﻿

  the 
  Trenton 
  fauna, 
  then 
  nVmriahing 
  in 
  

   lv 
  w 
  * 
  rotinental 
  platfonn. 
  During 
  the 
  Utica 
  

  

  1 
  »' 
  '•'•• 
  '"u,i 
  bearing 
  current* 
  encroached 
  on 
  the 
  eastern 
  part 
  

   atinent 
  and 
  drove 
  oo1 
  a 
  part 
  of 
  the 
  Trenton 
  fauna. 
  1 
  

  

  ,>J> 
  B8IO» 
  OF 
  THE 
  VALIDITY 
  OF 
  THE 
  TEBM, 
  « 
  HUD- 
  

  

  BOM 
  RIVEB 
  GROUP" 
  

  

  T,n 
  * 
  demonntnU 
  the 
  presence 
  of 
  Trenton, 
  Utica 
  and 
  Lor- 
  

  

  raine 
  faunas 
  in 
  the 
  shales 
  of 
  the 
  Hudson 
  river 
  valley, 
  necessitates 
  

   newed 
  investigation 
  of 
  the 
  validity 
  of 
  the 
  old 
  term. 
  « 
  Hudson 
  

   river 
  group", 
  or 
  its 
  modification, 
  - 
  Hudson 
  group", 
  as 
  proposed 
  

   by 
  Walcott 
  for 
  all 
  the 
  beds 
  between 
  the 
  Trenton 
  limestone 
  and 
  

   the 
  Dipper 
  Sitoic. 
  As 
  the 
  term 
  has 
  been 
  so 
  ably 
  and 
  forcibly 
  

   defended 
  by 
  such 
  authoril 
  Hal] 
  (17) 
  and 
  Walcott 
  (36a), 
  its 
  

  

  a 
  n 
  be 
  question 
  ed 
  only 
  after 
  obtaining 
  new 
  facts. 
  These, 
  

  

  A 
  parallel 
  o 
  the 
  continued 
  appearance 
  of 
  genera 
  in 
  the 
  Quebec 
  

  

  Uograptna 
  shale* 
  and 
  the 
  conglomerate 
  of 
  Rysedorph 
  hill 
  which 
  hare 
  

   l 
  In 
  homotaxlal 
  beda 
  of 
  other 
  regions 
  of 
  eastern 
  North 
  Vmerica 
  

   Damnation 
  of 
  Trenton 
  form, 
  which 
  nowhere 
  else 
  have 
  been 
  ob-' 
  

  

  the 
  Trenton, 
  as 
  P 
  a 
  r 
  a 
  b 
  t 
  ro 
  p 
  h 
  i 
  a 
  . 
  h 
  e 
  m 
  1 
  pi 
  icat 
  a 
  

  

  P*ra 
  bianlcata, 
  Clionychia 
  undata 
  Spyro- 
  

  

  bilineatnm, 
  Cyrtoceraa 
  annulatum, 
  Crypto- 
  

  

  tricornis. 
  and 
  C 
  1 
  1 
  macograp 
  t 
  u 
  a 
  caudatua, 
  

  

  the 
  general 
  character 
  of 
  their 
  fossil 
  contents 
  are 
  char- 
  

  

  benomenon 
  has 
  been 
  observed 
  in 
  

  

  locallttea, 
  at 
  the 
  Dudley 
  observatorv 
  bv 
  Dr 
  Beecher 
  In 
  

  

  ps 
  on 
  Green 
  [aland, 
  one 
  on 
  Van 
  Schalck 
  island, 
  and 
  ' 
  one 
  

  

  Ule 
  by 
  the 
  writer. 
  The 
  .beds 
  near 
  Mechanicsville 
  

  

  winded 
  aa 
  being 
  evidently 
  transitional 
  between 
  the 
  Tren- 
  

  

  age, 
  but 
  the 
  other 
  beda 
  lie 
  at 
  or 
  

  

  Dttca 
  terrane 
  and 
  yet 
  contain 
  Trenton 
  forms 
  .till 
  

  

  : 
  ' 
  i,y 
  ta 
  *•«» 
  aof 
  the 
  I 
  • 
  . 
  to 
  the 
  writefa 
  

  

  to 
  the 
  Hudson 
  valley 
  region, 
  and 
  therefore, 
  marks 
  a 
  

  

  character 
  of 
  the 
  Dtica 
  fannaa. 
  ] 
  lc 
  lualon 
  

  

  not 
  Oorynoldea 
  cnrtna 
  m.-ntloned 
  

  

  1 
  **** 
  to 
  the 
  Utica 
  beda 
  of 
  the 
  middle 
  

  

  it 
  tills 
  the 
  beds 
  of 
  the 
  lower 
  Mohawk 
  and 
  the 
  

  

  shale 
  iust 
  above 
  the 
  Tren- 
  

  

  1 
  amplaln. 
  alao 
  the 
  variety 
  of 
  Plec- 
  

  

  l 
  •erlcea 
  with 
  wrinkled 
  cardinal 
  margin, 
  mentioned 
  

  

  ■vhich 
  extends 
  in 
  this 
  region 
  from 
  the 
  loweet 
  Trenton 
  

  

  1 
  is 
  rarely 
  observed 
  outside 
  of 
  it 
  

  

  