﻿Hatcher 
  — 
  Sedimentary 
  Bocks 
  of 
  Southern 
  Patagonia. 
  101 
  

  

  and 
  Shell 
  Gap 
  and 
  other 
  places 
  on 
  the 
  Rio 
  Chico, 
  Lake 
  Pueyr- 
  

   redon, 
  about 
  the 
  sources 
  of 
  Desire 
  River, 
  and 
  at 
  various 
  places 
  

   in 
  the 
  valley 
  of 
  San 
  Julian. 
  A 
  study 
  of 
  the 
  collections 
  made 
  

   at 
  all 
  of 
  these 
  and 
  various 
  other 
  localities, 
  with 
  a 
  careful 
  regard 
  

   for 
  the 
  different 
  horizons 
  from 
  which 
  the 
  various 
  collections 
  

   were 
  made, 
  has 
  demonstrated 
  beyond 
  a 
  reasonable 
  doubt 
  the 
  

   identity 
  of 
  the 
  Patagonian 
  and 
  Supra- 
  Patagonian 
  beds, 
  

   which 
  do 
  not 
  represent 
  distinct 
  series 
  of 
  deposits 
  of 
  different 
  

   age, 
  but 
  only 
  different 
  phases 
  of 
  the 
  same 
  series 
  of 
  strata. 
  

   The 
  differences 
  in 
  the 
  fossils 
  and 
  lithological 
  characters 
  are 
  in 
  

   each 
  instance 
  due 
  to 
  the 
  local 
  conditions 
  attending 
  the 
  deposi- 
  

   tion 
  of 
  the 
  beds 
  at 
  the 
  various 
  localities 
  in 
  which 
  they 
  were 
  

   found. 
  The 
  Patagonian 
  beds 
  represent 
  areas 
  covered 
  by 
  

   deeper 
  waters, 
  while 
  the 
  Supra-Patagonian 
  beds 
  represent 
  the 
  

   shallow 
  water 
  and 
  littoral 
  deposits. 
  In 
  the 
  former 
  the 
  strata 
  

   are 
  more 
  continuous 
  and 
  the 
  rocks 
  composing 
  them 
  are 
  of 
  a 
  

   finer 
  grain 
  and 
  with 
  usually 
  more 
  calcareous 
  material, 
  while 
  

   in 
  the 
  Supra-Patagonian 
  phase 
  the 
  strata 
  of 
  sandstones, 
  clays, 
  

   etc. 
  replace 
  one 
  another 
  at 
  frequent 
  intervals 
  along 
  the 
  same 
  

   horizon, 
  and 
  are 
  largely 
  composed 
  of 
  coarse 
  sands 
  mingled 
  

   with 
  broken 
  and 
  ground 
  fragments 
  of 
  shells 
  in 
  great 
  abund- 
  

   ance, 
  frequently 
  forming 
  a 
  genuine 
  shell 
  breccia. 
  

  

  Dr. 
  Ameghino, 
  in 
  his 
  latest 
  contribution 
  on 
  the 
  geology 
  of 
  

   this 
  region, 
  has 
  not 
  only 
  separated 
  the 
  Supra-Patagonian 
  beds 
  

   from 
  the 
  Patagonian 
  beds, 
  but 
  has 
  also 
  divided 
  the 
  latter 
  into 
  

   two 
  formations, 
  a 
  lower 
  Piso 
  Juliense 
  and 
  an 
  upper 
  Piso 
  

   Leonense. 
  He 
  thus 
  has 
  represented 
  three 
  distinct 
  formations, 
  

   which 
  beginning 
  below 
  are 
  called 
  the 
  Juliense, 
  Leonense 
  and 
  

   Superpatagonica. 
  Under 
  each 
  of 
  these 
  he 
  gives 
  a 
  list 
  of 
  

   characteristic 
  invertebrates 
  as 
  follows: 
  

  

  Piso 
  Juliense. 
  — 
  Terebratula 
  patagonica 
  = 
  (Terebratella 
  p.). 
  

   Bouchardia 
  Zitteli, 
  Phynchonella 
  plicigera 
  = 
  (P. 
  nigricans), 
  

   Pecten 
  geminatus, 
  Pecten 
  praenuncius, 
  Siphonalia 
  noachina, 
  

   Hypechinus 
  patagonicus, 
  Echinarachinus 
  juliensis, 
  Schizaster 
  

   ameghinoi. 
  

  

  Piso 
  Leonense. 
  — 
  Ostrea 
  percrassa 
  = 
  (O. 
  ingens), 
  Perna 
  quad- 
  

   risulcata, 
  Cucullflea 
  alta, 
  Turritella 
  argentina, 
  Struthiolaria 
  

   ornata. 
  

  

  Superjyatagonica. 
  — 
  Ostrea 
  patagonica 
  = 
  (ingens, 
  non 
  d'Orb.), 
  

   Pecten 
  quemadensis 
  = 
  (P. 
  geminatus), 
  Cytherea 
  splendida, 
  

   Amathusia 
  angulata, 
  Voluta 
  ameghinoi, 
  Dentalium 
  octocos- 
  

   tatum. 
  

  

  Dr. 
  Ortmann, 
  who 
  has 
  studied 
  our 
  collections 
  of 
  Tertiary 
  

   invertebrates 
  from 
  Patagonia 
  and 
  finds 
  represented 
  in 
  them, 
  

   with 
  but 
  one 
  or 
  two 
  exceptions, 
  every 
  species 
  hitherto 
  reported 
  

   from 
  that 
  region 
  besides 
  many 
  additional 
  ones, 
  has 
  made 
  for 
  

   me 
  the 
  following 
  lists, 
  showing 
  the 
  association 
  which 
  he 
  has 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol 
  IX, 
  No. 
  50. 
  — 
  February, 
  1900. 
  

  

  