﻿176 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  of 
  the 
  adjoining 
  hill 
  lands. 
  The 
  upper 
  part 
  of 
  the 
  red 
  sands 
  

   grades 
  into 
  a 
  very 
  fertile 
  black 
  sandy 
  loam 
  showing 
  in 
  places 
  

   numerous 
  'specimens 
  of 
  Unionidce. 
  Caddo 
  prairie 
  occupies 
  the 
  

   highest 
  part 
  of 
  the 
  back 
  bottom 
  lands. 
  

  

  This 
  layer 
  of 
  black 
  sandy 
  loarn 
  with 
  JJyiios 
  appears 
  in 
  the 
  sides 
  

   of 
  the 
  bayous 
  in 
  several 
  places 
  in 
  the 
  bottoms, 
  commonly 
  over- 
  

   lying 
  the 
  same 
  poor 
  sands. 
  

  

  Age 
  of 
  the 
  beds. 
  — 
  The 
  exact 
  age 
  of 
  these 
  beds 
  can 
  only 
  be 
  a 
  

   matter 
  of 
  conjecture. 
  The 
  blue 
  clay 
  suggests 
  the 
  Port 
  Hudson 
  

   beds 
  of 
  Hilgard 
  and 
  the 
  spirited 
  discussion 
  of 
  the 
  age 
  of 
  the 
  blue 
  

   clay 
  of 
  the 
  Mississippi 
  bottoms. 
  In 
  this 
  region 
  some 
  of 
  the 
  blue 
  

   clay 
  is 
  clearly 
  part 
  of 
  the 
  adjoining 
  Eocene 
  formations, 
  as 
  at 
  the 
  

   rapids 
  at 
  Albany 
  flats 
  and 
  Big 
  Willow 
  pass. 
  

  

  The 
  poor 
  red 
  sands 
  may 
  represent 
  outliers 
  of 
  the 
  Eocene 
  hill 
  

   lands 
  or 
  may 
  belong 
  to 
  the 
  same 
  age 
  as 
  the 
  upland 
  flat 
  deposits. 
  

   Examples 
  of 
  unquestionably 
  erosion-formed 
  outliers 
  are 
  to 
  be 
  

   seen 
  in 
  several 
  places 
  in 
  the 
  bottoms. 
  Just 
  above 
  the 
  mouth 
  of 
  

   Black 
  Lake 
  bayou 
  are 
  two 
  mounds 
  which 
  are 
  merely 
  detached 
  

   portions 
  of 
  the 
  hill-lands. 
  Pine 
  island 
  in 
  Clear 
  lake 
  seems 
  to 
  be 
  

   of 
  the 
  same 
  class. 
  The 
  data 
  at 
  hand 
  are, 
  however, 
  at 
  present 
  a 
  

   little 
  too 
  meagre 
  to 
  admit 
  of 
  drawing 
  any 
  very 
  definite 
  con- 
  

   clusions 
  on 
  the 
  exact 
  age 
  of 
  the 
  sands. 
  

  

  Shells 
  from 
  the 
  front 
  land. 
  — 
  Some 
  of 
  the 
  light 
  yellowish-red 
  

   loam 
  which 
  occupies 
  the 
  immediate 
  banks 
  of 
  the 
  river 
  is 
  

   extremely 
  loess-like 
  in 
  texture 
  and 
  appearance. 
  The 
  resem- 
  

   blance 
  is 
  greatly 
  strengthened 
  by 
  the 
  presence 
  of 
  numerous 
  land 
  

   shells. 
  Mr. 
  C. 
  T. 
  Simpson, 
  of 
  the 
  U. 
  S. 
  National 
  Museum, 
  has 
  

   identified 
  the 
  following 
  species 
  from 
  Sec. 
  14, 
  19 
  N., 
  14 
  W. 
  : 
  

  

  Pyramidida 
  alternata, 
  Polygyra 
  palliata.f 
  

  

  Polygyra 
  thyroides. 
  Omphalina 
  friabilis. 
  

  

  Polygyra 
  clatisa. 
  Helicina 
  orbiculata. 
  

  

  Polygyra 
  inflecia. 
  

  

  To 
  this 
  list 
  of 
  species 
  Mr. 
  Simpson 
  has 
  added 
  : 
  " 
  We 
  do 
  not 
  

   have 
  any 
  of 
  the 
  Oinphalina 
  friabilis 
  quite 
  so 
  flat 
  as 
  the 
  species 
  

   you 
  send, 
  and 
  one 
  or 
  two 
  others 
  are 
  a 
  little 
  different 
  from 
  the 
  

   ordinary 
  manifestations 
  of 
  the 
  same 
  species. 
  P. 
  thyroides 
  as 
  sent 
  

   by 
  you 
  has 
  a 
  closed 
  umbicilicus 
  and 
  in 
  our 
  shells 
  it 
  is 
  open." 
  

  

  