﻿180 
  T. 
  E. 
  Savage 
  — 
  Devonian 
  Formation 
  of 
  Illinois. 
  

  

  cies 
  of 
  fossils 
  all 
  of 
  which 
  are 
  similar 
  to 
  those 
  present 
  

   in 
  the 
  younger 
  Lime 
  Creek 
  shale 
  farther 
  north 
  in 
  Floyd 
  

   and 
  Cerro 
  Gordo 
  comities, 
  Iowa, 
  and 
  are 
  not 
  known 
  at 
  

   so 
  low 
  a 
  horizon 
  in 
  any 
  other 
  locality. 
  Several 
  years 
  

   ago 
  this 
  dark 
  fossiliferous 
  shale 
  was 
  thrown 
  ont 
  in 
  dig- 
  

   ging 
  a 
  well 
  on 
  the 
  floor 
  of 
  a 
  quarry 
  near 
  Independence, 
  

   Iowa. 
  It 
  has 
  not 
  been 
  seen 
  in 
  natural 
  exposures, 
  nor 
  

   has 
  it 
  been 
  certainly 
  recognized 
  in 
  well 
  records 
  at 
  this 
  

   horizon 
  in 
  other 
  places. 
  It 
  is 
  believed 
  by 
  the 
  writer, 
  

   who 
  had 
  the 
  privilege 
  of 
  visiting 
  the 
  locality 
  with 
  Pro- 
  

   fessor 
  Calvin 
  and 
  collecting 
  some 
  of 
  the 
  fossils 
  from 
  the 
  

   old 
  dump, 
  that 
  this 
  shale 
  came 
  from 
  a 
  pocket 
  of 
  Lime 
  

   Creek 
  shale 
  that 
  at 
  this 
  place 
  had 
  sifted 
  down 
  through 
  

   an 
  open 
  joint 
  or 
  fissure 
  and 
  filled 
  a 
  small 
  cavern 
  in 
  the 
  

   Wapsipinicon 
  limestone, 
  just 
  as 
  Pottsville 
  sands 
  and 
  

   clays 
  are 
  often 
  found 
  filling 
  fissures 
  and 
  caverns 
  in 
  the 
  

   Devonian 
  limestone 
  in 
  the 
  vicinity 
  of 
  Rock 
  Island. 
  

   This 
  would 
  indicate 
  that 
  originally 
  the 
  Lime 
  Creek 
  shale 
  

   extended 
  southward 
  at 
  least 
  as 
  far 
  as 
  Independence, 
  

   Iowa, 
  but 
  no 
  rocks 
  of 
  this 
  age 
  are 
  known 
  in 
  Illinois. 
  

  

  In 
  Linn 
  County, 
  Iowa, 
  Norton 
  has 
  described 
  the 
  Otis 
  

   member 
  of 
  the 
  Wapsipinicon 
  limestone 
  below 
  the 
  hori- 
  

   zon 
  of 
  the 
  Independence 
  shale, 
  which 
  is 
  thought 
  to 
  cor- 
  

   respond 
  with 
  the 
  limestone 
  containing 
  numerous 
  shells 
  

   of 
  Spirifer 
  subumbonus 
  exposed 
  on 
  Campbells 
  island 
  in 
  

   the 
  Mississippi 
  river 
  north 
  of 
  Moline. 
  

  

  Cedar 
  Valley 
  Limestone. 
  — 
  The 
  Cedar 
  Valley 
  lime- 
  

   stone, 
  which 
  overlies 
  the 
  "Wapsipinicon 
  limestone 
  in 
  

   apparent 
  conformity, 
  consists 
  of 
  somewhat 
  shaly, 
  ob- 
  

   liquely 
  jointed 
  limestone 
  in 
  the 
  lower 
  part, 
  and 
  contains 
  

   the 
  Acervularia 
  davidsoni 
  coral 
  reef 
  near 
  the 
  middle. 
  

   In 
  the 
  upper 
  part 
  the 
  strata 
  consist 
  of 
  gray 
  limestone 
  

   which 
  at 
  certain 
  levels 
  is 
  composed 
  largely 
  of 
  spherical 
  

   and 
  flattened 
  stromatoporoids. 
  The 
  total 
  thickness 
  of 
  

   this 
  limestone 
  is 
  about 
  100 
  feet. 
  The 
  characteristic 
  fos- 
  

   sils 
  of 
  the 
  lower 
  part 
  of 
  the 
  Cedar 
  Valley 
  limestone 
  are 
  

   AstrcEospongia 
  hamiltonensis, 
  Phillip 
  •sastraea 
  billingsi, 
  

   Acervularia 
  profunda, 
  Spirifer 
  aspera, 
  S. 
  bimesialis, 
  S. 
  

   iowensis, 
  and 
  S. 
  subundiferus. 
  The 
  middle 
  portion 
  

   includes 
  the 
  coral 
  reef 
  horizon, 
  and 
  contains 
  the 
  fossils 
  

   Acervularia 
  davidsoni, 
  Favosites 
  alpenensis, 
  Cladopora 
  

   iowensis, 
  Striatopora 
  rugosa 
  and 
  Spirifer 
  parryanus. 
  

   In 
  the 
  upper 
  layers 
  occur 
  Pentamerella 
  micula, 
  Dielasma 
  

   iowense, 
  and 
  Straparollus 
  cyclostomus. 
  The 
  writer 
  has 
  

  

  