﻿Geology. 
  233 
  

  

  the 
  authors 
  are, 
  it 
  is 
  one 
  of 
  the 
  best 
  state 
  reports 
  published 
  in 
  

   recent 
  years. 
  It 
  is 
  well 
  printed, 
  and 
  abundantly 
  illustrated 
  

   with 
  charts 
  and 
  maps, 
  photographs 
  of 
  rock 
  outcrops, 
  and 
  plates 
  

   of 
  fossils 
  illustrating 
  the 
  guide 
  species 
  for 
  the 
  various 
  formations 
  

   here 
  established. 
  The 
  Mississippian 
  system 
  includes 
  all 
  between 
  

   the 
  Devonian 
  and 
  Pennsylvania^ 
  and 
  it 
  is 
  only 
  here 
  and 
  there 
  

   that 
  a 
  hint 
  is 
  dropped 
  by 
  Ulrich 
  that 
  be 
  still 
  holds 
  to 
  his 
  

   "Waverlyan 
  and 
  Tennesseean 
  systems. 
  The 
  latter, 
  he 
  says, 
  "will 
  

   probably 
  be 
  ranked 
  as 
  a 
  system 
  comprising 
  three 
  coordinate 
  

   series, 
  the 
  Meramec 
  below, 
  the 
  Monte 
  Sana 
  in 
  the 
  middle, 
  and 
  

   the 
  Birdsville 
  above" 
  (p. 
  197). 
  The 
  Meramec 
  includes 
  the 
  

   "Warsaw, 
  Spergen, 
  and 
  St. 
  Louis 
  formations. 
  

  

  We 
  are 
  told 
  by 
  Butts 
  that 
  after 
  the 
  youngest 
  Mississippian 
  

   strata 
  of 
  Kentucky 
  and 
  Illinois 
  were 
  deposited 
  and 
  this 
  area 
  

   became 
  land, 
  the 
  last 
  of 
  the 
  Mississippian 
  sea 
  continued 
  farther 
  

   south 
  and 
  laid 
  down 
  in 
  Alabama 
  the 
  Parkwood 
  formation, 
  which 
  

   is 
  at 
  least 
  2000 
  feet 
  thick. 
  Then 
  followed 
  everywhere 
  a 
  land 
  

   interval 
  of 
  unknown 
  length, 
  and 
  when 
  the 
  Pottsvillian 
  sea 
  

   returned 
  to 
  the 
  Mississippi 
  valley 
  it 
  laid 
  down 
  in 
  Alabama 
  a 
  

   thickness 
  of 
  10,000 
  feet 
  of 
  strata 
  that 
  are 
  ' 
  ' 
  older 
  than 
  the 
  oldest 
  

   Pottsville 
  of 
  the 
  Mississippi 
  valley" 
  (118). 
  This 
  striking 
  state- 
  

   ment 
  again 
  brings 
  out 
  the 
  extraordinary 
  imperfection 
  of 
  the 
  

   geologic 
  record 
  and 
  warns 
  all 
  stratigraphers 
  to 
  consider 
  well 
  the 
  

   character 
  of 
  contacts 
  between 
  formations. 
  

  

  There 
  is 
  a 
  marked 
  difference 
  of 
  opinion 
  between 
  Ulrich 
  and 
  

   Weller 
  as 
  to 
  the 
  base 
  of 
  the 
  Chester, 
  and 
  in 
  regard 
  to 
  some 
  of 
  

   the 
  minor 
  correlations 
  as 
  well. 
  The 
  former 
  would 
  draw 
  the 
  bot- 
  

   tom 
  of 
  the 
  Chester 
  at 
  the 
  base 
  of 
  the 
  Ste, 
  Genevieve, 
  and 
  the 
  

   latter 
  at 
  the 
  top 
  of 
  the 
  same 
  formation. 
  Ulrich 
  remarks 
  that 
  

   "the 
  most 
  effective 
  and 
  the 
  most 
  widely 
  displayed 
  of 
  the 
  physical 
  

   breaks 
  in 
  the 
  upper 
  Mississippian 
  rocks 
  is 
  the 
  one 
  at 
  the 
  top 
  of 
  

   the 
  St. 
  Louis 
  limestone" 
  (191). 
  In 
  regard 
  to 
  this, 
  Butts 
  

   remarks 
  that 
  Ulrich 
  's 
  conclusions 
  can 
  apparently 
  only 
  be 
  refuted 
  

   "by 
  disproving 
  the 
  correctness 
  of 
  his 
  determination 
  of 
  fossil 
  

   forms" 
  (p. 
  86) 
  . 
  Ulrich, 
  to 
  establish 
  his 
  views, 
  finds 
  it 
  necessary 
  

   to 
  go 
  into 
  much 
  detail 
  regarding 
  the 
  fossils, 
  and 
  as 
  the 
  crinoids, 
  

   and 
  more 
  especially 
  the 
  pentremites, 
  are 
  the 
  stratigraphic 
  guides 
  

   mainly 
  relied 
  on, 
  he 
  describes 
  four 
  new 
  species 
  of 
  corals, 
  two 
  of 
  

   Dizygocrinus, 
  six 
  of 
  Talarocrinus, 
  twenty-two 
  of 
  Pentremites 
  

   (remarking, 
  however, 
  that 
  he 
  has 
  in 
  his 
  collection 
  discriminated 
  

   "over 
  100 
  species, 
  varieties, 
  and 
  mutations"), 
  and 
  one 
  brachi- 
  

   opod. 
  There 
  is 
  in 
  the 
  volume, 
  besides 
  this, 
  a 
  wealth 
  of 
  detailed 
  

   paleontology, 
  all 
  beautifully 
  illustrated. 
  

  

  "Marine 
  sedimentation," 
  says 
  Ulrich, 
  "was 
  not 
  continuous 
  

   through 
  the 
  Chester 
  epoch. 
  The 
  process 
  was 
  interrupted 
  at 
  

   least 
  five 
  times 
  before 
  the 
  final 
  withdrawal 
  of 
  the 
  Mississippian 
  

   sea. 
  Each 
  interruption 
  is 
  marked 
  by 
  evidence 
  of 
  partial 
  or 
  com- 
  

   plete 
  withdrawal 
  and 
  more 
  or 
  less 
  extensive 
  shifting 
  of 
  seas. 
  

  

  