﻿Palaeozoic 
  Bivalved 
  Entomostraca. 
  379 
  

  

  It 
  is 
  almost 
  the 
  same 
  as 
  fig. 
  1 
  of 
  PI. 
  XVI., 
  but 
  is 
  not 
  so 
  

   full 
  behind, 
  being 
  more 
  nearly 
  oblong, 
  and 
  it 
  has 
  the 
  front 
  

   edge 
  of 
  the 
  sulcus 
  more 
  decidedly 
  raised 
  or 
  thickened. 
  

  

  4. 
  Primitia 
  cequalis, 
  Jones 
  & 
  Holl, 
  young 
  form. 
  

   (PI. 
  XVII. 
  fig. 
  2.) 
  

  

  Fig. 
  2 
  (from 
  specimen 
  no. 
  30), 
  larger 
  and 
  of 
  a 
  fuller 
  shape 
  

   than 
  rig. 
  1, 
  appears 
  to 
  have 
  one 
  edge 
  of 
  the 
  sulcus 
  raised 
  and 
  

   isolated 
  as 
  a 
  pimple, 
  and 
  the 
  other 
  moiety 
  of 
  the 
  valve 
  is 
  

   slightly 
  rucked 
  up 
  ; 
  but, 
  seen 
  in 
  another 
  light, 
  each 
  side 
  of 
  the 
  

   sulcus 
  appears 
  to 
  end 
  dorsally 
  in 
  a 
  little 
  pimple, 
  so 
  that 
  in 
  

   this 
  view 
  there 
  are 
  two 
  little 
  nearly 
  equal 
  knobs 
  near 
  the 
  

   back 
  at 
  the 
  ends 
  of 
  the 
  curved 
  boundary 
  of 
  the 
  sulcus, 
  thus 
  

   feebly 
  imitating 
  P. 
  cequalis 
  (Ann. 
  & 
  Mag. 
  Nat. 
  Hist. 
  ser. 
  5, 
  

   vol. 
  xvii. 
  1886, 
  p. 
  411, 
  pi. 
  xiv. 
  fig. 
  11). 
  There 
  is 
  no 
  pub- 
  

   lished 
  figure 
  exactly 
  like 
  fig. 
  2, 
  though 
  P. 
  na?ia, 
  Jones 
  (op. 
  

   cit. 
  ser. 
  2, 
  vol. 
  xvi. 
  1855, 
  pi. 
  vi. 
  fig. 
  22), 
  in 
  some 
  degree, 
  and 
  

   more 
  especially 
  the 
  young 
  form 
  of 
  P. 
  cornuta, 
  J. 
  & 
  H. 
  (op. 
  

   cit. 
  May 
  1886, 
  pi. 
  xiv. 
  fig. 
  13), 
  have 
  somewhat 
  analogous 
  

   features. 
  Further, 
  as 
  the 
  young 
  of 
  P. 
  cornuta 
  is 
  to 
  the 
  

   adult, 
  so 
  probably 
  the 
  specimen 
  under 
  notice 
  is 
  to 
  the 
  adult 
  

   form 
  of 
  P. 
  cequalis 
  {ibid. 
  fig. 
  11), 
  the 
  pimple 
  and 
  ridge 
  being 
  

   near 
  the 
  dorsal 
  edge 
  and 
  each 
  other. 
  

  

  5. 
  Beyrichia 
  Kloedent, 
  M'Coy, 
  var. 
  acadica, 
  Jones. 
  

   (PI. 
  XVII. 
  figs. 
  3-6, 
  8, 
  9.) 
  

  

  As 
  explained 
  further 
  on, 
  these 
  seem 
  to 
  be 
  referable 
  to 
  a 
  

   variety 
  of 
  B. 
  Klcedeni, 
  having 
  a 
  considerable 
  variability 
  of 
  

   lobes 
  and 
  furrows, 
  as 
  is 
  the 
  case 
  with 
  the 
  true 
  B. 
  Kloedeni, 
  

   but 
  without 
  the 
  tuberculation 
  of 
  surface 
  which 
  is 
  present 
  in 
  

   the 
  analogous 
  varieties 
  (B. 
  clausa 
  &c), 
  and 
  with 
  a 
  strong 
  

   marginal 
  rim 
  in 
  well-preserved 
  individuals. 
  So 
  close 
  an 
  

   analogue 
  to 
  the 
  Carboniferous 
  B. 
  gigantea 
  is 
  seen 
  in 
  fig. 
  3 
  

   that, 
  keeping 
  B. 
  Kloedeni 
  as 
  the 
  type, 
  it 
  is 
  possible 
  that 
  we 
  

   shall 
  have 
  to 
  regard 
  B. 
  gigantea 
  not 
  as 
  a 
  real 
  species 
  *, 
  but 
  

   as 
  var. 
  gigantea 
  of 
  B. 
  Klcedeni. 
  

  

  Thus 
  also 
  another 
  Carboniferous 
  recurrent 
  form 
  and 
  of 
  

   specific 
  standing 
  is 
  seen 
  in 
  our 
  fig. 
  7 
  of 
  the 
  same 
  Plate 
  (see 
  

   p. 
  381). 
  

  

  Fig. 
  3 
  (from 
  no. 
  27) 
  has 
  a 
  decidedly 
  Beyrichian 
  aspect, 
  

   and 
  might 
  pass 
  for 
  a 
  variety 
  of 
  B. 
  Klaedeni, 
  such 
  as 
  the 
  

  

  * 
  Further 
  research, 
  however, 
  amonjr 
  the 
  numerous 
  specimens 
  from 
  

   Glencartholm, 
  Dumfriesshire, 
  is 
  indispensable 
  before 
  arriving- 
  at 
  this 
  con- 
  

   clusion. 
  

  

  