﻿F. 
  H. 
  Knowlton 
  — 
  A 
  Dicotyledonous 
  Flora. 
  189 
  

  

  Aet. 
  XIV.— 
  A 
  Dicotyledonous 
  Flora 
  in 
  the 
  Type 
  Section 
  

   of 
  the 
  Morrison 
  Formation;* 
  by 
  F. 
  H. 
  Knowlton. 
  

  

  There 
  has 
  been 
  renewed 
  discussion 
  within 
  the 
  past 
  few 
  

   years 
  regarding 
  the 
  age 
  of 
  the 
  Morrison 
  formation, 
  that 
  

   is, 
  as 
  to 
  whether 
  it 
  should 
  be 
  placed 
  in 
  the 
  upper 
  part 
  of 
  

   the 
  Jurassic 
  or 
  in 
  the 
  overlying 
  Cretaceous. 
  The 
  diver- 
  

   gence 
  of 
  opinion 
  on 
  this 
  point 
  among 
  stratigraphers 
  

   and 
  paleontologists 
  was 
  well 
  brought 
  out 
  in 
  a 
  symposium 
  

   on 
  "The 
  close 
  of 
  Jurassic 
  and 
  opening 
  of 
  Cretaceous 
  

   time 
  in 
  North 
  America, 
  " 
  given 
  before 
  the 
  Paleontolog- 
  

   ical 
  Society 
  in 
  1914, 
  though 
  the 
  majority 
  opinion 
  among 
  

   those 
  who 
  participated 
  in 
  the 
  discussion 
  appeared 
  to 
  

   favor 
  placing 
  it 
  in 
  the 
  Cretaceous. 
  The 
  object 
  of 
  the 
  

   present 
  paper 
  is 
  to 
  present 
  some 
  recently 
  acquired 
  

   paleobotanical 
  evidence, 
  that, 
  if 
  correctly 
  interpreted, 
  

   seems 
  to 
  refer 
  the 
  upper 
  part 
  of 
  the 
  Morrison 
  formation 
  

   of 
  the 
  type 
  locality 
  definitely 
  to 
  the 
  Cretaceous, 
  and, 
  

   further, 
  to 
  place 
  it 
  much 
  higher 
  in 
  the 
  Cretaceous 
  than 
  

   has 
  been 
  thought 
  possible. 
  

  

  The 
  dicotyledonous 
  plants 
  to 
  be 
  considered 
  in 
  this 
  

   paper 
  were 
  collected 
  in 
  1916 
  by 
  W. 
  T. 
  Lee, 
  of 
  the 
  United 
  

   States 
  Geological 
  Survey. 
  They 
  came 
  from 
  the 
  type 
  

   section 
  of 
  the 
  Morrison 
  formation 
  at 
  Morrison, 
  Colo- 
  

   rado, 
  occurring 
  about 
  15 
  feet 
  below 
  the 
  top 
  of 
  the 
  forma- 
  

   tion 
  in 
  the 
  north 
  wall 
  of 
  the 
  so-called 
  gap 
  at 
  this 
  place. 
  

   The 
  matrix 
  bearing 
  the 
  plants 
  is 
  a 
  hard, 
  shaly, 
  somewhat 
  

   carbonaceous 
  sandstone. 
  

  

  In 
  view 
  of 
  the 
  fact 
  that 
  the 
  plants 
  here 
  described 
  are 
  

   of 
  a 
  type 
  not 
  before 
  known 
  to 
  occur 
  in 
  the 
  Morrison 
  

   formation, 
  it 
  is 
  naturally 
  of 
  the 
  utmost 
  importance 
  to 
  

   fix 
  their 
  position 
  definitely 
  with 
  reference 
  to 
  the 
  limits 
  

   of 
  the 
  type 
  section 
  of 
  this 
  formation. 
  Mr. 
  Lee 
  was 
  for- 
  

   tunate 
  in 
  having 
  with 
  him 
  on 
  the 
  occasion 
  of 
  his 
  visit 
  to 
  

   Morrison, 
  Mr. 
  George 
  L. 
  Cannon, 
  of 
  Denver, 
  who 
  not 
  

   only 
  assisted 
  in 
  excavating 
  many 
  of 
  the 
  dinosaurs 
  de- 
  

   scribed 
  by 
  Marsh 
  from 
  these 
  beds, 
  but 
  who 
  also 
  assisted 
  

   in 
  measuring 
  the 
  section 
  and 
  preparing 
  the 
  data 
  on 
  

   which 
  the 
  Morrison 
  formation 
  was 
  established. 
  He 
  

   pointed 
  out 
  to 
  Mr. 
  Lee 
  the 
  top 
  of 
  the 
  beds 
  as 
  originally 
  

   included 
  within 
  the 
  formation, 
  and 
  there 
  can, 
  therefore, 
  

   be 
  no 
  doubt 
  as 
  to 
  the 
  position 
  of 
  the 
  plant-bearing 
  layer, 
  

  

  * 
  Published 
  with 
  the 
  permission 
  of 
  the 
  Director 
  of 
  the 
  U. 
  S. 
  Geological 
  

   Society. 
  

  

  Am. 
  Jour. 
  Sci.— 
  Fourth 
  Series, 
  Vol. 
  XLIX, 
  No. 
  291.— 
  March, 
  1920. 
  

   14 
  

  

  