﻿424 
  Twenhofel 
  — 
  Wreford 
  and 
  Foraker 
  Limestones. 
  t 
  

  

  Fusulina 
  had 
  a 
  similar 
  habitat. 
  If 
  this 
  were 
  true, 
  they 
  

   could 
  hardly 
  have 
  dropped 
  into 
  the 
  coagulating 
  masses 
  

   of 
  silica, 
  and, 
  if 
  these 
  were 
  rolled 
  around 
  on 
  the 
  sea 
  bot- 
  

   tom, 
  some 
  sort 
  of 
  banded 
  arrangement 
  in 
  their 
  distribu- 
  

   tion 
  in 
  the 
  nodules 
  ought 
  to 
  have 
  developed. 
  As 
  these 
  

   cherts 
  are 
  little 
  banded, 
  the 
  implication 
  would 
  be 
  that 
  

   they 
  had 
  not 
  been 
  rolled 
  about 
  ; 
  such 
  being 
  the 
  case, 
  the 
  

   Fusulinas 
  must 
  have 
  dropped 
  into, 
  or 
  crawled 
  upon, 
  the 
  

   " 
  gel-masses.'' 
  If 
  they 
  lived 
  on 
  the 
  bottom 
  the 
  former 
  

   was 
  not 
  possible. 
  If 
  the 
  Fusulinas 
  were 
  indeed 
  pelagic 
  in 
  

   habitat 
  and 
  fell 
  upon 
  the 
  coagulated 
  chert, 
  or 
  were 
  bot- 
  

   tom-dwellers 
  and 
  crawled 
  upon 
  it, 
  it 
  would 
  seem 
  that 
  the 
  

   long 
  axes 
  of 
  the 
  tests 
  would 
  be 
  tangent 
  to 
  the 
  upper 
  sur- 
  

   face 
  or 
  sides 
  of 
  the 
  "gel." 
  Such, 
  however, 
  is 
  not 
  the 
  

   case, 
  as 
  the 
  axes 
  of 
  these 
  shells 
  are 
  oriented 
  in 
  every 
  pos- 
  

   sible 
  direction. 
  

  

  For 
  the 
  basal 
  chert 
  of 
  the 
  Wreford 
  — 
  that 
  in 
  which 
  the 
  

   chert 
  occurs 
  only 
  as 
  a 
  replacement 
  of 
  the 
  shells 
  of 
  organ- 
  

   isms 
  — 
  the 
  explanation 
  of 
  original 
  precipitation 
  has 
  no 
  

   application. 
  These 
  are 
  obviously 
  replacements. 
  

  

  The 
  second 
  chert 
  of 
  the 
  Wreford, 
  in 
  which 
  there 
  is 
  the 
  

   intricate 
  intergrowth 
  of 
  limestone 
  and 
  chert, 
  is 
  also 
  diffi- 
  

   cult 
  to 
  explain 
  on 
  the 
  theory 
  of 
  original 
  precipitation. 
  

   These 
  cherts 
  do 
  not 
  have 
  an 
  elliptical 
  globular 
  shape, 
  and 
  

   to 
  the 
  writer 
  it 
  does 
  not 
  appear 
  possible 
  that 
  the 
  intricate 
  

   intermingling 
  of 
  the 
  limestone 
  and 
  the 
  chert 
  could 
  have 
  

   developed 
  through 
  the 
  confluence 
  of 
  any 
  number 
  of 
  coag- 
  

   ulated 
  globular 
  or 
  elliptical 
  masses 
  of 
  silica, 
  since 
  the 
  

   chert 
  has 
  ramifications 
  in 
  every 
  direction 
  which 
  are 
  con- 
  

   fluent 
  with 
  neighboring 
  masses 
  laterally 
  and 
  vertically 
  

   and 
  has 
  all 
  sorts 
  of 
  projections 
  and 
  embayments. 
  Fur- 
  

   thermore, 
  the 
  sponge 
  spicules 
  which 
  are 
  present 
  in 
  this 
  

   chert 
  offer 
  difficulty. 
  It 
  is 
  possible 
  that 
  they 
  might 
  have 
  

   floated 
  to 
  the 
  masses 
  and 
  adhered 
  to 
  them 
  and 
  subse- 
  

   quently 
  been 
  covered 
  by 
  more 
  silica. 
  Three 
  thin 
  sections 
  

   made 
  from 
  the 
  associated 
  limestone 
  where 
  it 
  occurs 
  in 
  

   the 
  same 
  block 
  from 
  which 
  a 
  thin 
  section 
  of 
  the 
  chert 
  was 
  

   made, 
  and 
  within 
  one 
  and 
  six 
  inches 
  of 
  the 
  place 
  where 
  

   the 
  fragment 
  for 
  the 
  thin 
  section 
  of 
  chert 
  was 
  derived, 
  

   do 
  not 
  show 
  a 
  single 
  thing 
  which 
  can 
  be 
  positively 
  identi- 
  

   fied 
  as 
  a 
  sponge 
  snicule, 
  although 
  other 
  fossils 
  are 
  pres- 
  

   ent. 
  It 
  may 
  be 
  that 
  sponge 
  spicules 
  were 
  once 
  present 
  

   in 
  the 
  limestone 
  and 
  have 
  been 
  dissolved, 
  otherwise 
  there 
  

   must 
  have 
  been 
  some 
  selective 
  action 
  of 
  the 
  objects 
  to 
  

  

  