﻿326 
  

  

  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  figure, 
  while 
  the 
  central 
  area 
  has 
  been 
  entirely 
  denuded. 
  This 
  

   gives 
  rise 
  to 
  the 
  appearance 
  of 
  a 
  raised 
  border 
  along 
  the 
  ante- 
  

   lateral 
  edges, 
  sometimes 
  ornamented 
  but 
  in 
  other 
  cases 
  smooth, 
  

   as 
  shown 
  in 
  plate 
  20 
  fig. 
  5 
  and 
  6 
  of 
  Newberry's 
  monograph. 
  

   Similar 
  raised 
  borders 
  have 
  been 
  observed 
  in 
  other 
  plates 
  besides* 
  

   the 
  antedorso-niedian, 
  thus 
  indicating 
  that 
  all 
  are 
  the 
  product 
  of 
  

   the 
  same 
  cause, 
  and 
  are 
  correlated 
  with 
  the 
  condition 
  of 
  overlap. 
  

  

  The 
  collection 
  also 
  contains 
  two 
  pectoral 
  appendages 
  belonging 
  

   to 
  the 
  left 
  side 
  of 
  the 
  body, 
  one 
  of 
  them 
  being 
  preserved 
  in 
  coun- 
  

   terpart. 
  They 
  are 
  about 
  the 
  average 
  size 
  of 
  those 
  in 
  B. 
  leidyi. 
  

   Some 
  of 
  the 
  ventral 
  plates 
  likewise 
  indicate 
  less 
  disparity 
  in 
  size 
  

   of 
  the 
  two 
  species 
  than 
  has 
  commonly 
  been 
  supposed. 
  No 
  exam- 
  

   ples 
  of 
  the 
  head 
  portion 
  are 
  represented 
  in 
  the 
  collection. 
  

  

  Locality; 
  same 
  as 
  preceding. 
  

  

  Family 
  Coccosteidae 
  

  

  Genus 
  dinichthys 
  

   Dinichthys 
  sp. 
  

   The 
  dinichthyid 
  plate 
  of 
  which 
  the 
  visceral 
  aspect 
  is 
  shown 
  

   in 
  the 
  annexed 
  figure 
  is 
  identifiable 
  as 
  the 
  left 
  anteventro- 
  

   lateral. 
  It 
  is 
  nearly 
  entire, 
  lacking 
  only 
  

   a 
  small 
  piece 
  from 
  each 
  of 
  the 
  antelateral 
  

   angles. 
  In 
  length 
  it 
  measures 
  4.4 
  cm, 
  and 
  

   in 
  maximum 
  breadth 
  2.8 
  cm. 
  It 
  is 
  quite 
  

   thin, 
  and 
  this 
  circumstance 
  taken 
  together 
  

   with 
  its 
  outline 
  and 
  rugose 
  markings 
  on 
  

   the 
  posterior 
  and 
  inner 
  margins, 
  due 
  prob- 
  

   ably 
  to 
  overlap, 
  compel 
  us 
  to 
  refer 
  to 
  it 
  to 
  

   the 
  ventral 
  surface 
  of 
  the 
  body. 
  There 
  is 
  

   an 
  obvious 
  similarity 
  in 
  outline 
  to 
  the 
  cor- 
  

   responding 
  plate 
  in 
  D. 
  minor, 
  and 
  a 
  lesser 
  

   resemblance 
  to 
  the 
  same 
  element 
  in 
  Coccos- 
  

   teus. 
  As 
  the 
  external 
  surface 
  is 
  firmly 
  em- 
  

   bedded 
  in 
  the 
  matrix, 
  it 
  is 
  impossible 
  to 
  observe 
  the 
  nature 
  of 
  

   the 
  ornamentation, 
  and 
  hence 
  a 
  specific 
  determination 
  is 
  quite 
  

  

  Fig. 
  6. 
  Dinichthys 
  sp. 
  Visceral 
  

   surface 
  of 
  right 
  anteventro- 
  

   lateral 
  plate. 
  

  

  a 
  Cf. 
  Newberry, 
  J. 
  S., 
  loc. 
  cit. 
  (1889). 
  pi. 
  47, 
  fig. 
  2. 
  

  

  