﻿AGE 
  OF 
  THE 
  TACONIC 
  SYSTEM. 
  405 
  

  

  greatly 
  the 
  range 
  of 
  localities 
  and 
  fossils. 
  The 
  species 
  include 
  well- 
  

   known 
  Trenton 
  Brachiopods 
  (OrtJiis 
  lynx, 
  O.pectinella, 
  ffliynchonella 
  

   capcuc, 
  Leptama 
  sericea, 
  Stropliomena 
  altemata) 
  and 
  Corals 
  (Petraia 
  

   corniculum), 
  the 
  Trenton 
  B-eceptaculites, 
  Crinoids, 
  Orthocerata, 
  and 
  

   Trilobites 
  (Illcmus 
  crassicauda). 
  But 
  besides 
  Trenton 
  species, 
  Prof. 
  

   Dwight 
  has 
  obtained 
  from 
  portions 
  of 
  this 
  same 
  limestone 
  belt 
  or 
  

   formation, 
  and 
  at 
  two 
  places 
  within 
  a 
  few 
  rods 
  of 
  Trenton 
  fossils, 
  

   fossils 
  of 
  the 
  Calciferous 
  group, 
  embracing 
  several 
  species 
  of 
  small 
  

   Orthocerata 
  (among 
  them 
  0. 
  ■primigenium) 
  and 
  of 
  Opliileta 
  (0. 
  com- 
  

   planata 
  and 
  0. 
  levata, 
  0. 
  (Maclurea) 
  sordida), 
  &c. 
  At 
  another 
  locality 
  

   in 
  the 
  continuation 
  of 
  the 
  limestone 
  west 
  of 
  the 
  Hudson, 
  the 
  Chazy 
  

   species 
  (Maclurea 
  magna) 
  has 
  been 
  found 
  by 
  the 
  palaeontologist, 
  

   Mr. 
  R. 
  P. 
  Whitfield. 
  

  

  It 
  has 
  thus 
  been 
  proved 
  that 
  the 
  western 
  of 
  the 
  limestones 
  asso- 
  

   ciated 
  with 
  the 
  Taconic 
  schists 
  (the 
  Sparry 
  limestone 
  of 
  Emmons) 
  

   consists, 
  to 
  the 
  south, 
  in 
  Dutchess 
  County, 
  of 
  the 
  combined 
  lime- 
  

   stones 
  of 
  the 
  Calciferous, 
  Chazy, 
  and 
  Trenton 
  eras, 
  just 
  as 
  it 
  does 
  

   to 
  the 
  north, 
  in 
  Vermont. 
  

  

  Less 
  than 
  a 
  year 
  before 
  this 
  discovery 
  of 
  fossils 
  in 
  the 
  limestones 
  

   of 
  the 
  Dutchess 
  County, 
  Mr. 
  T. 
  Nelson 
  Dale 
  had 
  announced 
  his 
  dis- 
  

   covery 
  of 
  related 
  fossils 
  in 
  the 
  hydromica-schists 
  adjoining 
  the 
  same 
  

   limestone 
  near 
  Poughkeepsie. 
  The 
  species 
  were 
  Orthis 
  testudinaria, 
  

   O.pectinella, 
  Leptama 
  sericea, 
  Strophomena 
  altemata, 
  and 
  remains 
  of 
  

   Crinoids 
  ; 
  and 
  Mr. 
  Dale 
  announced 
  the 
  schists 
  to 
  be 
  of 
  Hudson-river 
  

   age 
  or 
  newer 
  than 
  the 
  Trenton. 
  Both 
  these 
  Poughkeepsie 
  schists 
  and 
  

   the 
  associated 
  limestone 
  Prof. 
  Emmons 
  had 
  referred, 
  by 
  a 
  special 
  

   mention 
  of 
  the 
  locality, 
  to 
  his 
  Taconic 
  system. 
  

  

  The 
  discovery 
  of 
  fossils 
  in 
  the 
  limestone 
  was 
  a 
  natural 
  sequel 
  to 
  

   that 
  of 
  those 
  in 
  the 
  schist 
  ; 
  and 
  together 
  they 
  made 
  the 
  evidence 
  

   positive 
  that 
  the 
  limestone 
  and 
  schist 
  are 
  Lower 
  Silurian, 
  and 
  the 
  

   schist 
  the 
  younger 
  formation. 
  The 
  result 
  was 
  hence 
  reached 
  alike 
  

   from 
  the 
  rocks 
  from 
  the 
  southern 
  end 
  of 
  the 
  Taconic 
  belt 
  and 
  from 
  

   those 
  of 
  the 
  northern 
  or 
  Yermont 
  end. 
  It 
  is 
  sustained 
  in 
  both 
  

   regions 
  by 
  an 
  abundance 
  of 
  determinable 
  fossils 
  as 
  well 
  as 
  by 
  the 
  

   stratification. 
  If 
  Prof. 
  Emmons's 
  view 
  is 
  right 
  with 
  regard 
  to 
  the 
  

   western 
  and 
  eastern 
  limestones 
  and 
  the 
  intermediate 
  Taconic 
  schists 
  

   that 
  the 
  order 
  of 
  superposition 
  is 
  the 
  order 
  of 
  age, 
  then 
  the 
  western 
  

   is 
  the 
  oldest 
  of 
  the 
  three, 
  and 
  consequently 
  the 
  Taconic 
  schists 
  be- 
  

   neath 
  which 
  it 
  dips 
  are 
  younger 
  than 
  the 
  Trenton 
  schists, 
  inasmuch 
  

   as 
  the 
  western 
  limestone 
  is 
  partly 
  of 
  Trenton 
  age. 
  But 
  it 
  makes 
  

   the 
  eastern 
  limestone 
  younger 
  still, 
  or 
  a 
  part 
  of 
  the 
  Hudson-river 
  

   group. 
  

  

  Eacts 
  prove, 
  however, 
  that 
  the 
  eastern 
  and 
  western 
  limestones 
  are 
  

   the 
  same 
  formation 
  flexed 
  together, 
  and 
  that 
  this 
  limestone 
  forma- 
  

   tion 
  in 
  some 
  plain 
  cases 
  underlies 
  the 
  schists, 
  all 
  being 
  manifestly 
  in 
  

   a 
  broad 
  shallow 
  synclinal. 
  And 
  hence, 
  in 
  the 
  part 
  of 
  the 
  Taconic 
  

   range 
  having 
  only 
  eastward 
  dips, 
  the 
  probable 
  conclusion, 
  taking 
  

   into 
  view 
  all 
  the 
  facts 
  from 
  the 
  fossils, 
  is 
  that 
  the 
  beds 
  lie 
  in 
  general 
  

   in 
  a 
  closely 
  compressed 
  synclinal. 
  Eastward 
  dips, 
  as 
  has 
  been 
  re- 
  

   marked, 
  prevail 
  along 
  the 
  range 
  ; 
  the 
  broad 
  and 
  shallow 
  synclinals 
  

  

  Q. 
  J. 
  G. 
  S. 
  No. 
  151. 
  2 
  e 
  

  

  