﻿Fossils 
  in 
  strata 
  of 
  Carboniferous 
  Age. 
  97 
  

  

  majority 
  of 
  the 
  species 
  are 
  so 
  typically 
  Carboniferous 
  as 
  to 
  

   leave 
  no 
  doubt 
  of 
  their 
  Carboniferous 
  age. 
  

  

  In 
  describing 
  the 
  Lower 
  Carboniferous 
  fauna 
  of 
  the 
  Eureka 
  

   district 
  Mr. 
  Walcott 
  says 
  : 
  

  

  There 
  is 
  also 
  a 
  certain 
  commingling 
  of 
  upper 
  Devonian 
  species 
  

   with 
  the 
  lower 
  Carboniferous 
  fauna. 
  We 
  find 
  Discina 
  Newberryi, 
  

   Macrodon 
  Hamiltonia, 
  Grammysia 
  Hannibalensis, 
  G. 
  arcuata, 
  

   Sanguinolites 
  Aeolus, 
  Pleurotomaria 
  nodomarginata 
  associated 
  

   with 
  common 
  Carboniferous 
  species. 
  — 
  Pal. 
  Eureka 
  District, 
  p. 
  8. 
  

  

  The 
  same 
  commingling 
  of 
  species 
  is 
  noted 
  by 
  J. 
  P. 
  Smith.* 
  

   He 
  states 
  that 
  29 
  of 
  the 
  84 
  species 
  of 
  the 
  Baird 
  shales 
  of 
  

   Shasta 
  County, 
  California, 
  are 
  identical 
  with 
  the 
  

  

  forms 
  described 
  by 
  Walcott 
  from 
  the 
  lower 
  Carboniferous 
  of 
  the 
  

   Eureka 
  district, 
  and 
  in 
  this 
  Baird 
  shale 
  fauna 
  are 
  such 
  Carbonif- 
  

   erous 
  species 
  as 
  Produetus 
  Bnrlingtonensis, 
  P. 
  giganteus, 
  P. 
  JVe- 
  

   brascensis, 
  P. 
  punctatus 
  and 
  P. 
  semiretiadatus, 
  Spirifer 
  Uneatus 
  

   and 
  S. 
  striatus. 
  But 
  in 
  the 
  California 
  fauna 
  15 
  species 
  are 
  found 
  

   which 
  are 
  known 
  Devonian 
  fossils 
  of 
  Eastern 
  America. 
  

  

  In 
  my 
  manuscript 
  report 
  on 
  the 
  Arkansas 
  fauna 
  to 
  Dr. 
  

   Branner, 
  I 
  had 
  suggested 
  the 
  relationship 
  between 
  the 
  Spring 
  

   Creek 
  and 
  Eureka 
  faunas, 
  and 
  Mr. 
  Smith 
  who 
  had 
  read 
  it 
  

   before 
  writing 
  his 
  paper 
  on 
  the 
  Shasta 
  faunas 
  noticed 
  the 
  con- 
  

   firmation 
  his 
  species 
  furnished 
  of 
  this 
  interpretation. 
  The 
  

   Shasta 
  and 
  Eureka 
  faunas 
  find 
  an 
  unmistakable 
  representative 
  

   in 
  the 
  fauna 
  of 
  the 
  Spring 
  Creek 
  limestones 
  of 
  Arkansas, 
  and 
  

   the 
  fact 
  that 
  they 
  differ 
  from 
  the 
  ordinary 
  Carboniferous 
  

   faunas 
  of 
  the 
  Mississippi 
  Valley 
  in 
  the 
  particulars 
  which 
  asso- 
  

   ciate 
  them 
  with 
  these 
  faunas 
  west 
  of 
  the 
  Rocky 
  Mountains 
  is 
  

   a 
  strong 
  argument 
  for. 
  the 
  theory 
  that 
  this 
  Spring 
  Creek 
  fauna 
  

   migrated 
  into 
  the 
  seas 
  over 
  Arkansas 
  from 
  the 
  west, 
  was 
  there 
  

   only 
  temporarily 
  and 
  was 
  soon 
  withdrawn 
  or 
  destroyed, 
  leaving 
  

   only 
  this 
  solitary 
  record 
  of 
  its 
  existence 
  in 
  the 
  series 
  of 
  the 
  

   Mississippi 
  Valley. 
  Thus 
  all 
  the 
  evidence 
  in 
  hand 
  points 
  to 
  

   the 
  Carboniferous 
  age 
  of 
  the 
  Spring 
  Creek 
  limestone, 
  and 
  there 
  

   are 
  sufficient 
  reasons 
  for 
  referring 
  it 
  to 
  the 
  lower 
  third 
  of 
  the 
  

   Carboniferous 
  (the 
  Mississippian) 
  ; 
  and 
  its 
  correlation 
  with 
  an 
  

   horizon 
  about 
  equivalent 
  to 
  the 
  Warsaw, 
  St. 
  Louis, 
  or 
  the 
  

   Spergen 
  Hill 
  formations 
  is 
  strongly 
  suggested. 
  

  

  As 
  a 
  general 
  fauna, 
  this 
  Arkansas 
  'fauna 
  is 
  more 
  closely 
  allied 
  

   to 
  those 
  of 
  Eureka 
  District, 
  Nevada 
  and 
  of 
  Shasta 
  County, 
  

   California, 
  than 
  to 
  any 
  other 
  fauna 
  in 
  the 
  Mississippi 
  Valley 
  or 
  

   farther 
  east. 
  Both 
  of 
  these 
  western 
  faunas, 
  although 
  presenting 
  

   species 
  of 
  Devonian 
  type 
  commingled 
  with 
  the 
  Carboniferous 
  

   species 
  are 
  separated 
  by 
  considerable 
  thickness 
  of 
  strata 
  from 
  

  

  * 
  Journal 
  Geol., 
  vol. 
  ii, 
  p. 
  597. 
  

  

  Am. 
  Jour. 
  Sci.— 
  Third 
  Series, 
  Vol. 
  XLIX, 
  No. 
  290— 
  Feb., 
  1895. 
  

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