﻿Palaeozoic 
  Bivalved 
  Entomostraca. 
  383 
  

  

  B. 
  Klcedeni, 
  M'Coy, 
  that 
  u 
  B. 
  Wilckensiana, 
  Jones, 
  [Prirnitia] 
  

   complicata, 
  Salter, 
  [P.] 
  strangulata, 
  Salter, 
  [P.] 
  obliquejugata, 
  

   Schmidt, 
  might 
  be 
  only 
  varieties 
  of 
  B. 
  Kloedeni 
  due 
  to 
  age 
  " 
  — 
  

   the 
  more 
  or 
  less 
  elongate, 
  simple, 
  or 
  divided 
  forms 
  of 
  the 
  

   main 
  lobes, 
  and 
  the 
  obliteration 
  of 
  the 
  central 
  boss, 
  leaving 
  

   only 
  two 
  ridges, 
  constituting 
  the 
  differences. 
  This 
  is 
  by 
  far 
  

   too 
  sweeping 
  a 
  conclusion, 
  ignoring 
  the 
  probable 
  physiolo- 
  

   gical 
  value 
  of 
  the 
  various 
  soft 
  parts 
  and 
  limbs 
  covered 
  by 
  

   or 
  occupying 
  different 
  parts 
  of 
  the 
  valves, 
  and 
  fitted 
  for 
  diffe- 
  

   rently 
  constructed 
  valves. 
  That 
  there 
  are 
  zoological 
  relation- 
  

   ships 
  among 
  the 
  Ostracoda, 
  as 
  among 
  both 
  lower 
  and 
  higher 
  

   animals, 
  no 
  one 
  can 
  doubt 
  ; 
  but 
  until 
  we 
  can 
  define 
  the 
  evi- 
  

   dence 
  thereof 
  as 
  clearly 
  as 
  M. 
  Verworn 
  has 
  defined 
  the 
  stages 
  

   of 
  his 
  Beyrichia 
  primitiva 
  the 
  present 
  arrangements 
  had 
  

   better 
  remain, 
  so 
  as 
  to 
  avoid 
  confusion. 
  

  

  7. 
  Isocltilina 
  labrosa, 
  sp. 
  no 
  v. 
  

   (PI. 
  XVII. 
  fig. 
  11, 
  and 
  woodcuts, 
  tigs. 
  3 
  and 
  4.) 
  

  

  Besides 
  true 
  Leperdilice 
  among 
  the 
  Palasozoic 
  Ostracoda 
  we 
  

   not 
  unfrequently 
  find 
  forms 
  that 
  approach 
  them 
  in 
  shape 
  and 
  

   sometimes 
  in 
  relative 
  size, 
  but 
  without 
  having 
  some 
  of 
  the 
  

   true 
  characteristics, 
  such 
  as 
  are 
  defined 
  in 
  the 
  Ann. 
  & 
  Mag. 
  

   Nat. 
  Hist. 
  November 
  1881, 
  pp. 
  334, 
  335. 
  It 
  is 
  to 
  be 
  noted, 
  

   however, 
  that 
  such 
  a 
  Leperditia 
  as 
  var. 
  nana 
  of 
  L. 
  canadensis 
  

   (\e\fabulttes), 
  op. 
  cit. 
  April 
  1858, 
  pi. 
  ix. 
  fig. 
  12, 
  is 
  destitute 
  

   of 
  external 
  structural 
  marks 
  ; 
  and 
  so 
  are 
  some 
  Carboniferous 
  

   Leperditue 
  {op. 
  cit. 
  May 
  1865, 
  pi. 
  xx. 
  and 
  October 
  1886, 
  

   pi. 
  vii.). 
  

  

  My 
  friend 
  Mr. 
  J. 
  W. 
  Kirkby 
  agrees 
  with 
  me 
  in 
  stating 
  

   that 
  we 
  have 
  not 
  seen 
  the 
  eye-spot 
  or 
  the 
  muscle-spot 
  in 
  

   Leperditia 
  Youngiana 
  , 
  compressa, 
  parattela, 
  obesa, 
  and 
  some 
  

   other 
  Carboniferous 
  species. 
  In 
  Leperditia 
  Okeni 
  and 
  scoto- 
  

   burdigalensis 
  these 
  features 
  are 
  rarely 
  visible. 
  We 
  find 
  also 
  

   that 
  the 
  ventral 
  overlap 
  is 
  not 
  great 
  in 
  Leperditia 
  Youngiana 
  

   and 
  Armstrongiana 
  and 
  is 
  often 
  weak 
  in 
  L. 
  scotoburdigalen- 
  

   sis. 
  Not 
  unfrequently 
  it 
  varies 
  in 
  development 
  in 
  individuals, 
  

   the 
  larger 
  and 
  more 
  swollen 
  forms 
  having 
  generally 
  most 
  

   overlap. 
  

  

  In 
  Leperditian 
  forms 
  where 
  the 
  eye-spot 
  or 
  muscle-spot 
  or 
  

   both 
  are 
  present, 
  but 
  no 
  ventral 
  overlap, 
  the 
  genus 
  Isochilina 
  

   is 
  recognized. 
  

  

  The 
  specimen 
  before 
  us 
  (Cap 
  Bon-Ami, 
  no. 
  3), 
  fig. 
  11, 
  is 
  

   less 
  exactly 
  Leperditioid 
  than 
  fig. 
  10 
  of 
  the 
  same 
  Plate, 
  being 
  

   nearly 
  oblong, 
  but 
  rounded 
  on 
  the 
  free 
  margins. 
  It 
  is 
  very 
  

   similar 
  in 
  outline 
  to 
  Leperditia 
  canadensis, 
  var. 
  labrosa, 
  J. 
  

  

  