﻿Report 
  of 
  the 
  State 
  Geologist. 
  351 
  

  

  the 
  forms 
  of 
  the 
  Hamilton 
  shales, 
  commingled 
  with 
  stragglers 
  

   from 
  the 
  Upper 
  Helderberg 
  fauna 
  beneath, 
  which, 
  however, 
  

   during 
  the 
  period 
  of 
  their 
  migrations 
  and 
  descent 
  have 
  not 
  

   escaped 
  modification. 
  Such 
  are 
  an 
  Orthis, 
  like 
  0. 
  lenticularis, 
  a 
  

   small 
  form 
  of 
  Godosjpira 
  Camilla 
  which 
  is 
  quite 
  abundant, 
  

   Ghonetes 
  like 
  G. 
  Yandellana 
  and 
  a 
  small 
  form 
  of 
  Orthothetes 
  

   Pandora. 
  The 
  stratum 
  has 
  also 
  furnished 
  two 
  new 
  species, 
  

   Orthoceras 
  incarceratum 
  and 
  Orthothetes 
  hellulus. 
  In 
  the 
  bed 
  of 
  

   impure 
  limestone 
  lying 
  immediately 
  beneath, 
  Ghonetes 
  lineata, 
  a 
  

   Corniferous 
  species, 
  has 
  also 
  been 
  observed 
  in 
  association 
  with 
  

   Liorhynchus 
  limitaris. 
  

  

  Above 
  852 
  feet 
  are 
  twenty-eight 
  feet 
  of 
  black 
  bituminous 
  shales, 
  

   quite 
  abundantly 
  f 
  ossilif 
  erous 
  at 
  top 
  and 
  bottom 
  with 
  the 
  charac- 
  

   teristic 
  species 
  of 
  this 
  group, 
  but 
  in 
  the 
  middle 
  barren 
  of 
  organic 
  

   remains. 
  Then 
  follows 
  a 
  two-foot 
  compact 
  chocolate 
  limestone 
  

   which 
  I 
  have 
  termed 
  the 
  Stafford 
  limestone 
  from 
  its 
  excellent 
  

   development 
  at 
  Stafford, 
  Genesee 
  county; 
  a 
  stratum 
  persistent 
  

   from 
  Livonia 
  eastward 
  to 
  an 
  unknown 
  distance, 
  probably 
  not 
  less 
  

   than 
  fifty 
  miles. 
  In 
  the 
  shaft 
  section, 
  as 
  at 
  all 
  its 
  observed 
  out- 
  

   crops, 
  it 
  bears 
  a 
  Hamilton 
  fauna 
  with 
  a 
  few 
  of 
  the 
  Marcellus 
  

   shale 
  species, 
  all 
  usually 
  in 
  a 
  fine 
  condition 
  of 
  preservation. 
  

   From 
  this 
  horizon 
  upward 
  there 
  are 
  no 
  more 
  limestones 
  in 
  the 
  

   Marcellus 
  section. 
  -Th& 
  shales 
  which 
  begin 
  at 
  822 
  feet 
  bear 
  almost 
  

   exclusively 
  species 
  characteristic 
  of 
  the 
  group, 
  but 
  in 
  the 
  course 
  

   of 
  fifty 
  feet 
  there 
  is 
  a 
  gradual 
  appearance 
  of 
  Hamilton 
  fossils, 
  

   which 
  have 
  before 
  been 
  met 
  with 
  only 
  in 
  the 
  limestone 
  layers 
  

   beneath. 
  This 
  presence 
  of 
  Hamilton 
  species 
  becomes 
  perceptible 
  

   at 
  once 
  above 
  794 
  feet 
  and 
  more 
  strongly 
  expressed 
  throughout 
  

   the 
  thick 
  bed 
  of 
  black, 
  bituminous 
  shale 
  extending 
  from 
  this 
  

   point 
  to 
  650 
  feet. 
  The 
  passage 
  of 
  these 
  black 
  shale 
  beds 
  of 
  the 
  

   Marcellus, 
  with 
  their 
  fauna, 
  into 
  the 
  Hamilton 
  division 
  with 
  its 
  

   fauna 
  is 
  imperceptible. 
  From 
  the 
  Stafford 
  limestone 
  at 
  823 
  feet 
  

   up 
  to 
  the 
  base 
  of 
  the 
  Encrinal 
  limestone 
  at 
  562 
  feet 
  there 
  is 
  a 
  

   gradual 
  lessening 
  of 
  bituminous 
  matter 
  in 
  the 
  shales, 
  a 
  progressive 
  

   increase 
  in 
  their 
  argillaceous 
  character, 
  and 
  likewise 
  a 
  gradual 
  dis- 
  

   appearance 
  of 
  the 
  Marcellus 
  species 
  and 
  a 
  progressive 
  increase 
  of 
  

   those 
  characteristic 
  of 
  the 
  shales 
  above. 
  We 
  may 
  approximately 
  

   and 
  quite 
  conventionally 
  place 
  the 
  upper 
  limit 
  of 
  the 
  Marcellus 
  

   at 
  about 
  650 
  feet, 
  but 
  above 
  this 
  horizon 
  both 
  the 
  organic 
  and 
  

  

  