﻿in 
  a 
  Section 
  of 
  the 
  Morrison 
  Formation. 
  191 
  

  

  ferred 
  without 
  question 
  to 
  the 
  Morrison 
  formation, 
  it 
  

   might 
  have 
  been 
  identified 
  as 
  a 
  Dakota 
  flora, 
  or 
  rather 
  

   with 
  that 
  from 
  the 
  so-called 
  Colorado 
  "Dakota." 
  These 
  

   plants 
  have 
  special 
  significance 
  because 
  they 
  came 
  from 
  

   the 
  type 
  Morrison 
  ; 
  because 
  they 
  are 
  biologically 
  higher 
  

   forms 
  than 
  have 
  heretofore 
  been 
  found 
  in 
  this 
  forma- 
  

   tion; 
  and 
  because 
  practically 
  only 
  two 
  localities 
  were 
  

   heretofore 
  known 
  to 
  have 
  afforded 
  Morrison 
  plant 
  re- 
  

   mains, 
  these 
  being 
  the 
  Freezeout 
  Hills, 
  Carbon 
  County, 
  

   Wyoming, 
  and 
  the 
  eastern 
  part 
  of 
  the 
  Bighorn 
  Basin, 
  

   Wyoming. 
  

  

  The 
  plants 
  from 
  the 
  Freezeout 
  Hills 
  comprise 
  23 
  spe- 
  

   cies, 
  two 
  of 
  which 
  are 
  based 
  on 
  coniferous 
  wood 
  and 
  the 
  

   others 
  on 
  silicified 
  trunks 
  of 
  cycads. 
  To 
  the 
  latter 
  Ward 
  

   gave 
  the 
  name 
  Cycadella, 
  but 
  according 
  to 
  Wieland 
  this 
  

   is 
  not 
  sufficiently 
  distinct 
  from 
  the 
  older 
  genus 
  Cyca- 
  

   deoidea. 
  

  

  The 
  plants 
  known 
  from 
  the 
  Bighorn 
  Basin 
  embrace 
  

   six 
  forms, 
  three 
  of 
  which 
  are 
  ferns, 
  one 
  an 
  equisetum, 
  

   and 
  two 
  are 
  cycads 
  based 
  on 
  foliage. 
  

  

  No 
  dicotyledons 
  have 
  been 
  found 
  in 
  either 
  locality, 
  and 
  

   there 
  is 
  ordinarily 
  no 
  hesitation 
  in 
  referring 
  both 
  the 
  

   Freezeout 
  Hills 
  and 
  Bighorn 
  Basin 
  floras 
  to 
  the 
  Lower 
  

   Cretaceous. 
  This 
  matter 
  will 
  be 
  referred 
  to 
  on 
  a 
  later 
  

   page. 
  

  

  The 
  type 
  section 
  of 
  the 
  original 
  Morrison 
  formation 
  

   has 
  a 
  thickness 
  of 
  about 
  300 
  feet 
  and 
  is 
  separated 
  from 
  

   the 
  overlying 
  beds 
  by 
  carbonaceous 
  material 
  which 
  has 
  

   the 
  appearance 
  of 
  being 
  a 
  fossil 
  soil. 
  These 
  overlying 
  

   beds 
  are 
  about 
  75 
  feet 
  thick 
  and 
  otherwise 
  have 
  been 
  

   interpreted 
  as 
  identical 
  with 
  beds 
  at 
  Colorado 
  Springs 
  

   and 
  Castle 
  Eock, 
  Colorado, 
  that 
  have 
  been 
  referred 
  to 
  

   the 
  Purgatoire 
  formation. 
  Above 
  the 
  so-called 
  Purga- 
  

   toire 
  formation 
  is 
  the 
  Dakota 
  sandstone 
  of 
  the 
  region. 
  

  

  Lee 
  made 
  a 
  small 
  collection 
  of 
  plants 
  in 
  the 
  presumed 
  

   Purgatoire 
  formation 
  at 
  Morrison 
  about 
  25 
  feet 
  above 
  

   its 
  base. 
  The 
  only 
  species 
  recognizable 
  is 
  Sapindus 
  

   morrisoni 
  Lesquereux, 
  a 
  form 
  well 
  known 
  in 
  the 
  Dakota 
  

   flora 
  of 
  the 
  Denver 
  Basin. 
  The 
  presence 
  of 
  plants 
  in 
  

   this 
  so-called 
  Purgatoire 
  formation 
  naturally 
  suggests 
  

   a 
  review 
  of 
  what 
  has 
  long 
  been 
  known 
  as 
  the 
  Dakota 
  

   flora 
  of 
  the 
  Denver 
  Basin, 
  especially 
  since, 
  according 
  to 
  

   Mr. 
  Cannon, 
  most 
  if 
  not 
  all 
  of 
  the 
  known 
  "Dakota 
  flora" 
  

   of 
  the 
  Denver 
  Basin 
  came 
  from 
  the 
  presumed 
  Purgatoire 
  

   formation 
  and 
  not 
  from 
  the 
  Dakota 
  as 
  now 
  recognized. 
  

  

  