﻿Keyes 
  — 
  Carboniferous 
  and 
  Devonian 
  Strata. 
  163 
  

  

  by 
  Udden.* 
  They 
  are 
  not 
  a 
  local 
  development 
  of 
  uncertain 
  

   affinities 
  as 
  stated 
  by 
  Calvin 
  ;f 
  nor 
  do 
  they 
  underlie 
  the 
  Lime 
  

   Creek 
  shales 
  as 
  indicated 
  in 
  his 
  general 
  geologic 
  section 
  of 
  

   Iowa.J 
  It 
  appears 
  that 
  Owen 
  and 
  Norwood§ 
  in 
  drawing 
  the 
  

   line 
  of 
  separation 
  of 
  the 
  Devonian 
  and 
  Carboniferous 
  strata 
  in 
  

   the 
  Mississippi 
  valley 
  at 
  the 
  black 
  shale, 
  displayed 
  phenomen- 
  

   ally 
  keen 
  insight 
  into 
  the 
  real 
  geologic 
  succession 
  in 
  the 
  

   region. 
  

  

  Particularly 
  noteworthy 
  the 
  Burlington 
  section 
  remains. 
  

   When 
  discussing 
  the 
  Devonian 
  Interval 
  in 
  Missouri! 
  I 
  was 
  

   inclined 
  to 
  regard 
  the 
  entire 
  shale-section 
  between 
  the 
  Cedar 
  

   limestone 
  and 
  the 
  Chouteau 
  limestone 
  as 
  a 
  distinct 
  unit, 
  

   Devonian 
  in 
  age, 
  and 
  having 
  intercalated 
  the 
  lens 
  of 
  Louisiana 
  

   limestone. 
  This 
  conclusion 
  was 
  based 
  largely 
  upon 
  faunal 
  

   grounds 
  and 
  especially 
  upon 
  the 
  Gomphoceras 
  fauna 
  then 
  

   newly 
  found 
  high 
  up 
  in 
  the 
  section 
  at 
  Burlington, 
  and 
  after- 
  

   wards 
  especially 
  noted 
  by 
  Weller.^f" 
  This 
  fauna 
  was 
  discovered 
  

   by 
  me 
  at 
  the 
  time 
  that 
  the 
  report 
  on 
  Des 
  Moines 
  county 
  was 
  

   being 
  printed 
  ;** 
  and 
  six 
  years 
  later 
  the 
  fossils 
  were 
  turned 
  

   over 
  by 
  Dr. 
  Calvin 
  to 
  Professor 
  Weller 
  for 
  critical 
  examina- 
  

   tion. 
  As 
  a 
  result 
  Weller 
  was 
  led 
  to 
  correlateff 
  the 
  lithographic 
  

   limestone 
  (bed 
  4) 
  of 
  the 
  Chouteau 
  formation, 
  at 
  Burlington, 
  

   with 
  the 
  Louisiana 
  limestone 
  at 
  the 
  typical 
  locality, 
  and 
  to 
  

   regard 
  the 
  fossils 
  of 
  the 
  shales 
  as 
  constituting 
  the 
  oldest 
  

   Kinder 
  hook 
  fauna. 
  

  

  Stratigraphically 
  there 
  seems 
  to 
  be 
  no 
  doubt 
  whatever 
  that 
  

   Bed 
  4: 
  at 
  Burlington 
  cannot 
  possibly 
  be 
  the 
  continuation 
  of 
  

   the 
  Louisiana 
  limestone. 
  Yet 
  there 
  is 
  really 
  no 
  serious 
  faunal 
  

   discrepancy 
  in 
  Weller's 
  determinations. 
  That 
  the 
  older 
  fauna 
  

   — 
  a 
  fauna 
  of 
  marked 
  Devonian 
  aspects 
  — 
  should 
  occur 
  at 
  a 
  

   stratigraphic 
  horizon 
  higher 
  than 
  that 
  of 
  the 
  Louisiana 
  lime- 
  

   stone 
  is 
  not 
  remarkable. 
  It 
  is 
  easily 
  explained. 
  At 
  Burling- 
  

   ton 
  the 
  shale 
  succession 
  from 
  the 
  Grassy 
  formation 
  to 
  the 
  

   Chouteau 
  limestone 
  is 
  uninterrupted 
  ; 
  at 
  Louisiana 
  a 
  thick 
  

   limestone 
  divides 
  the 
  shales. 
  In 
  the 
  north 
  the 
  fauna 
  of 
  the 
  

   Grassy 
  black 
  shales 
  continued 
  upward 
  unbroken. 
  The 
  Gom- 
  

   phoceras 
  fauna 
  from 
  the 
  shales 
  40 
  feet 
  below 
  the 
  Burlington 
  

   limestone 
  at 
  Burlington 
  is 
  probably 
  the 
  characteristic 
  fauna 
  of 
  

   the 
  Hannibal 
  shales, 
  although 
  the 
  latter 
  at 
  the 
  typical 
  locality 
  

   have 
  thus 
  far 
  proved 
  unfossiliferous. 
  

  

  *Iowa 
  Geol. 
  Surv., 
  vol. 
  ix, 
  p. 
  301, 
  1899. 
  

   f 
  Journal 
  of 
  Geology, 
  vol. 
  xiv, 
  p. 
  572, 
  1906. 
  

   jlowa 
  Geol. 
  Surv., 
  vol. 
  xvii, 
  p. 
  192, 
  1907. 
  

  

  § 
  Researches 
  on 
  the 
  Protozoic 
  and 
  Carboniferous 
  Eocks 
  of 
  Central 
  Ken- 
  

   tucky 
  during 
  the 
  year 
  1846, 
  1847. 
  

  

  I 
  Bull. 
  Geol. 
  Soc. 
  America, 
  vol. 
  xiii, 
  p. 
  267, 
  1902. 
  

   IT 
  Iowa 
  Geol. 
  Surv., 
  vol. 
  x, 
  p. 
  69, 
  1900. 
  

   **Ibid., 
  vol. 
  iii, 
  p. 
  433, 
  1895. 
  

   ft 
  Ibid., 
  vol. 
  x, 
  p. 
  70, 
  1900. 
  

  

  