﻿90 
  Hatcher 
  — 
  Sedimentary 
  Rocks 
  of 
  Southern 
  Patagonia. 
  

  

  bottom 
  of 
  the 
  canon. 
  Thus 
  at 
  a 
  distance 
  of 
  only 
  two 
  or 
  three 
  

   hundred 
  yards 
  from 
  the 
  mouth 
  of 
  the 
  canon 
  the 
  top 
  of 
  the 
  

   Gio 
  beds 
  appears 
  at 
  and 
  passes 
  beneath 
  the 
  bed 
  of 
  the 
  stream. 
  

  

  Lower 
  Conglomerates. 
  — 
  The 
  Gio 
  beds 
  are 
  immediately 
  and 
  

   apparently 
  conformably 
  overlaid 
  by 
  about 
  20 
  feet 
  of 
  hard, 
  

   rather 
  fine 
  conglomerate, 
  which 
  will 
  be 
  designated 
  the 
  Lower 
  

   Conglomerate. 
  In 
  this 
  conglomerate 
  were 
  found 
  occasional 
  

   pieces 
  of 
  petrified 
  wood 
  filled 
  with 
  the 
  shells 
  of 
  small 
  bor- 
  

   ing 
  mollusca. 
  No 
  other 
  fossils 
  were 
  observed 
  in 
  this 
  con- 
  

   glomerate! 
  

  

  Belgrano 
  beds. 
  — 
  The 
  conglomerates 
  soon 
  disappear 
  beneath 
  

   the 
  bed 
  of 
  the 
  stream 
  and 
  are 
  seen 
  to 
  be 
  conformably 
  overlaid 
  

   by 
  about 
  300 
  feet 
  of 
  soft, 
  greenish 
  sandstones 
  and 
  clays, 
  

   replaced 
  toward 
  the 
  top 
  by 
  several 
  layers 
  of 
  harder 
  sandstones 
  

   and 
  impure 
  limestones, 
  each 
  usually 
  of 
  only 
  a 
  few 
  feet 
  in 
  

   thickness 
  and 
  appearing 
  as 
  ledges 
  projecting 
  from 
  the 
  side 
  of 
  

   the 
  canon. 
  These 
  300 
  feet 
  of 
  strata 
  we 
  shall 
  call 
  the 
  Belgrano 
  

   b&ds 
  from 
  Lake 
  and 
  Mt. 
  Belgrano, 
  located 
  some 
  distance 
  to 
  the 
  

   southward. 
  These 
  beds, 
  especially 
  toward 
  the 
  top 
  of 
  the 
  

   series, 
  are 
  rich 
  in 
  the 
  fossil 
  remains 
  of 
  characteristic 
  Mesozoic 
  

   invertebrates. 
  A 
  few 
  imperfect 
  plant 
  remains 
  were 
  also 
  

   found, 
  and 
  a 
  very 
  few 
  small, 
  trituberculate 
  teeth 
  were 
  dis- 
  

   covered 
  associated 
  in 
  the 
  same 
  rock 
  with 
  remains 
  of 
  Ammon- 
  

   ites. 
  These 
  trituberculate 
  teeth 
  may 
  perhaps 
  pertain 
  to 
  mam- 
  

   mals. 
  

  

  A 
  considerable 
  collection 
  of 
  invertebrates 
  was 
  made 
  from 
  

   the 
  Belgrano 
  beds 
  at 
  this 
  locality 
  and 
  from 
  another 
  exposure 
  

   of 
  the 
  same 
  beds 
  discovered 
  some 
  eight 
  miles 
  farther 
  east. 
  

   These 
  collections, 
  together 
  with 
  those 
  made 
  from 
  the 
  under- 
  

   lying 
  Lower 
  Conglomerate 
  and 
  Gio 
  beds, 
  have 
  been 
  placed 
  

   in 
  the 
  hands 
  of 
  Dr. 
  T. 
  W. 
  Stanton, 
  who 
  has 
  already 
  made 
  a 
  

   preliminary 
  study 
  of 
  them 
  and 
  writes 
  as 
  follows 
  : 
  " 
  Although 
  

   not 
  specifically 
  identified, 
  the 
  relationships 
  of 
  many 
  of 
  the 
  

   forms 
  are 
  such 
  that 
  there 
  is 
  no 
  doubt 
  of 
  their 
  Cretaceous 
  

   age, 
  and 
  I 
  am 
  at 
  present 
  inclined 
  to 
  place 
  them 
  not 
  earlier 
  

   than 
  about 
  the 
  middle 
  of 
  the 
  Cretaceous, 
  say 
  Gault 
  or 
  Ceno- 
  

   manian. 
  This 
  is 
  subject 
  to 
  revision, 
  however. 
  The 
  Trigonias 
  

   show 
  close 
  relationship 
  with 
  species 
  from 
  the 
  Uitenhage 
  beds 
  

   of 
  South 
  Africa, 
  which 
  I 
  believe 
  are 
  now 
  generally 
  assigned 
  to 
  

   the 
  Lower 
  Cretaceous." 
  The 
  Cretaceous 
  age 
  of 
  these 
  beds 
  as 
  

   determined 
  by 
  Stanton 
  from 
  a 
  study 
  of 
  the 
  invertebrate 
  collec- 
  

   tions 
  is 
  significant, 
  since 
  Dr. 
  Ameghino, 
  after 
  seeing 
  two 
  of 
  

   the 
  small 
  teeth 
  collected 
  by 
  myself 
  from 
  them, 
  immediately 
  

   referred 
  this 
  entire 
  series 
  of 
  beds 
  to 
  the 
  Jurassic* 
  

  

  * 
  See 
  Sinopsis 
  Geologica-Paleontologica 
  por 
  Florentine* 
  Ameghino 
  (En 
  

   Segundo 
  Censo 
  National 
  de 
  la 
  Republica 
  Argontina, 
  tomo 
  1, 
  pp. 
  111-255, 
  con 
  

   105 
  figs, 
  Buenos 
  Aires, 
  1898, 
  en 
  folio) 
  Supplemento 
  (Addiciones 
  y 
  Correcciones) 
  

   Julio 
  de 
  1899, 
  p. 
  13. 
  

  

  