﻿194 
  Twenty-eighth 
  Beport 
  on 
  the 
  State 
  Museum. 
  

  

  the 
  middle 
  ranges 
  having 
  nine 
  each. 
  Palpebral 
  lobe 
  depressed, 
  

   giving 
  great 
  prominence 
  to 
  the 
  rim 
  of 
  the 
  eye. 
  Cheeks 
  small, 
  

   prominent 
  on 
  the 
  anterior 
  portion, 
  marked 
  near 
  the 
  posterior 
  

   border 
  by 
  a 
  deep 
  groove 
  — 
  the 
  continuation 
  of 
  the 
  occipital 
  

   furrow 
  ; 
  margin 
  broad 
  and 
  flat. 
  

  

  Thorax 
  with 
  the 
  axial 
  lobe 
  depressed-convex, 
  widest 
  at 
  the 
  

   sixth 
  segment, 
  its 
  greatest 
  width 
  more 
  than 
  two-thirds 
  that 
  of 
  

   the 
  lateral 
  lobe. 
  The 
  articulations 
  curve 
  forward 
  in 
  the 
  mid- 
  

   dle 
  and 
  at 
  their 
  junction 
  with 
  the 
  lateral 
  lobes, 
  near 
  the 
  ex- 
  

   tremities 
  they 
  are 
  bent 
  suddenly 
  backward, 
  terminating 
  in 
  a 
  

   sharp 
  point. 
  Articulations 
  of 
  the 
  lateral 
  lobes 
  traversed 
  by 
  

   a 
  deep 
  longitudinal 
  furrow 
  extending 
  from 
  the 
  middle 
  lobe 
  to 
  

   the 
  abrupt 
  curve 
  near 
  their 
  extremities. 
  

  

  Pygidium 
  somewhat 
  elongate-triangular, 
  extended 
  posteri- 
  

   orly 
  into 
  an 
  acute 
  spine 
  ; 
  central 
  lobe 
  or 
  axis 
  marked 
  by 
  ten 
  or 
  

   twelve 
  narrow 
  annulations 
  ; 
  the 
  lateral 
  lobes 
  less 
  prominently 
  

   marked 
  by 
  ten 
  flattened 
  ribs, 
  which 
  are 
  traversed 
  by 
  a 
  deep 
  

   furrow, 
  and 
  terminate 
  in 
  a 
  narrow 
  border 
  ; 
  the 
  two 
  posterior 
  

   pairs 
  of 
  ribs 
  are 
  directed 
  obliquely 
  backward. 
  

  

  Surface 
  of 
  the 
  head, 
  except 
  the 
  anterior 
  and 
  lateral 
  border, 
  

   covered 
  with 
  small 
  irregular 
  pustules, 
  the 
  border 
  being 
  finely 
  

   granulose. 
  The 
  remainder 
  of 
  the 
  body 
  is 
  granulose, 
  with 
  

   occasionally 
  small 
  pustules 
  on 
  the 
  axial 
  lobe 
  of 
  the 
  thorax. 
  

  

  The 
  Waldron 
  specimens 
  of 
  this 
  species 
  were 
  identified 
  with 
  

   specimens 
  from 
  Wisconsin, 
  which 
  formed 
  the 
  basis 
  of 
  the 
  

   original 
  description. 
  The 
  only 
  important 
  differences 
  noticed, 
  

   are 
  the 
  lesser 
  prolongation 
  of 
  the 
  anterior 
  process 
  ; 
  the 
  head 
  

   is 
  not 
  so 
  regularly 
  semi- 
  elliptical, 
  but 
  is 
  more 
  angular 
  on 
  the 
  

   posterior 
  side 
  ; 
  the 
  pygidium 
  is 
  somewhat 
  more 
  elongate 
  and 
  

   more 
  acutely 
  terminated. 
  The 
  species 
  was 
  originally 
  de- 
  

   scribed 
  from 
  specimens 
  of 
  the 
  buckler 
  and 
  pygidia. 
  In 
  the 
  

   recent 
  collections 
  from 
  Waldron, 
  there 
  are 
  several 
  specimens 
  

   retaining 
  the 
  thorax 
  nearly 
  entire, 
  and 
  from 
  these 
  the 
  descrip- 
  

   tion 
  of 
  the 
  species 
  has 
  been 
  completed. 
  

  

  Compared 
  with 
  D. 
  verrucosus, 
  the 
  head 
  is 
  proportionally 
  

   narrower, 
  the 
  postero-lateral 
  spines 
  longer 
  and 
  less 
  diverging 
  ; 
  

   the 
  pygidium 
  is 
  narrower 
  and 
  more 
  elongate, 
  and 
  the 
  surface 
  

   is 
  not 
  so 
  strongly 
  covered 
  with 
  pustules. 
  It 
  somewhat 
  resem- 
  

   bles 
  D. 
  limulurus 
  of 
  the 
  Niagara 
  formation 
  of 
  New 
  York, 
  

   but 
  differs 
  in 
  the 
  proportionally 
  larger 
  glabella, 
  the 
  larger 
  and 
  

   more 
  prominent 
  eyes, 
  and 
  the 
  extension 
  of 
  the 
  anterior 
  bor- 
  

   der. 
  

  

  Specimens 
  of 
  this 
  form 
  have 
  proved 
  comparatively 
  rare 
  in 
  

   the 
  collections 
  thus 
  far 
  made 
  at 
  Waldron. 
  

  

  