﻿52 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  been 
  currently 
  correlated 
  with 
  the 
  " 
  Hudson 
  River," 
  Lorraine 
  or 
  

   Frankfort 
  formations, 
  mainly 
  for 
  the 
  reason 
  that 
  they 
  overlie 
  the 
  

   black 
  (Canajoharie) 
  shales, 
  which 
  were 
  identified 
  with 
  the 
  Utica 
  

   shale 
  ; 
  further 
  because 
  they 
  are 
  lithologically 
  like 
  the 
  Lorraine 
  beds 
  ; 
  

   and, 
  finally, 
  because 
  they 
  seem 
  to 
  be 
  continuous 
  westward 
  with 
  the 
  

   Frankfort 
  shale, 
  the 
  lower 
  division 
  of 
  the 
  Lorraine 
  group 
  as 
  it 
  was 
  

   hitherto 
  understood. 
  Recent 
  investigations 
  by 
  the 
  writer 
  1 
  have, 
  

   however, 
  shown 
  that 
  this 
  thick 
  formation 
  contains 
  a 
  fauna 
  not 
  

   younger 
  than 
  Trenton, 
  that 
  the 
  underlying 
  black 
  shale 
  is 
  not 
  Utica 
  

   but 
  early 
  Trenton 
  in 
  age, 
  and 
  that 
  these 
  sandstones 
  and 
  shales 
  are 
  

   only 
  apparently 
  continuous 
  with 
  the 
  Frankfort 
  of 
  the 
  Mohawk, 
  the 
  

   Frankfort 
  pinching 
  out 
  gradually 
  eastward 
  and 
  the 
  Schenectady 
  

   beds 
  rapidly 
  thinning 
  out 
  westward. 
  The 
  Schenectady 
  formation 
  

   is 
  therefore 
  now 
  considered 
  as 
  of 
  middle 
  and 
  upper 
  Trenton 
  age. 
  

  

  The 
  life 
  of 
  this 
  formation 
  has 
  proved 
  to 
  be 
  an 
  extremely 
  pe- 
  

   culiar 
  one. 
  It 
  consists 
  of 
  a 
  few 
  graptolites, 
  brachiopods, 
  cephalo- 
  

   pods, 
  lamellibranchs, 
  trilobites 
  and 
  ostracods 
  of 
  upper 
  Trenton 
  

   aspect, 
  with 
  prenuncial 
  Utica 
  forms, 
  but 
  besides 
  there 
  occurs, 
  in 
  

   certain 
  layers, 
  a 
  profuse 
  mass 
  of 
  fragments 
  of 
  new 
  eurypterids 
  

   and 
  seaweeds 
  (Sphenophycus 
  latifolms). 
  Ten 
  species 
  of 
  euryp- 
  

   terids, 
  belonging 
  to 
  various 
  genera, 
  have 
  so 
  far 
  been 
  recognized, 
  

   but 
  it 
  is 
  obvious 
  from 
  fragments 
  of 
  sculptured 
  pieces 
  of 
  integument 
  

   that 
  the 
  fauna 
  was 
  still 
  greater. 
  The 
  seaweeds, 
  the 
  rapid 
  alterna- 
  

   tions 
  of 
  shales 
  and 
  sandstones 
  and 
  the 
  mud 
  cracks 
  indicate 
  that 
  the 
  

   great 
  thickness 
  of 
  beds 
  was 
  deposited 
  in 
  shallow 
  water, 
  and 
  the 
  

   uniformity 
  of 
  the 
  formation 
  shows 
  that 
  this 
  water 
  kept 
  deepening 
  

   approximately 
  proportional 
  to 
  the 
  accumulation 
  of 
  the 
  sediments. 
  

   The 
  formation 
  extends 
  mainly 
  from 
  southwest 
  to 
  northeast 
  in 
  a 
  

   trough 
  that 
  is 
  here 
  termed 
  the 
  lower 
  Mohawk 
  or 
  western 
  trough. 
  

  

  While 
  at 
  present 
  the 
  formation 
  reaches 
  only 
  the 
  southwestern 
  

   corner 
  of 
  the 
  Saratoga 
  quadrangle, 
  its 
  great 
  thickness 
  on 
  the 
  ad- 
  

   joining 
  Schenectady 
  quadrangle, 
  and 
  the 
  fact 
  that 
  the 
  strike 
  of 
  the 
  

   formation 
  is 
  in 
  the 
  direction 
  of 
  this 
  sheet, 
  leave 
  no 
  doubt 
  that 
  it 
  

   once 
  extended 
  much 
  farther 
  north, 
  probably 
  across 
  the 
  sheet, 
  and 
  

   has 
  since 
  been 
  eroded 
  away. 
  

  

  The 
  edge 
  of 
  the 
  formation 
  forms 
  now 
  a 
  low 
  escarpment, 
  shown 
  

   by 
  the 
  contour 
  lines 
  in 
  the 
  very 
  southwest 
  corner 
  of 
  the 
  sheet, 
  and 
  

   this, 
  like 
  the 
  typical 
  Helderberg 
  escarpment, 
  farther 
  south, 
  is 
  clear 
  

   evidence 
  of 
  the 
  former 
  extension 
  farther 
  northward 
  of 
  the 
  

   formation. 
  

  

  1 
  Op. 
  cit., 
  p. 
  50. 
  

  

  