﻿200 
  

  

  MISS 
  G. 
  L. 
  ELLES 
  ON 
  THE 
  SUBGENERA 
  [May 
  1897, 
  

  

  On 
  the 
  obverse 
  side 
  the 
  sicula 
  appears 
  to 
  be 
  free 
  for 
  ^ 
  of 
  its 
  

   length 
  on 
  the 
  right 
  side, 
  and 
  the 
  same 
  amount 
  is 
  seen 
  on 
  the 
  reverse 
  

   side. 
  

  

  Character 
  of 
  the 
  Mature 
  Rhabdosoma. 
  — 
  The 
  species 
  varies 
  some- 
  

   what 
  in 
  shape 
  ; 
  it 
  is 
  typically 
  as 
  broad 
  as 
  it 
  is 
  long, 
  but 
  in 
  some 
  

   specimens 
  it 
  is 
  rather 
  longer, 
  and 
  the 
  shape 
  then 
  is 
  a 
  broad 
  oval. 
  I 
  

   have 
  never 
  seen 
  a 
  specimen 
  that 
  exceeded 
  J 
  inch 
  in 
  length. 
  The 
  

   width 
  varies 
  in 
  different 
  specimens 
  from 
  § 
  to 
  | 
  inch. 
  

  

  Near 
  the 
  proximal 
  end 
  the 
  thecse 
  are 
  alternate 
  ; 
  where 
  the 
  thecae 
  

   become 
  horizontal 
  they 
  are 
  almost 
  opposite, 
  but 
  the 
  alternation 
  is 
  

   again 
  visible 
  at 
  the 
  distal 
  end. 
  The 
  thecse 
  are 
  -^ 
  inch 
  long 
  except 
  

   at 
  the 
  distal 
  extremity, 
  and 
  in 
  typical 
  forms 
  are 
  four 
  times 
  as 
  long 
  

   as 
  they 
  are 
  broad 
  ; 
  in 
  the 
  more 
  oval 
  forms 
  the 
  dimensions 
  are 
  

   slightly 
  less. 
  The 
  thecse 
  are 
  widest 
  at 
  their 
  apertures, 
  and 
  overlap 
  

   somewhat. 
  The 
  apertures 
  are 
  concave, 
  and 
  near 
  the 
  proximal 
  

   end 
  they 
  are 
  directed 
  downward, 
  but 
  towards 
  the 
  distal 
  end 
  this 
  is 
  

   not 
  so 
  marked. 
  There 
  are 
  about 
  42 
  apertures 
  in 
  the 
  space 
  of 
  1 
  inch. 
  

   The 
  angle 
  of 
  inclination 
  of 
  the 
  thecse 
  varies 
  greatly 
  at 
  different 
  

   points 
  along 
  the 
  length 
  of 
  the 
  rhabdosoma. 
  It 
  changes 
  as 
  follows 
  : 
  — 
  

   70°-90 
  o 
  -55 
  o 
  -45°. 
  The 
  thecse 
  are 
  all 
  concavely 
  curved, 
  but 
  the 
  

   curvature 
  is 
  greatest 
  near 
  the 
  proximal 
  end. 
  The 
  virgula 
  is 
  pro- 
  

   longed 
  beyond 
  the 
  distal 
  extremity. 
  

  

  When 
  the 
  form 
  is 
  longer 
  in 
  proportion 
  to 
  its 
  width, 
  this 
  seems 
  to 
  

   be 
  due 
  to 
  the 
  fact 
  that 
  there 
  is 
  a 
  difference 
  in 
  direction 
  of 
  growth 
  

   of 
  the 
  thecse 
  ; 
  fewer 
  thecse 
  are 
  curved 
  downward, 
  so 
  the 
  upward 
  

   inclination 
  begins 
  earlier. 
  

  

  General 
  Characters. 
  — 
  This 
  species 
  differs 
  from 
  all 
  others 
  

  

  (1) 
  In 
  the 
  various 
  angles 
  at 
  which 
  the 
  thecse 
  are 
  inclined 
  in 
  

  

  different 
  parts 
  of 
  the 
  rhabdosoma 
  ; 
  

  

  (2) 
  In 
  the 
  number 
  of 
  thecse 
  ; 
  

  

  (3) 
  In 
  having 
  the 
  apertures 
  of 
  the 
  thecse 
  recurved 
  towards 
  the 
  

  

  base. 
  

  

  Horizon. 
  — 
  This 
  species 
  occurs 
  in 
  Bohemia 
  in 
  shales 
  with 
  M. 
  tur- 
  

   riculatus 
  (Barr.), 
  and 
  M. 
  exiguus 
  (Nich.). 
  These 
  beds 
  are 
  probably 
  

   the 
  equivalents 
  of 
  our 
  Lower 
  Gala-Tarannon 
  beds. 
  

  

  British 
  Locality. 
  — 
  (?) 
  Conway, 
  North 
  Wales. 
  

  

  Table 
  of 
  Measurements. 
  

  

  No. 
  

  

  LD 
  *4*u°lL 
  

  

  Width. 
  

   opp.l 
  1 
  . 
  

  

  Max. 
  

  

  width. 
  

  

  Thecal 
  

   length. 
  

  

  No. 
  of 
  

   thecse. 
  

  

  Locality. 
  

  

  a 
  ... 
  

  

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  i. 
  

  

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  + 
  ft 
  

  

  22 
  

  

  Zelkovice, 
  Bohemia. 
  

  

  b... 
  

  

  1 
  

  

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  i 
  

  

  I 
  

  

  T* 
  

  

  24 
  

  

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  ,, 
  

  

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  ... 
  

  

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