﻿T. 
  E. 
  Savage 
  — 
  Devonian 
  Formation 
  of 
  Illinois. 
  173 
  

  

  ness 
  of 
  about 
  70 
  feet. 
  The 
  lower, 
  slialy 
  limestone 
  phase 
  

   of 
  the 
  Helderbergian 
  in 
  this 
  region 
  was 
  referred 
  to 
  by 
  

   Worthen 
  as 
  of 
  the 
  age 
  of 
  the 
  "Delthyris 
  slialy 
  lime- 
  

   stone, 
  " 
  but 
  no 
  separate 
  designation 
  was 
  applied 
  to 
  the 
  

   upper, 
  more 
  crystalline 
  limestone 
  member 
  of 
  the 
  Helder- 
  

   bergian 
  in 
  this 
  region. 
  

  

  Bailey 
  Limestone. 
  — 
  Ulrich 
  has 
  proposed 
  the 
  name 
  

   Bailey 
  limestone 
  for 
  the 
  lower, 
  cherty, 
  and 
  shaly 
  Helder- 
  

   bergian 
  strata 
  present 
  in 
  eastern 
  Missouri, 
  from 
  the 
  

   old 
  steamboat 
  landing 
  known 
  as 
  "Bailey's 
  landing,' 
  ' 
  

   where 
  Worthen 
  obtained 
  many 
  of 
  the 
  Helderbergian 
  fos- 
  

   sils 
  described 
  in 
  Volume 
  III 
  of 
  the 
  reports 
  of 
  the 
  Geo- 
  

   logical 
  Survey 
  of 
  Illinois. 
  This 
  name, 
  can 
  well 
  be 
  

   applied 
  to 
  the 
  corresponding 
  strata 
  in 
  Illinois. 
  The 
  

   characteristic 
  fossils 
  of 
  the 
  Bailey 
  limestone 
  are 
  Stro- 
  

   pheodonta 
  punctulifera, 
  Dalmanella 
  subcarinata, 
  Meris- 
  

   tella 
  Icevis 
  var., 
  Spirifer 
  cyclopterus, 
  S. 
  {Delthyris) 
  

   perlamellosus, 
  and 
  Dalmanites 
  palaceus. 
  

  

  "Back-hone" 
  Limestone. 
  — 
  The 
  upper 
  or 
  coarsely 
  crys- 
  

   talline 
  limestone 
  member 
  of 
  the 
  Helderbergian 
  is 
  well 
  

   exposed 
  near 
  the 
  south 
  end 
  of 
  the 
  Devil's 
  Back-bone 
  

   ridge, 
  a 
  short 
  distance 
  north 
  of 
  Grand 
  Tower, 
  in 
  Jack- 
  

   son 
  County, 
  Illinois, 
  and 
  it 
  is 
  proposed 
  to 
  designate 
  this 
  

   member 
  the 
  "Back-bone 
  limestone." 
  

  

  The 
  more 
  diagnostic 
  species 
  of 
  the 
  Back-bone 
  lime- 
  

   stone 
  are: 
  Aspidocrinus 
  scutelliformis, 
  Stropheodonta 
  

   hechii, 
  Oriskania 
  sinuata 
  var., 
  Spirifer 
  concinnus, 
  S, 
  

   (Delthyris) 
  cf. 
  perlamellosus, 
  and 
  Uncinulus 
  nucleolatus. 
  

   This 
  fauna 
  appears 
  to 
  be 
  closely 
  related 
  to 
  that 
  of 
  the 
  

   Becraft 
  limestone 
  of 
  the 
  New 
  York 
  section. 
  

  

  Oriskanian 
  Series. 
  

  

  No 
  rocks 
  of 
  Oriskanian 
  age 
  are 
  known 
  to 
  be 
  present 
  

   in 
  Illinois, 
  although 
  Weller 
  has 
  found 
  typical 
  Upper 
  

   Oriskany 
  rocks 
  farther 
  north 
  in 
  Ste. 
  Genevieve 
  County, 
  

   Missouri, 
  and 
  Dunbar 
  4 
  has 
  found 
  corresponding 
  Oris- 
  

   kany 
  strata 
  in 
  western 
  Tennessee 
  where 
  they 
  uncon- 
  

   formably 
  underlie 
  the 
  Camden 
  chert. 
  It 
  seems 
  certain 
  

   that 
  these 
  Oriskany 
  strata 
  were 
  originally 
  deposited 
  in 
  

   southern 
  Illinois, 
  between 
  the 
  Missouri 
  and 
  Tennessee 
  

   localities, 
  but 
  they 
  were 
  largely 
  removed 
  by 
  erosion 
  in 
  

   this 
  intr 
  -^ening 
  area 
  before 
  the 
  earliest 
  of 
  the 
  Middle 
  

  

  4 
  Dunbar, 
  (\ 
  U.: 
  this 
  Journal 
  (4), 
  46, 
  746-749, 
  1918. 
  

   Am. 
  Jour. 
  Sci.— 
  Fourth 
  Series, 
  Vol. 
  XLIX, 
  No. 
  291.— 
  March, 
  1920. 
  

   13 
  

  

  