﻿206 
  EEPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  ones 
  west 
  and 
  north. 
  Prof. 
  Lesqnereux 
  says:* 
  "The 
  Lower 
  Lignitic 
  flora 
  

   has 
  Eot 
  as 
  yet 
  a 
  single 
  species 
  identical 
  with 
  any 
  of 
  the 
  Cretaceous, 
  and 
  ■ 
  

   even 
  very 
  few 
  have 
  a 
  distinct 
  relation 
  to 
  them." 
  So 
  far 
  as 
  the 
  value 
  of 
  

   palseontological 
  evidence 
  is 
  concerned, 
  I 
  should 
  give 
  preierence 
  to 
  in- 
  

   terpretations 
  derived 
  from 
  the 
  study 
  of 
  invertebrate 
  animals 
  and 
  plants, 
  

   over 
  those 
  based 
  upon 
  the 
  occurrence 
  of 
  vertebrates. 
  In 
  case 
  we 
  do 
  

   even 
  find 
  the 
  persistence 
  of 
  some 
  Cretaceous 
  types 
  carried 
  up 
  into 
  the 
  

   "Lignitic" 
  series, 
  this 
  will 
  prove 
  to 
  be 
  no 
  formidable 
  argument 
  in 
  favor 
  

   of 
  Cretaceous 
  age. 
  The 
  very 
  fact 
  of 
  having 
  but 
  an 
  imperfect 
  represen- 
  

   tation 
  of 
  the 
  entire 
  series 
  of 
  the 
  geological 
  groups 
  on 
  any 
  one 
  conti- 
  

   nent 
  has 
  given 
  rise 
  to 
  the 
  separation 
  into 
  conventional 
  " 
  formations." 
  

   Could 
  we 
  imagine 
  the 
  series 
  completed 
  and 
  every 
  missing 
  link 
  supplied 
  

   on 
  one 
  continent, 
  we 
  would 
  probably 
  be 
  still 
  less 
  able 
  than 
  now 
  to 
  ar- 
  

   range 
  and 
  place 
  every 
  formation 
  into 
  a 
  pigeon-hole 
  prepared 
  for 
  its 
  re- 
  

   ception. 
  So 
  far 
  as 
  I 
  am 
  able 
  to 
  judge, 
  we 
  have 
  in 
  the 
  case 
  of 
  tlie 
  "Lig- 
  

   nitic" 
  group, 
  (I 
  restrict 
  myself 
  to 
  speaking 
  of 
  Trinidad 
  and 
  Caiion, 
  

   where 
  I 
  have 
  made 
  personal 
  observations), 
  a 
  formation 
  analogous 
  to 
  

   the 
  "Wealden" 
  of 
  Europe. 
  For 
  a 
  long 
  time 
  there 
  was 
  much 
  doubt 
  as 
  

   to 
  the 
  position 
  of 
  the 
  latter 
  in 
  the 
  geological 
  scale, 
  until, 
  upon 
  palseon- 
  

   tological 
  and 
  lithological 
  evidence, 
  it 
  was 
  decided 
  to 
  be 
  Posi^-Jurassic 
  — 
  

   Pre 
  Cretaceous. 
  Taking 
  the 
  same 
  ground 
  with 
  reference 
  to 
  the 
  " 
  Lignitic" 
  

   group, 
  I 
  do 
  not 
  hesitate 
  to 
  call 
  it 
  Posf-Cretrweous^ 
  and 
  inasmuch 
  as 
  it 
  

   does 
  not 
  seem 
  to 
  have 
  sufficiently 
  well 
  developed 
  the 
  characteristics 
  that 
  

   we 
  require 
  of 
  our 
  ISTorth 
  American 
  Eocene, 
  I 
  call 
  it 
  Pre-Tertiary. 
  In 
  the 
  

   Keport 
  of 
  1873, 
  p. 
  349, 
  1 
  have 
  regarded 
  the 
  Coal-Measures 
  at 
  Caiion 
  

   as 
  a 
  "transition" 
  series, 
  and 
  I 
  find 
  additional 
  proof 
  of 
  the 
  position 
  there 
  

   taken, 
  in 
  the 
  region 
  of 
  Trinidad, 
  t 
  

  

  Professor 
  Stevenson 
  | 
  includes 
  the 
  Lignitic 
  beds 
  of 
  both 
  Canon 
  and 
  

   Trinidad 
  m 
  the 
  Cretaceous. 
  He 
  regards 
  them 
  merely 
  as 
  an 
  amplifica- 
  

   tion 
  of 
  Cretaceous 
  JSTo. 
  5, 
  laying 
  all 
  possible 
  stress 
  upon 
  the 
  "rusty 
  yel- 
  

   low 
  sandstone" 
  of 
  that 
  horizon. 
  He 
  states 
  (p. 
  25) 
  that 
  "in 
  Colorado 
  

   the 
  fossils 
  of 
  No. 
  5 
  are 
  usually 
  absent 
  from 
  the 
  lower 
  sandstones, 
  so 
  that 
  

   the 
  Lignitic 
  group 
  appears 
  to 
  rest 
  directly 
  upon 
  the 
  shales 
  of 
  the 
  Middle 
  

   Cretaceous." 
  With 
  the 
  exception 
  of 
  the 
  word 
  " 
  appears," 
  I 
  agree 
  in 
  this 
  

   with 
  Professor 
  Stevenson. 
  At 
  Trinidad 
  there 
  is 
  no 
  doubt 
  whatever 
  

   that 
  the 
  extensive 
  series 
  of 
  shales 
  and 
  sandstones 
  does 
  rest 
  " 
  directly 
  

   upon 
  the 
  shales 
  of 
  the 
  Middle 
  Cretaceous" 
  (Colorado 
  group). 
  From 
  

   these 
  latter 
  we 
  pass 
  up 
  through 
  a 
  characteristically 
  uniform 
  succession 
  

   of 
  strata, 
  until, 
  480 
  feet 
  above 
  the 
  shales, 
  we 
  find 
  the 
  first 
  coal. 
  Instead 
  

   of 
  assuming 
  that 
  the 
  fossils 
  of 
  Cretaceous 
  No. 
  5 
  are 
  "usually 
  absent 
  

   from 
  the 
  lower 
  sandstones," 
  I 
  have 
  come 
  to 
  the 
  conclusion 
  that 
  not 
  only 
  

   the 
  iossils, 
  but 
  No. 
  5 
  itself 
  is 
  absent. 
  It 
  is 
  scarcely 
  ever 
  possible 
  to 
  find 
  

   even 
  a 
  limited 
  district 
  where 
  some 
  member 
  of 
  the 
  " 
  standard" 
  succes- 
  

   sion 
  of 
  geological 
  strata 
  is 
  not 
  wanting. 
  Wherever, 
  then, 
  it 
  is 
  impossi- 
  

   ble 
  to 
  establish 
  beyond 
  a 
  doubt 
  the 
  existence 
  of 
  such 
  missing 
  stratum, 
  

   it 
  is 
  not 
  only 
  admissible, 
  but 
  necessary, 
  to 
  regard 
  the 
  succession 
  as 
  in- 
  

   conjplete. 
  All 
  the 
  more 
  is 
  this 
  the 
  case 
  when 
  we 
  have 
  (as 
  in 
  the 
  Trini- 
  

   dad 
  region) 
  an 
  area 
  of 
  more 
  than 
  700 
  square 
  miles 
  over 
  which 
  to 
  extend 
  

   our 
  investigations. 
  It 
  is 
  certainly 
  the 
  most 
  aggravating 
  obstinacy 
  in 
  a 
  

   sandstone 
  to 
  appear 
  over 
  so 
  large 
  an 
  extent 
  of 
  country, 
  unaccompanied 
  

   by 
  the 
  fossils 
  that 
  it 
  elsewhere 
  usually 
  carries. 
  

  

  In 
  the 
  Trinidad 
  region 
  I 
  consider 
  the 
  Cretaceous 
  members 
  above 
  the 
  

  

  * 
  United 
  HUtcs 
  Geolo!j;ical 
  Survey 
  Bulletin, 
  5, 
  II 
  ser., 
  187(5, 
  p. 
  243. 
  

   tCmiii'are 
  BuUetiu 
  United 
  States 
  Geological 
  Survey, 
  No. 
  5, 
  second 
  series, 
  January 
  

   8, 
  1H7(), 
  p. 
  402. 
  

   I 
  Paper 
  read 
  before 
  the 
  American 
  Phliosophical 
  Society 
  June 
  18, 
  1875. 
  

  

  