﻿1)6 
  H. 
  S. 
  Williams 
  — 
  Recurrence 
  of 
  Devonian 
  

  

  ville 
  shales. 
  There 
  is 
  common 
  agreement 
  on 
  the 
  part 
  of 
  all 
  

   the 
  geologists 
  of 
  the 
  survey 
  who 
  have 
  studied 
  the 
  region 
  that 
  

   the 
  stratigraphical 
  position 
  of 
  the 
  Spring 
  Creek 
  limestone 
  

   is 
  between 
  the 
  Batesville 
  sandstone 
  (= 
  Chester-St. 
  Louis 
  

   horizon) 
  and 
  the 
  Boone 
  chert 
  (= 
  Keokuk-Burlington 
  horizon). 
  

  

  The 
  second 
  method 
  of 
  determination 
  is 
  by 
  identification 
  of 
  

   the 
  fauna 
  with 
  other 
  faunas 
  of 
  known 
  age. 
  The 
  general 
  

   Carboniferous 
  age 
  is 
  clearly 
  indicated 
  by 
  the 
  presence 
  of 
  

   Productus 
  of 
  the 
  types 
  of 
  cora 
  and 
  semireticulatus, 
  of 
  

   Spirifers 
  of 
  the 
  8. 
  bisulcatus 
  type 
  of 
  the 
  Carboniferous 
  

   limestone 
  of 
  England 
  and 
  elsewhere, 
  and 
  further 
  by 
  the 
  

   identity 
  of 
  several 
  of 
  the 
  species 
  with 
  those 
  in 
  the 
  neighbor- 
  

   ing 
  formation 
  containing 
  only 
  faunas 
  of 
  the 
  upper 
  forma- 
  

   tions 
  of 
  the 
  Mississippian 
  series 
  (" 
  Subcarboniferous' 
  1 
  ). 
  The 
  

   species 
  are 
  not 
  in 
  general 
  strictly 
  identical 
  with 
  species 
  of 
  any 
  

   of 
  the 
  typical 
  divisions 
  of 
  the 
  Mississippi 
  Valley 
  Carboniferous, 
  

   and 
  it 
  is 
  necessary 
  to 
  use 
  the 
  third 
  method 
  of 
  correlation 
  to 
  

   reach 
  greater 
  precision 
  than 
  a 
  general 
  correlation 
  with 
  faunas 
  

   of 
  neo- 
  Carboniferous 
  age. 
  

  

  According 
  to 
  the 
  third 
  method 
  we 
  compare 
  the 
  species 
  with 
  

   faunas 
  of 
  other 
  regions 
  whose 
  age 
  is 
  determined, 
  and 
  this 
  

   reveals 
  some 
  of 
  the 
  more 
  interesting 
  features 
  of 
  the 
  case. 
  

   Upon 
  making 
  close 
  identification 
  of 
  the 
  fauna 
  it 
  is 
  found 
  

   that 
  one 
  of 
  the 
  most 
  characteristic 
  and 
  abundant 
  species 
  in 
  the 
  

   fanna 
  of 
  the 
  Spring 
  Creek 
  limestone 
  is 
  identical 
  with 
  Walcott's 
  

   Rhynchonella 
  Eurekensis* 
  of 
  Lower 
  Carboniferous 
  lime- 
  

   stone 
  of 
  Secret 
  canon 
  road 
  Caiion 
  and 
  the 
  Caiion 
  of 
  Pinto 
  

   Park 
  of 
  Eureka 
  District, 
  Nevada. 
  This 
  is 
  a 
  unique 
  species, 
  

   no 
  Phynchonella 
  like 
  it 
  is 
  reported 
  from 
  North 
  America, 
  but 
  

   it 
  is 
  represented 
  by 
  several 
  European 
  species 
  from 
  Devonian 
  

   horizons, 
  or 
  more 
  ancient 
  (cf. 
  R. 
  Dumonti 
  Gosselet, 
  Devonian 
  

   of 
  Ardennes 
  ; 
  R. 
  princess 
  var. 
  Barrande 
  ; 
  R. 
  livonica 
  v. 
  

   Buch, 
  "Wenukoff, 
  Tab. 
  V, 
  fig. 
  3. 
  Russian 
  Devonian). 
  It 
  

   resembles 
  also 
  the 
  striated 
  varieties 
  of 
  the 
  recent 
  Rhy. 
  psit- 
  

   tacea. 
  Pleurotomaria 
  nodomarginata 
  McChesney, 
  referred 
  to 
  

   above, 
  or 
  a 
  very 
  closely 
  allied 
  form 
  is 
  among 
  the 
  Spring 
  Creek 
  

   species. 
  Walcott 
  identified 
  the 
  same 
  species 
  in 
  the 
  Secret 
  

   Cafion 
  road 
  Canon 
  locality 
  in 
  Nevada. 
  

  

  When 
  the 
  fauna 
  is 
  compared 
  with 
  the 
  fauna 
  of 
  Eureka 
  dis- 
  

   trict 
  three-fifths 
  of 
  the 
  genera 
  are 
  the 
  same, 
  and 
  many 
  of 
  the 
  

   species 
  closely 
  allied. 
  The 
  same 
  close 
  generic 
  resemblance 
  is 
  

   seen 
  on 
  comparing 
  the 
  former 
  with 
  the 
  Baird 
  shale 
  described 
  

   by 
  J. 
  P. 
  Smitlrf 
  from 
  the 
  TJ. 
  S. 
  Fisheries 
  in 
  Shasta 
  County, 
  

   California, 
  and 
  both 
  these 
  western 
  faunas 
  are 
  peculiar 
  in 
  hold- 
  

   ing 
  species 
  which 
  are 
  of 
  markedly 
  Devonian 
  type, 
  though 
  the 
  

  

  * 
  Monograph, 
  Paleontology 
  of 
  the 
  Eureka 
  District, 
  p. 
  223. 
  

   f 
  Journal 
  of 
  Geology, 
  vol, 
  ii, 
  Sept.-Oct., 
  1894, 
  p. 
  594. 
  

  

  