﻿106 
  Hatcher 
  — 
  Sedimentary 
  Rocks 
  of 
  Southern 
  Patagonia. 
  

  

  the 
  beginning 
  of 
  the 
  deposition 
  of 
  the 
  Santa 
  Cruz 
  beds. 
  

   About 
  this 
  time 
  the 
  gradual 
  subsidence 
  which 
  had 
  been 
  going 
  on 
  

   during 
  the 
  deposition 
  of 
  the 
  former 
  series, 
  became 
  less 
  rapid 
  

   or 
  ceased 
  altogether, 
  and 
  the 
  shallow 
  sea 
  in 
  which 
  those 
  rocks 
  

   were 
  being 
  deposited 
  was 
  converted 
  into 
  lowlands 
  and 
  estu- 
  

   aries 
  which 
  were 
  at 
  once 
  invaded 
  by 
  the 
  herds 
  of 
  animals 
  

   inhabiting 
  the 
  adjacent 
  lands, 
  or 
  others 
  more 
  distant, 
  with 
  

   which 
  communications 
  were 
  then 
  established. 
  The 
  remarka- 
  

   bly 
  rich 
  mammalian 
  fauna 
  that 
  at 
  that 
  time 
  inhabited 
  this 
  region 
  

   has 
  left 
  its 
  remains 
  in 
  great 
  abundance 
  and 
  often 
  in 
  a 
  remarka- 
  

   bly 
  good 
  state 
  of 
  preservation 
  in 
  the 
  sandstones 
  and 
  clays 
  of 
  

   the 
  Santa 
  Cruz 
  beds. 
  Scarcely 
  a 
  foot 
  of 
  this 
  entire 
  1,500 
  feet 
  

   of 
  sediment 
  that 
  is 
  not 
  fossiliferons, 
  and 
  seldom 
  an 
  exposure, 
  

   however 
  small 
  in 
  area, 
  that 
  will 
  not 
  yield 
  a 
  jaw 
  or 
  skull 
  as 
  a 
  

   reward 
  for 
  even 
  a 
  superficial 
  search. 
  It 
  is 
  not 
  to 
  be 
  under- 
  

   stood 
  that 
  these 
  deposits 
  are 
  everywhere 
  equally 
  rich 
  in 
  fossils, 
  

   for 
  like 
  all 
  other 
  fossil 
  fields, 
  some 
  localities 
  are 
  rich 
  and 
  some 
  

   poor 
  according 
  as 
  were 
  the 
  conditions 
  during 
  the 
  deposition 
  of 
  

   the 
  sediment 
  favorable 
  or 
  not 
  for 
  the 
  accumulation 
  and 
  pres- 
  

   ervation 
  of 
  animal 
  remains. 
  

  

  Notwithstanding 
  the 
  remarkable 
  similarity 
  of 
  the 
  rocks 
  

   forming 
  the 
  Santa 
  Cruz 
  beds 
  in 
  the 
  many 
  exposures 
  through- 
  

   out 
  their 
  great 
  geographical 
  extent, 
  it 
  is 
  evident 
  that 
  they 
  were 
  

   not 
  deposited 
  in 
  an 
  open 
  fresh-water 
  lake 
  nor 
  in 
  a 
  broad 
  shal- 
  

   low 
  sea 
  of 
  salt 
  water. 
  Not 
  only 
  are 
  they 
  in 
  their 
  typical 
  

   development 
  remarkably 
  barren 
  of 
  the 
  remains 
  of 
  either 
  fresh 
  

   or 
  salt 
  water 
  invertebrates, 
  but 
  they 
  contain 
  the 
  remains 
  of 
  

   land 
  mammals 
  in 
  such 
  abundance 
  that 
  it 
  is 
  absolutely 
  impossi- 
  

   ble 
  to 
  conceive 
  of 
  these 
  remains 
  having 
  been 
  conveyed 
  bodily 
  

   into 
  the 
  middle 
  of 
  a 
  great 
  lake 
  or 
  ocean 
  hundreds 
  of 
  miles 
  in 
  

   breadth. 
  So 
  far 
  as 
  is 
  at 
  present 
  known, 
  not 
  a 
  single 
  mollusk 
  

   shell, 
  or 
  fish, 
  or 
  crocodile 
  bone 
  or 
  tooth 
  has 
  been 
  found 
  any- 
  

   where 
  in 
  the 
  true 
  Santa 
  Cruz 
  beds 
  ; 
  although 
  many 
  of 
  the 
  

   strata 
  are 
  well 
  adapted 
  for 
  the 
  preservation 
  of 
  the 
  remains 
  of 
  

   such 
  animals, 
  had 
  they 
  existed 
  in 
  any 
  considerable 
  numbers, 
  as 
  

   would 
  undoubtedly 
  have 
  been 
  the 
  case 
  had 
  this 
  region 
  been 
  

   covered 
  during 
  the 
  period 
  of 
  their 
  deposition 
  by 
  a 
  great 
  lake 
  

   or 
  other 
  continuous 
  body 
  of 
  water. 
  Not 
  only 
  are 
  the 
  remains 
  

   of 
  land 
  mammals 
  abundant 
  in 
  many 
  exposures, 
  but 
  in 
  some 
  

   instances 
  the 
  positions 
  in 
  which 
  the 
  skeletons 
  are 
  found 
  are 
  

   such 
  as 
  suggest 
  that 
  the 
  animals 
  lived 
  and 
  died 
  in 
  the 
  immedi- 
  

   ate 
  neighborhood 
  where 
  their 
  remains 
  now 
  lie 
  entombed. 
  

  

  One 
  of 
  the 
  best 
  localities 
  for 
  the 
  collector 
  of 
  vertebrate 
  fos- 
  

   sils 
  to 
  be 
  found 
  anywhere 
  in 
  Patagonia 
  is 
  on 
  the 
  beach 
  laid 
  

   bare 
  at 
  low 
  tide 
  along 
  the 
  Atlantic 
  coast 
  between 
  Coy 
  Inlet 
  

   and 
  Cape 
  Fairweather. 
  On 
  this 
  beach 
  the 
  erosion 
  accomplished 
  

   by 
  the 
  rise 
  and 
  fall 
  of 
  the 
  tides, 
  which 
  here 
  have 
  a 
  maximum 
  

  

  