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  Twenty-eighth 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  plications 
  like 
  the 
  English 
  and 
  continental 
  European 
  speci- 
  

   mens. 
  The 
  Waldron 
  specimens 
  have 
  usually 
  the 
  form 
  of 
  

   those 
  illustrated 
  by 
  Mr. 
  Davidson* 
  as 
  8. 
  plicatella 
  var. 
  glo- 
  

   bosa. 
  This 
  author 
  says, 
  in 
  regard 
  to 
  the 
  surface 
  of 
  the 
  8. 
  

   plicatella 
  var. 
  radiata, 
  that 
  "the 
  external 
  sculpture, 
  when 
  

   4 
  ' 
  well 
  preserved, 
  is 
  extremely 
  beautiful, 
  and 
  consists 
  of 
  radiat- 
  

   " 
  ing 
  ribs 
  (five 
  in 
  the 
  width 
  of 
  a 
  line 
  in 
  the 
  middle 
  of 
  an 
  

   4 
  'average 
  sized 
  specimen), 
  not 
  always 
  quite 
  regular 
  in 
  their 
  

   " 
  respective 
  widths, 
  but 
  usually 
  leaving 
  an 
  interspace 
  between 
  

   " 
  each 
  two 
  of 
  about 
  the 
  width 
  of 
  one 
  of 
  the 
  ribs, 
  and 
  at 
  times 
  

   " 
  toward 
  the 
  margin, 
  there 
  are 
  smaller 
  ribs 
  interpolated; 
  these 
  

   ' 
  'ribs 
  are 
  regularly 
  crossed 
  by 
  equidistant, 
  concentric, 
  pro 
  

   "jecting 
  ridges, 
  which 
  give 
  to 
  the 
  shell 
  surface 
  a 
  beautifully 
  

   " 
  imbricated 
  appearance." 
  This 
  description 
  of 
  the 
  character 
  

   of 
  surface 
  of 
  the 
  English 
  specimens 
  is 
  scarcely 
  applicable 
  to 
  

   the 
  American 
  specimens 
  which 
  we 
  refer 
  to 
  8. 
  radiata. 
  In 
  

   the 
  Waldron 
  specimens, 
  the 
  radii 
  are 
  finer 
  than 
  above 
  de- 
  

   scribed, 
  there 
  being 
  eight 
  or 
  more 
  in 
  the 
  width 
  of 
  a 
  line, 
  

   while 
  the 
  interspaces 
  are 
  not 
  more 
  than 
  half 
  as 
  wide 
  as 
  the 
  

   radii. 
  The 
  radii 
  are 
  also 
  distinctly 
  flattened 
  and 
  are 
  in- 
  

   creased 
  by 
  bifurcation 
  or 
  dichotomizing, 
  and 
  rarely 
  by 
  inter- 
  

   calation 
  of 
  smaller 
  striae. 
  These 
  characters 
  are 
  illustrated 
  in 
  

   figure 
  30 
  of 
  plate 
  24. 
  The 
  concentric 
  striae 
  are 
  obscurely 
  

   visible 
  or 
  obsolete. 
  Of 
  the 
  Spirifera 
  plicatella 
  var. 
  globosa, 
  

   Mr. 
  Davidson 
  says: 
  "It 
  is 
  easily 
  connected 
  with 
  Spirifera 
  

   radiata 
  of 
  Sowerby. 
  Indeed, 
  there 
  appears 
  to 
  be 
  little 
  by 
  

   which 
  it 
  can 
  be 
  distinguished 
  from 
  the 
  true 
  Spirifera 
  radiata, 
  

   except 
  the 
  greater 
  convexity 
  or 
  gibbosity 
  of 
  its 
  valves 
  and 
  its 
  

   finer 
  striation." 
  

  

  The 
  Spirifera 
  Niagarensis, 
  which 
  has 
  a 
  similar 
  form 
  and 
  

   surface 
  markings 
  is 
  distinctly 
  plicate, 
  but 
  it 
  is 
  not 
  known 
  to- 
  

   present 
  the 
  elevated 
  area, 
  incurved 
  beak, 
  and 
  gibbous 
  form, 
  

   which 
  is 
  represented 
  in 
  the 
  European 
  specimens 
  of 
  8. 
  plica- 
  

   tella. 
  In 
  the 
  Niagara 
  shales 
  in 
  the 
  State 
  of 
  New 
  York 
  the 
  8. 
  

   JViagarensis 
  is 
  abundant, 
  while 
  8. 
  radiata 
  is 
  comparatively 
  

   rare. 
  At 
  Waldron 
  8. 
  radiata 
  has 
  acquired 
  a 
  remarkable 
  de- 
  

   velopment 
  in 
  numbers 
  and 
  in 
  the 
  size 
  of 
  the 
  specimens, 
  but 
  

   we 
  have 
  not 
  observed 
  a 
  single 
  specimen 
  of 
  8. 
  JViagarensis 
  in 
  

   all 
  the 
  collections 
  made 
  at 
  that 
  locality. 
  

  

  * 
  Monograph 
  of 
  British 
  Fossil 
  Brachiopoda, 
  p. 
  89, 
  pi. 
  9, 
  figs 
  7 
  and 
  8. 
  

  

  