﻿Publications 
  of 
  Fl. 
  Ameghino. 
  263 
  

  

  two 
  very 
  different 
  faunas, 
  which 
  have 
  been 
  mixed 
  up 
  by 
  him, 
  

   because 
  the 
  beds 
  in 
  which 
  the 
  remains 
  were 
  found, 
  have 
  been 
  

   met 
  with 
  in 
  such 
  a 
  position 
  that 
  there 
  seemed 
  to 
  be 
  no 
  break 
  

   between 
  them. 
  Now 
  lie 
  has 
  found 
  them 
  separated 
  in 
  certain 
  

   localities, 
  and 
  lying 
  unconformably 
  to 
  each 
  other, 
  and 
  it 
  is 
  pos- 
  

   sible 
  to 
  recognize 
  two 
  faunas 
  separated 
  by 
  a 
  considerable 
  geo- 
  

   logical 
  interval. 
  The 
  true 
  Pyrotherium 
  fauna, 
  which 
  may 
  be 
  

   known 
  henceforth 
  by 
  this 
  name, 
  is 
  the 
  younger 
  and 
  belongs 
  to 
  

   the 
  Upper 
  Cretaceous, 
  while 
  the 
  older, 
  in 
  which 
  Pyrotherium 
  

   is 
  wanting 
  and 
  which 
  has 
  been 
  called 
  by 
  Carlos 
  the 
  Notosty- 
  

   lops 
  fauna, 
  belongs 
  to 
  the 
  Middle 
  Cretaceous." 
  

  

  This 
  new 
  version 
  does 
  not 
  agree 
  with 
  my 
  observations, 
  and 
  

   it 
  will 
  finally 
  be 
  shown 
  that 
  Pyrotherium 
  is 
  not 
  at 
  all 
  asso- 
  

   ciated 
  with 
  these 
  mammalian 
  remains. 
  The 
  other 
  genera, 
  

   which 
  he 
  designates 
  as 
  belonging 
  to 
  the 
  " 
  Pyrotherium 
  fauna 
  " 
  

   are 
  positively 
  not 
  from 
  those 
  Cretaceous 
  beds, 
  which 
  contain 
  

   the 
  remains 
  of 
  Mesozoic 
  Saurians, 
  but 
  belong 
  to 
  Tertiary 
  

   deposits, 
  and 
  have 
  nothing 
  to 
  do 
  with 
  the 
  Mesozoic 
  mammals 
  

   described 
  by 
  myself. 
  

  

  In 
  all 
  the 
  papers 
  in 
  which 
  Ameghino 
  treats 
  of 
  this 
  fauna, 
  he 
  

   states 
  that 
  remains 
  of 
  rodents 
  are 
  frequently 
  found 
  associated 
  

   with 
  it. 
  Among 
  the 
  mammalian 
  remains 
  discovered 
  by 
  myself 
  

   I 
  was 
  struck 
  by 
  the 
  complete 
  absence 
  of 
  rodents. 
  Although 
  I 
  

   have 
  found 
  this 
  fauna 
  again 
  on 
  my 
  last 
  trip 
  in 
  various 
  locali- 
  

   ties, 
  I 
  did 
  not 
  find 
  in 
  it 
  remains 
  of 
  a 
  single 
  rodent. 
  Of 
  course, 
  

   this 
  does 
  not 
  prove 
  that 
  rodents 
  are 
  entirely 
  wanting 
  in 
  this 
  

   fauna, 
  but 
  since 
  in 
  other 
  Mesozoic 
  deposits 
  no 
  rodents 
  have 
  

   been 
  discovered, 
  it 
  seems 
  very 
  probable 
  that 
  also 
  in 
  Patagonia 
  

   this 
  group 
  did 
  not 
  make 
  its 
  appearance 
  before 
  Tertiary 
  times. 
  

  

  2. 
  I 
  cannot 
  understand 
  what 
  Ameghino 
  means 
  by 
  his 
  " 
  Piso 
  

   Sehuense," 
  which, 
  with 
  the 
  Piso 
  Pehuenche 
  and 
  Pyrotheriense 
  

   is 
  said 
  to 
  constitute 
  his 
  Guaranitic 
  formation. 
  He 
  associates 
  in 
  

   this 
  stage 
  all 
  possible 
  deposits 
  which 
  are 
  mentioned 
  also 
  in 
  

   other 
  stages 
  : 
  for 
  instance, 
  he 
  says, 
  that 
  a 
  tufa-deposit 
  belongs 
  

   here, 
  in 
  which 
  I 
  have 
  found 
  associated 
  with 
  mammalian 
  

   remains 
  a 
  skull 
  of 
  a 
  species 
  of 
  Megalosaicrits. 
  The 
  mamma- 
  

   lian 
  remains, 
  he 
  alleges, 
  belong 
  to 
  the 
  Pyrotherium 
  fauna, 
  that 
  

   is 
  to 
  say, 
  to 
  the 
  Piso 
  Pyrotheriense, 
  but 
  the 
  skull 
  of 
  Megalo- 
  

   saurus 
  to 
  the 
  Piso 
  Sehuense! 
  For 
  this 
  skull 
  he 
  creates 
  a 
  new 
  

   genus, 
  Longosaurus 
  argentinus, 
  although 
  he 
  has 
  never 
  seen 
  it, 
  

   and 
  says 
  that 
  a 
  piece 
  of 
  a 
  femur 
  found 
  by 
  his 
  brother 
  near 
  Rio 
  

   Sehuen 
  belongs 
  to 
  the 
  same 
  species. 
  (The 
  skull 
  has 
  been 
  sent 
  

   to 
  London 
  for 
  determination.) 
  

  

  Further, 
  he 
  puts 
  into 
  this 
  stage 
  the 
  marine 
  deposit 
  discovered 
  

   by 
  me 
  near 
  Roca 
  on 
  the 
  Rio 
  iNegro, 
  and 
  says 
  that 
  the 
  same 
  is 
  

   found 
  well 
  developed 
  on 
  the 
  Li 
  may 
  and 
  Pichpicuru 
  Leufu, 
  as 
  

   well 
  as 
  on 
  the 
  Collon 
  Cura. 
  I 
  have 
  traveled 
  in 
  the 
  country 
  

  

  