 
  former 
  influence 
  of 
  bitumen 
  

   and 
  salts 
  of 
  iron. 
  The 
  interspaces 
  are 
  here 
  and 
  there 
  empty. 
  

  

  The 
  first 
  \ariety 
  of 
  siliceous 
  fossilization, 
  where 
  the 
  coral, 
  instead 
  

   of 
  being 
  formed 
  of 
  its 
  usual 
  chemical 
  constituents, 
  consists 
  entirely 
  

   of 
  silica, 
  is 
  so 
  common 
  that 
  its 
  specimens 
  are 
  readily 
  distinguished 
  

   and 
  their 
  specific 
  affinities 
  easily 
  determined. 
  

  

  The 
  second 
  variety 
  constitutes 
  the 
  bulk 
  of 
  the 
  silicified 
  corals 
  of 
  

  

  