﻿96 
  Hatcher 
  — 
  Sedimentary 
  Rocks 
  of 
  Southern 
  Patagonia. 
  

  

  Tertiary 
  deposits 
  as 
  in 
  terst 
  ratified 
  with 
  the 
  Guaranitic 
  beds 
  

   and 
  Variegated 
  Sandstones 
  and 
  therefore 
  of 
  Cretaceous 
  age. 
  

   Formerly 
  Dr. 
  Ameghino 
  considered 
  all 
  of 
  such 
  Tertiary 
  

   deposits 
  as 
  of 
  one 
  age 
  and 
  belonging 
  to 
  one 
  series, 
  which 
  he 
  

   designated 
  as 
  the 
  Pyrotheriiun 
  beds. 
  In 
  my 
  former 
  paper 
  I 
  

   pointed 
  out 
  that 
  in 
  the 
  Pyrotherium 
  beds 
  of 
  Ameghino 
  there 
  

   were 
  represented 
  two 
  or 
  more 
  distinct 
  horizons. 
  I 
  at 
  the 
  same 
  

   time 
  suggested 
  that 
  some 
  of 
  the 
  fossil 
  mammals 
  described 
  by 
  

   Ameghino 
  as 
  from 
  the 
  Pyrotherium 
  beds 
  appeared 
  to 
  belong 
  

   to 
  a 
  formation 
  more 
  recent 
  than 
  the 
  Santa 
  Cruz 
  beds. 
  Further 
  

   explorations 
  in 
  Patagonia 
  have 
  only 
  confirmed 
  my 
  former 
  

   views 
  and 
  Dr. 
  Ameghino 
  has 
  since 
  partially 
  adopted 
  these 
  

   views. 
  He 
  has 
  now 
  divided 
  his 
  Pyrotherium 
  fauna 
  into 
  two 
  

   faunas, 
  referring 
  one 
  to 
  the 
  Middle 
  and 
  the 
  other 
  to 
  the 
  Upper 
  

   Cretaceous. 
  Unfortunately 
  he 
  has 
  not 
  yet 
  recognized 
  the 
  true 
  

   stratigraphic 
  position 
  of 
  the 
  beds 
  in 
  which 
  the 
  various 
  faunas 
  

   were 
  found 
  with 
  reference 
  to 
  the 
  Guaranitic 
  beds. 
  A 
  further 
  

   subdivison 
  of 
  this 
  Pyrotherium 
  fauna 
  is 
  necessary 
  and 
  a 
  recog- 
  

   nition 
  of 
  the 
  Miocene, 
  Pliocene 
  and 
  Pleistocene 
  nature 
  of 
  

   several 
  of 
  the 
  forms 
  included 
  in 
  it. 
  Among 
  such 
  Pleistocene 
  

   forms 
  will 
  be 
  found 
  the 
  large 
  gravigrade 
  edentate 
  described 
  by 
  

   Ameghino 
  as 
  not 
  distinguishable 
  from 
  Mylodon 
  and 
  more 
  than 
  

   likely 
  Pyrotherium, 
  which 
  resembles 
  very 
  closely 
  some 
  of 
  the 
  

   larger 
  Pleistocene 
  herbivorous 
  marsupials 
  of 
  Australia. 
  Un- 
  

   fortunately 
  I 
  have 
  not 
  as 
  yet 
  been 
  able 
  to 
  find 
  any 
  remains 
  of 
  

   Pyrotherium 
  and 
  have, 
  therefore, 
  been 
  unable 
  to 
  determine 
  its 
  

   exact 
  stratigraphic 
  position. 
  It 
  is 
  interesting 
  to 
  note, 
  however, 
  

   that 
  Dr. 
  Santiago 
  Roth, 
  who 
  has 
  spent 
  two 
  years 
  collecting 
  in 
  

   beds 
  which 
  according 
  to 
  Ameghino 
  contain 
  his 
  Pyrotherium 
  

   fauna, 
  has 
  not 
  found 
  a 
  single 
  fragment 
  of 
  Pyrotherium, 
  though 
  

   Ameghino 
  says 
  that 
  Pyrotherium 
  is 
  the 
  most 
  abundant 
  and 
  

   most 
  characteristic 
  fossil 
  in 
  the 
  beds. 
  Dr. 
  Roth 
  found 
  other 
  

   fossils 
  of 
  the 
  Pyrotherium 
  fauna 
  fairly 
  abundant. 
  

  

  The 
  Pyrotherium 
  beds, 
  as 
  that 
  term 
  has 
  been 
  used 
  by 
  Dr. 
  

   Ameghino, 
  includes 
  a 
  series 
  of 
  deposits 
  of 
  varying 
  age 
  from 
  

   Eocene 
  to 
  Pleistocene. 
  These 
  deposits 
  are 
  of 
  limited 
  area 
  and 
  

   usually 
  appear 
  as 
  yellow 
  or 
  ochre-colored 
  sands 
  and 
  clays 
  

   filling 
  depressions 
  eroded 
  in 
  the 
  surface 
  of 
  the 
  Guaranitic 
  

   beds 
  or 
  occasionally 
  of 
  the 
  Lower 
  Lignites 
  and 
  Variegated 
  

   Sandstones. 
  The 
  stratigraphic 
  relations 
  of 
  these 
  various 
  

   Tertiary 
  deposits 
  to 
  the 
  Dinosaur 
  and 
  other 
  Cretaceous 
  beds 
  of 
  

   Patagonia 
  are 
  the 
  same 
  as 
  the 
  relations 
  of 
  the 
  Equus 
  to 
  the 
  

   Loup 
  Fork 
  and 
  other 
  Tertiary 
  beds 
  in 
  our 
  western 
  States 
  ; 
  

   and 
  these 
  somewhat 
  obscure 
  stratigraphic 
  relations 
  have 
  led 
  to 
  

   the 
  same 
  confusion 
  regarding 
  the 
  age 
  and 
  fauna 
  of 
  each 
  that 
  

   formerly 
  existed 
  concerning 
  those 
  of 
  the 
  Equus 
  and 
  Loup 
  

   Fork 
  beds. 
  

  

  