﻿748 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum, 
  

  

  to 
  the 
  Hamilton 
  group. 
  The 
  predominant 
  traits 
  of 
  the 
  fauna 
  

   are 
  Hamilton 
  ; 
  its 
  extra-Hamilton 
  species 
  are 
  rare, 
  especially 
  in 
  

   the 
  lower 
  parts 
  of 
  the 
  series. 
  Where 
  the 
  Tully 
  limestone 
  and 
  

   Genesee 
  shales 
  are 
  present, 
  it 
  is 
  at 
  the 
  outset 
  simply 
  a 
  recurrent 
  

   Hamilton 
  fauna, 
  gradually 
  becoming 
  modified 
  by 
  the 
  disappear- 
  

   ance 
  of 
  some 
  of 
  the 
  more 
  pronounced 
  Hamilton 
  types, 
  especially 
  

   the 
  gastropods, 
  slight 
  modifications 
  in 
  others 
  that 
  remain 
  and 
  

   the 
  introduction 
  of 
  new 
  specific 
  types. 
  

  

  Where 
  the 
  capstones 
  (Tully 
  and 
  Genesee) 
  of 
  the 
  normal 
  Ham- 
  

   ilton 
  are 
  wanting, 
  as 
  in 
  and 
  eastward 
  of 
  the 
  Chenango 
  valley, 
  

   s 
  uch 
  a 
  recurrence 
  is 
  not 
  possible. 
  The 
  Hamilton 
  fauna 
  has 
  per- 
  

   petuated 
  itself 
  without 
  interruption, 
  and 
  it 
  is, 
  therefore, 
  in 
  one 
  

   sense 
  logically 
  and 
  correctly 
  a 
  Hamilton 
  fauna. 
  Should 
  it 
  prove 
  

   possible 
  to 
  establish 
  the 
  horizon 
  of 
  these 
  absent 
  formations 
  in 
  

   this 
  eastward 
  region 
  there 
  might 
  be 
  found 
  therein 
  a 
  basis 
  of 
  

   division 
  m 
  the 
  succession. 
  But 
  notwithstanding 
  the 
  continuity 
  

   with 
  modification 
  of 
  the 
  Hamilton 
  fauna 
  in 
  the 
  Chenango 
  valley 
  

   and 
  eastward 
  the 
  intervention 
  of 
  the 
  Tully 
  and 
  Genesee 
  formations 
  

   westward, 
  makes 
  the 
  division, 
  which 
  must 
  also 
  be 
  recognized 
  in 
  the 
  

   eastward 
  region 
  ; 
  probably 
  here 
  the 
  best 
  index 
  of 
  the 
  change 
  will 
  

   prove 
  to 
  be 
  the 
  appearance 
  of 
  /Spirifer 
  mesastrialis, 
  which, 
  as 
  

   already 
  observed, 
  Frosser 
  has 
  recorded 
  from 
  a 
  locality 
  at 
  North 
  

   Norwich 
  several 
  miles 
  above 
  my 
  northernmost 
  record 
  in 
  the 
  

   Chenango 
  valley. 
  

  

  These 
  Ithaca 
  beds, 
  then, 
  occupy 
  the 
  place 
  of 
  the 
  Por'age 
  

   group, 
  as 
  the 
  immediate 
  successors 
  of 
  the 
  normal 
  Hamilton 
  

   series 
  of 
  central 
  and 
  western 
  New 
  York. 
  In 
  the 
  same 
  sense 
  the 
  

   mesastrialis-fsLUTtis^ 
  and 
  the 
  peculiar 
  Goniatite 
  fauna 
  of 
  the 
  typical 
  

   Portage 
  are 
  syntactic 
  in 
  the 
  time-scale 
  ; 
  but 
  to 
  speak 
  of 
  either 
  

   these 
  Ithaca 
  beds 
  or 
  the 
  mesastrialis 
  fauna 
  as 
  " 
  Portage 
  " 
  or 
  

   " 
  belonging 
  to 
  the 
  Portage 
  stage," 
  * 
  seems 
  to 
  me 
  misleading, 
  

   if 
  admissible. 
  

  

  There 
  are 
  certain 
  lithological 
  differences 
  in 
  the 
  Ithaca 
  beds 
  of 
  

   Cortland, 
  Chenango 
  and 
  Otsego 
  counties 
  and 
  the 
  typical 
  

   Portage 
  beds 
  of 
  Genesee, 
  Livingston 
  and 
  Ontario 
  counties. 
  

   Between 
  the 
  Portage 
  fauna 
  and 
  the 
  Ithaca 
  fauna 
  there 
  is 
  noth- 
  

   ing 
  in 
  common. 
  Two 
  syntactic 
  faunas 
  could 
  hardly 
  be 
  more 
  

   fundamentally 
  different. 
  We 
  speak 
  now 
  of 
  the 
  typical 
  Portage 
  

   fauna 
  ; 
  not 
  that 
  of 
  Ithaca, 
  but 
  that 
  of 
  the 
  Genesee 
  section 
  or 
  its 
  

  

  * 
  See 
  Prosser 
  op. 
  cit. 
  p. 
  230. 
  

  

  