﻿Palcaozoic 
  Bivalved 
  Entomostraca. 
  377 
  

  

  separate 
  name 
  of 
  any 
  kind. 
  There 
  is 
  also 
  a 
  faint 
  depres- 
  

   sion 
  behind 
  and 
  parallel 
  to 
  the 
  posterior 
  edge 
  of 
  the 
  sulcus 
  ; 
  

   and 
  this 
  may 
  faintly 
  foreshadow 
  the 
  second 
  (hinder) 
  furrow- 
  

   in 
  BeyricMa. 
  As 
  internal 
  casts 
  often 
  show 
  developments 
  

   of 
  local 
  features 
  different 
  in 
  degree 
  from 
  what 
  are 
  seen 
  on 
  

   the 
  outside 
  of 
  the 
  valves 
  *, 
  possibly 
  the 
  perfect 
  valve 
  of 
  

   fig. 
  7 
  a 
  would 
  not 
  differ 
  much 
  from 
  fig 
  6 
  a, 
  allowing 
  for 
  the 
  

   fact 
  of 
  their 
  being 
  valves 
  of 
  the 
  two 
  different 
  sides, 
  and 
  one 
  

   being 
  of 
  larger 
  growth 
  than 
  the 
  other. 
  

  

  Several 
  other 
  casts 
  of 
  ordinary 
  small 
  Primitice 
  of 
  the 
  mun- 
  

   dida 
  type, 
  together 
  with 
  small 
  gasteropods 
  and 
  plant-remains, 
  

   accompany 
  fig. 
  7. 
  

  

  Fig. 
  8 
  (specimen 
  no. 
  7) 
  is 
  a 
  cast 
  with 
  a 
  partial 
  film 
  of 
  

   shell 
  and 
  an 
  obscure 
  trace 
  of 
  reticulate 
  ornament. 
  In 
  shape 
  

   it 
  is 
  much 
  like 
  figs. 
  4 
  and 
  6, 
  but 
  the 
  sulcus 
  is 
  broad, 
  deep, 
  

   and 
  curved, 
  the 
  curvature 
  having 
  its 
  convexity 
  in 
  a 
  direction 
  

   opposite 
  to 
  that 
  in 
  fig. 
  3 
  — 
  that 
  is, 
  curving 
  downwards 
  and 
  

   forwards, 
  not 
  downwards 
  and 
  backwards. 
  Behind 
  the 
  sulcus 
  

   there 
  are 
  two 
  slight 
  depressions, 
  possibly 
  homologous 
  with 
  

   the 
  slight 
  valley 
  behind 
  the 
  posterior 
  edge 
  of 
  the 
  sulcus 
  in 
  

   fig. 
  7 
  a. 
  If 
  this 
  be 
  taken 
  for 
  granted, 
  we 
  are 
  still 
  within 
  the 
  

   real 
  range 
  of 
  P. 
  mundula, 
  however 
  much 
  the 
  sulcus 
  be 
  inten- 
  

   sified. 
  There 
  is 
  here 
  no 
  indication 
  of 
  the 
  antero- 
  dorsal 
  

   depression 
  visible 
  in 
  fig. 
  7 
  a. 
  

  

  Fig. 
  9 
  (in 
  specimen 
  no. 
  9, 
  with 
  fish-remains) 
  is 
  a 
  crushed 
  

   cast, 
  with 
  broken 
  valve. 
  Its 
  special 
  value 
  is 
  that 
  we 
  here 
  see 
  

   an 
  example 
  of 
  the 
  typical 
  P. 
  mundula, 
  like 
  fig. 
  29 
  a, 
  pi. 
  vi. 
  

   1855, 
  referred 
  to 
  above. 
  

  

  2. 
  Primitia 
  scajjhoides, 
  sp. 
  nov. 
  (PI. 
  XVI. 
  fig. 
  3.) 
  

  

  PI 
  XVI. 
  fig. 
  3, 
  show's 
  a 
  dark 
  valve, 
  straight 
  on 
  the 
  back, 
  

   obliquely 
  and 
  elliptically 
  curved 
  on 
  the 
  free 
  margins, 
  boldly 
  

   curved 
  behind, 
  contracted 
  in 
  front, 
  and 
  with 
  the 
  hinge-line 
  

   shorter 
  than 
  the 
  valve. 
  The 
  sulcus 
  is 
  median 
  and 
  strong 
  

   (being 
  broad 
  and 
  deep), 
  crescentic, 
  with 
  its 
  posterior 
  edge 
  raised 
  

   into 
  two 
  obscure 
  close-set 
  tubercles. 
  The 
  surface 
  bears 
  an 
  

   indistinct 
  punctation. 
  There 
  is 
  some 
  resemblance 
  between 
  

   this 
  form 
  and 
  P. 
  semtcordata, 
  Jones 
  (op. 
  cit. 
  1855, 
  p. 
  172, 
  

   pi. 
  vi. 
  fig. 
  21, 
  and 
  1865, 
  p. 
  417), 
  but 
  the 
  latter 
  is 
  shorter 
  and 
  

   has 
  the 
  front, 
  and 
  not 
  the 
  hinder, 
  edge 
  of 
  the 
  sulcus 
  raised 
  

   into 
  a 
  little 
  tubercle. 
  It 
  would 
  be 
  more 
  like 
  P. 
  Salteriana, 
  

   J. 
  {ibid. 
  p. 
  172, 
  pi. 
  vi. 
  fig. 
  20 
  f, 
  and 
  p. 
  417), 
  were 
  it 
  

  

  * 
  See, 
  for 
  instance, 
  Ann. 
  & 
  Mag. 
  Nat. 
  Hist. 
  March 
  1869, 
  pi. 
  xiv. 
  figs. 
  5 
  

   and 
  6 
  ; 
  and 
  Verworn, 
  Zeitschr. 
  d. 
  g. 
  Gesellsch. 
  1887, 
  pi. 
  iii. 
  tigs. 
  3 
  and 
  6. 
  

   t 
  There 
  is 
  too 
  much 
  margin 
  in 
  this 
  figure. 
  

  

  