﻿MUDGE.] 
  CRETACEOUS 
  — 
  DAKOTA. 
  • 
  291 
  

  

  and 
  Dakota 
  groups 
  have 
  been 
  collected 
  within 
  35 
  feet 
  vertically 
  and 
  

   one-half 
  mile 
  horizontally. 
  

  

  The 
  material 
  of 
  this 
  deposit 
  is 
  formed 
  very 
  largely 
  of 
  brown 
  and 
  varie- 
  

   gated 
  sandstone, 
  of 
  all 
  degrees 
  of 
  compactness, 
  from 
  that 
  which 
  crumbles 
  

   in 
  the 
  handling 
  to 
  that 
  which 
  requires 
  a 
  sledge-hammer 
  to 
  break 
  it; 
  

   This 
  extreme 
  hardness 
  is, 
  in 
  most 
  cases, 
  owing 
  to 
  the 
  presence 
  of 
  iron, 
  

   in 
  the 
  condition 
  of 
  oxide 
  and 
  silicates. 
  Sometimes 
  poor 
  limonite 
  is 
  seen. 
  

   In 
  some 
  places, 
  in 
  every 
  county 
  where 
  it 
  abounds, 
  it 
  affords 
  a 
  good 
  build- 
  

   ing-material. 
  It 
  is 
  frequently 
  interstratified 
  or 
  overlaid 
  by 
  clay-shales, 
  

   of 
  almost 
  all 
  colors. 
  Many 
  ledges 
  give 
  concretions 
  of 
  fanciful 
  forms, 
  

   sometimes 
  hollow, 
  or 
  with 
  the 
  center 
  filled 
  with 
  loose 
  sand. 
  Some 
  of 
  

   the 
  hollow 
  concretions 
  are 
  sufficiently 
  large 
  to 
  be 
  used 
  by 
  the 
  farmers 
  

   as 
  feeding-troughs 
  for 
  hogs 
  and 
  cattle. 
  In 
  a 
  few 
  localities 
  they 
  assume 
  

   the 
  form 
  of 
  tubes 
  of 
  various 
  sizes, 
  some 
  being 
  3 
  inches 
  in 
  diameter 
  and 
  

   3 
  to 
  8 
  feet 
  in 
  length. 
  These 
  concretionary 
  deposits 
  are 
  sometimes 
  glazed 
  

   and 
  distorted, 
  as 
  if 
  they 
  had 
  been 
  subject 
  to 
  the 
  action 
  of 
  fire 
  ; 
  but 
  the 
  

   cause 
  is 
  the 
  oxidation 
  of 
  iron, 
  and 
  not 
  any 
  application 
  of 
  heat. 
  Such 
  

   specimens 
  of 
  sandstone 
  frequently 
  inclose 
  well-preserved 
  dicotyledonous 
  

   leaves. 
  

  

  The 
  fossils 
  of 
  the 
  Dakota 
  consist 
  of 
  a 
  few 
  marine 
  mollusks, 
  some 
  few- 
  

   remains 
  of 
  fish 
  and 
  saurians, 
  but 
  it 
  is 
  more 
  particularly 
  noted 
  for 
  its 
  

   dicotyledonous 
  plants. 
  The 
  Molluscce 
  are 
  rare, 
  having 
  been 
  found 
  in 
  

   three 
  localities 
  only. 
  Two 
  of 
  these 
  are 
  in 
  the 
  western 
  part 
  of 
  Saline 
  

   County, 
  in 
  the 
  vicinity 
  of 
  Bavaria, 
  and 
  the 
  otber 
  is 
  in 
  the 
  western 
  por- 
  

   tion 
  of 
  Clay 
  County. 
  On 
  one 
  of 
  these 
  spots, 
  covering 
  not 
  over 
  two 
  

   acres, 
  we 
  procured 
  twelve 
  species, 
  new 
  to 
  science, 
  and 
  described 
  by 
  

   Prof. 
  F. 
  B. 
  Meek, 
  in 
  United 
  States 
  Geological 
  Survey, 
  Hayden, 
  1870, 
  

   pp. 
  297-313. 
  

  

  A 
  few 
  fish 
  and 
  one 
  saurian 
  {Ri/jjosaums 
  vehhii*) 
  have 
  been 
  found 
  in 
  

   this 
  group. 
  

  

  Of 
  the 
  fish, 
  the 
  most 
  interesting 
  is 
  the 
  Pelocorapis 
  rarius 
  Cope, 
  an 
  

   ally 
  of 
  the 
  flying-fish, 
  found 
  near 
  the 
  dividing 
  line 
  between 
  the 
  Dakota 
  

   and 
  Fort 
  Hays. 
  

  

  But 
  it 
  is 
  in 
  its 
  fossil 
  flora, 
  represented 
  largely 
  by 
  dicotyledonous 
  

   leaves, 
  that 
  the 
  Dakota 
  claims 
  the 
  attention 
  of 
  the 
  student 
  of 
  nature. 
  

   Professor 
  Lesquereux, 
  our 
  greatest 
  American 
  fossil 
  botanist, 
  has 
  devoted 
  

   to 
  this 
  flora 
  most 
  careful 
  and 
  valuable 
  study. 
  In 
  his 
  Cretaceous 
  Flora, 
  and 
  

   other 
  publications 
  connected 
  with 
  Professor 
  Hayden's 
  Geological 
  Sur- 
  

   vey, 
  he 
  has 
  given 
  us 
  the 
  results 
  of 
  many 
  years' 
  study, 
  to 
  which 
  we 
  refer 
  the 
  

   reader. 
  Professor 
  L. 
  says 
  : 
  " 
  The 
  plants 
  of 
  the 
  Dakota 
  group, 
  as 
  known 
  

   mostly 
  by 
  detached 
  leaves, 
  are 
  striking 
  by 
  the 
  beauty, 
  the 
  elegance, 
  the 
  

   variety 
  of 
  their 
  forms, 
  and 
  of 
  their 
  size. 
  In 
  all 
  this 
  they 
  are 
  fully 
  com- 
  

   parable 
  to 
  those 
  of 
  any 
  geological 
  epoch 
  as 
  well 
  as 
  those 
  of 
  our 
  time." 
  t 
  

  

  The 
  fossil 
  flora 
  is 
  almost 
  entirely 
  represented 
  by 
  leaves, 
  though 
  a 
  few 
  

   specimens 
  of 
  fi'uit, 
  imperfectly 
  preserved, 
  have 
  been 
  collected 
  ; 
  also 
  

   some 
  poor 
  fragments 
  of 
  wood 
  and 
  bark. 
  The 
  leaves, 
  however, 
  are 
  usu- 
  

   ally 
  in 
  excellent 
  preservation, 
  the 
  veins 
  and 
  veinlets 
  as 
  they 
  lie 
  imprint- 
  

   ed 
  on 
  the 
  stone 
  being 
  frequently 
  as 
  clearly 
  visible 
  in 
  all 
  their 
  outlines 
  

   as 
  those 
  just 
  taken 
  from 
  the 
  living 
  tree. 
  

  

  In 
  collecting 
  fossil 
  leaves 
  we 
  have 
  frequently 
  examined 
  every 
  visible 
  

   outcrop 
  for 
  15 
  or 
  20 
  miles 
  without 
  finding 
  a 
  specimen 
  ; 
  then 
  perhaps 
  a 
  

   single 
  square 
  mile 
  would 
  present 
  several 
  good 
  localities. 
  In 
  this 
  irreg- 
  

  

  " 
  See 
  Cope's 
  Cretaceous 
  Vertebrata, 
  p. 
  17, 
  where 
  this 
  specimen 
  is 
  incorrectly 
  stated 
  

   to 
  be 
  from 
  the 
  Niobrara. 
  Brookville, 
  the 
  locality 
  there 
  named, 
  is 
  clearly 
  on 
  the 
  

   Dakota. 
  

  

  t 
  Hayden's 
  Report, 
  1874, 
  p. 
  318. 
  

  

  