﻿CLASSIFICATION, 
  ETC. 
  OF 
  HAMILTON 
  AND 
  CHEMUNG 
  SERIES 
  319 
  

  

  typical 
  locality 
  occur 
  in 
  the 
  Corniferous 
  of 
  Ohio, 
  Hamilton 
  of 
  

   Milwaukee, 
  and 
  Upper 
  Devonian 
  of 
  Johnson 
  co., 
  Iowa. 
  

  

  Newberry® 
  describes 
  but 
  does 
  not 
  figure 
  a 
  small 
  dorso-median 
  

   plate 
  referred 
  to 
  D. 
  tuberculatus 
  of 
  which 
  the 
  anterior 
  half 
  only 
  

   was 
  preserved. 
  He 
  noticed 
  " 
  a 
  strong 
  keel 
  on 
  the 
  under 
  sur- 
  

   face," 
  but 
  though 
  warranted 
  in 
  assuming 
  that 
  the 
  latter 
  " 
  ter- 
  

   minated 
  behind 
  in 
  a 
  neck-like 
  process 
  projecting 
  downward," 
  it 
  

   is 
  apparent 
  from 
  his 
  own 
  statement 
  that 
  the 
  latter 
  was 
  not 
  

   observed. 
  Had 
  Newberry 
  possessed 
  other 
  and 
  more 
  perfect 
  ex- 
  

   amples 
  of 
  this 
  plate, 
  he 
  could 
  not 
  have 
  failed 
  to 
  notice 
  their 
  re- 
  

   semblance 
  to 
  his 
  D. 
  precursor, 
  from 
  the 
  Corniferous 
  of 
  Ohio. 
  A 
  

   comparison 
  of 
  the 
  type 
  of 
  the 
  latter 
  " 
  species 
  " 
  with 
  several 
  other 
  

   homologous 
  plates 
  from 
  the 
  Chemung 
  of 
  Warren, 
  Pennsylvania, 
  

   now 
  preserved 
  in 
  the 
  museums 
  of 
  Columbia 
  and 
  Yale 
  universi- 
  

   ties, 
  leads 
  the 
  writer 
  to 
  believe 
  thatD. 
  precursor 
  and 
  D. 
  tuber 
  culatus 
  

   are 
  identical, 
  in 
  which 
  case 
  the 
  latter 
  name 
  takes 
  precedence. 
  

  

  Lest 
  the 
  objection 
  be 
  raised 
  that 
  the 
  Chemung 
  plates 
  exhibit 
  a 
  

   somewhat 
  different 
  outline 
  anteriorly 
  from 
  Newberry's 
  figure 
  of 
  

   D. 
  precursor, 
  the 
  fact 
  must 
  not 
  be 
  overlooked 
  that 
  the 
  latter 
  is 
  

   not 
  strictly 
  accurate. 
  Newberry 
  6 
  states 
  that 
  a 
  the 
  keel 
  of 
  the 
  

   under 
  side 
  is 
  buried 
  in 
  the 
  rock, 
  and 
  its 
  form 
  can 
  not 
  be 
  made 
  

   out." 
  The 
  truth 
  is 
  that 
  the 
  keel, 
  which 
  lay 
  uppermost 
  and 
  was 
  

   exposed, 
  has 
  been 
  almost 
  entirely 
  broken 
  away; 
  and 
  the 
  dorsal 
  

   side 
  of 
  the 
  plate 
  is 
  embedded 
  in 
  the 
  rock, 
  or 
  where 
  abraded 
  or 
  

   corroded 
  away, 
  has 
  left 
  its 
  impression 
  in 
  the 
  rock. 
  A 
  restora- 
  

   tion 
  to 
  the 
  left 
  antelateral 
  margin 
  is 
  indicated 
  by 
  the 
  dotted 
  

   outline 
  in 
  plate 
  41, 
  but 
  the 
  figure 
  leads 
  one 
  to 
  suppose 
  that 
  the 
  

   corresponding 
  antelateral 
  margin 
  on 
  the 
  right-hand 
  side 
  of 
  

   the 
  specimen 
  was 
  entire, 
  which 
  is 
  not 
  the 
  case. 
  The 
  impression 
  

   in 
  the 
  rock 
  is 
  so 
  faint 
  and 
  confused 
  that 
  it 
  is 
  difficult 
  to 
  trace 
  the 
  

   outline 
  of 
  the 
  anterior 
  fourth 
  of 
  the 
  plate; 
  but 
  it 
  is 
  certain 
  that 
  

   the 
  antelateral 
  angle 
  was 
  acute 
  instead 
  of 
  being 
  rounded, 
  and 
  

   was 
  gently 
  curved 
  inward 
  instead 
  of 
  flaring 
  outward 
  as 
  shown. 
  

   The 
  chief 
  peculiarities 
  of 
  this 
  shield, 
  as 
  noted 
  by 
  Newberry, 
  are 
  

  

  a 
  Newberry, 
  J. 
  S. 
  The 
  palaeozoic 
  fishes 
  of 
  North 
  America 
  (Monogr. 
  U. 
  S. 
  geol. 
  surv. 
  1889, 
  16:98). 
  

   b 
  Ibid. 
  p. 
  51. 
  

  

  