﻿

  Geology 
  and 
  Natural 
  History. 
  385 
  

  

  belong 
  to 
  the 
  Yale 
  collection. 
  The 
  remaining 
  eighteen 
  types 
  as 
  

   enumerated 
  below 
  are 
  the 
  property 
  of 
  the 
  University 
  of 
  Wyoming 
  

   at 
  Laramie. 
  

  

  The 
  discovery 
  of 
  these 
  cycads 
  by 
  W. 
  H. 
  Reed 
  and 
  their 
  Juras- 
  

   sic 
  age 
  was 
  first 
  announced 
  in 
  this 
  Journal 
  by 
  Prof. 
  O. 
  C. 
  

   Marsh 
  in 
  a 
  note 
  ou 
  " 
  Cycad 
  Horizons 
  in 
  the 
  Rocky 
  Mountains," 
  

   vol. 
  v, 
  p. 
  197, 
  Aug., 
  1898. 
  

  

  Professor 
  Wilbur 
  C. 
  Knight 
  is 
  also 
  quoted 
  as 
  follows 
  : 
  " 
  There 
  

   is 
  no 
  question 
  as 
  to 
  the 
  horizon 
  of 
  these 
  Cycads. 
  It 
  is 
  in 
  the 
  

   Jurassic 
  fresh-water 
  beds 
  and 
  near 
  the 
  bottom. 
  

  

  A 
  section 
  through 
  the 
  locality 
  of 
  the 
  cycad 
  beds 
  will 
  be 
  about 
  

   as 
  follows 
  : 
  

  

  Triassic 
  red 
  sandstone, 
  1000 
  feet. 
  

  

  Lower 
  Jurassic 
  (marine), 
  200 
  feet. 
  

  

  Upper 
  Jurassic 
  (fresh- 
  water), 
  225 
  feet. 
  

  

  Dakota 
  Conglomerate, 
  from 
  50 
  to 
  200 
  feet." 
  

  

  Further, 
  Professor 
  Ward 
  as 
  the 
  result 
  of 
  a 
  personal 
  visit 
  to 
  the 
  

   new 
  locality 
  confirms 
  the 
  previous 
  observations 
  on 
  its 
  strati- 
  

   graphical 
  position 
  as 
  follows 
  : 
  " 
  The 
  section 
  of 
  the 
  Freeze-Out 
  Hills 
  

   immediately 
  to 
  the 
  east 
  of 
  the 
  cycad 
  bed 
  and 
  including 
  the 
  ledges 
  

   formed 
  by 
  the 
  stratum 
  in 
  which 
  they 
  occur 
  was 
  carefully 
  meas- 
  

   ured. 
  It 
  is 
  a 
  characteristic 
  section 
  since 
  it 
  extends 
  from 
  the 
  Red 
  

   Beds 
  at 
  the 
  bottom 
  of 
  the 
  valley 
  to 
  the 
  Cretaceous 
  which 
  caps 
  

   the 
  hill 
  and 
  is 
  supposed 
  to 
  represent 
  the 
  Dakota 
  Group, 
  although 
  

   such 
  an 
  examination 
  of 
  it 
  as 
  I 
  was 
  able 
  to 
  make 
  led 
  me 
  to 
  sus- 
  

   pect 
  that 
  it 
  is 
  the 
  equivalent 
  of 
  the 
  Lower 
  Cretaceous 
  of 
  the 
  

   Black 
  Hills, 
  possibly 
  extending, 
  in 
  some 
  places, 
  to 
  the 
  true 
  

   Dakota 
  Group 
  of 
  Meek 
  and 
  Hayden. 
  

  

  The 
  following 
  is 
  the 
  section 
  : 
  

  

  Lower 
  Cretaceous 
  capping 
  the 
  hill 
  50 
  feet. 
  

  

  Base 
  of 
  Cretaceous 
  to 
  top 
  of 
  cycad 
  bed 
  100 
  " 
  

  

  Thickness 
  of 
  cycad 
  bed 
  ._.. 
  10 
  " 
  

  

  Bottom 
  of 
  cycad 
  bed 
  to 
  top 
  of 
  Marine 
  Jurassic 
  80 
  " 
  

  

  Thickness 
  of 
  Marine 
  Jurassic 
  to 
  bottom 
  of 
  valley 
  

  

  on 
  Red 
  Beds 
  115 
  " 
  

  

  Total 
  exposure 
  355 
  feet." 
  

  

  The 
  name 
  Cycadella 
  is 
  a 
  very 
  appropriate 
  one 
  for 
  this 
  new 
  

   series 
  of 
  pygmaic 
  species, 
  — 
  on 
  the 
  average 
  scarcely 
  a 
  tenth 
  the 
  

   size 
  of 
  the 
  trunks 
  from 
  the 
  Black 
  Hills. 
  The 
  generic 
  distinction 
  

   is 
  based 
  mainly 
  on 
  the 
  remarkable 
  development 
  of 
  a 
  secondary 
  

   ramentaceous 
  covering 
  of 
  the 
  trunks, 
  the 
  general 
  structure, 
  course 
  

   of 
  the 
  leaf 
  bundles 
  and 
  lateral 
  position 
  of 
  the 
  axes 
  of 
  fructification 
  

   being 
  otherwise 
  that 
  seen 
  in 
  the 
  genus 
  Gycadeoidea. 
  

  

  Professor 
  Ward 
  says 
  : 
  " 
  The 
  most 
  marked 
  feature 
  that 
  struck 
  

   me 
  on 
  first 
  casual 
  inspection 
  of 
  these 
  trunks, 
  aside 
  from 
  their 
  

   relatively 
  small 
  size, 
  light 
  color, 
  and 
  soft 
  calcareous 
  [silicifiedj 
  

   structure, 
  was 
  the 
  frequency 
  of 
  a 
  sort 
  of 
  smooth, 
  to 
  the 
  naked 
  

  

  