﻿T. 
  DAVIDSON 
  AND 
  "W. 
  KING 
  ON 
  THE 
  TEIMEEELLID^. 
  

  

  169 
  

  

  DESCRIPTION 
  OP 
  PLATES. 
  

   Plate 
  XII. 
  

  

  Diagram 
  figures 
  of 
  the 
  cardinal 
  and 
  internal 
  parts 
  of 
  Trimerella 
  (figs. 
  1, 
  2, 
  

   7, 
  8), 
  Monomerella 
  (figs. 
  3, 
  4), 
  and 
  Dinobolus 
  (fig3. 
  5, 
  6). 
  

  

  Pedicle- 
  or 
  Ventral 
  Valve. 
  

  

  a. 
  Deltidiuin. 
  

  

  b. 
  Deltidial 
  slope. 
  

  

  c. 
  Deltidial 
  ridges. 
  

  

  d. 
  Area! 
  borders. 
  

  

  e. 
  Cardinal 
  callosities. 
  

  

  f. 
  Cardinal 
  facet. 
  

  

  g. 
  Lozenge. 
  

  

  h. 
  Cardinal 
  buttress. 
  

  

  i. 
  Urnbonal 
  chambers. 
  

  

  j. 
  Platform. 
  

  

  k. 
  Platform 
  vaults. 
  

  

  1. 
  Median 
  plate. 
  

  

  m. 
  Median 
  scars. 
  

  

  n. 
  Anterior 
  scars. 
  

  

  o. 
  Lateral 
  scars. 
  

  

  p. 
  Postmedian 
  scars. 
  

  

  q. 
  Crown 
  1 
  

  

  r. 
  Side 
  [■ 
  Crescent. 
  

  

  s. 
  End 
  J 
  

  

  t. 
  Transverse 
  scars. 
  

  

  u. 
  Archlet. 
  

  

  w. 
  Subcardinal 
  scars. 
  

   x. 
  Umbo-lateral 
  scars. 
  

  

  Brachial 
  or 
  Dorsal 
  Valve. 
  

  

  d. 
  

  

  e. 
  Cardinal 
  sockets. 
  

  

  /■ 
  

  

  9- 
  

  

  h. 
  

  

  i. 
  

  

  j. 
  Platform. 
  

  

  k. 
  Platform 
  vaults. 
  

  

  I. 
  Median 
  plate. 
  

  

  m. 
  Median 
  scars. 
  

  

  n. 
  Anterior 
  scars. 
  

  

  o. 
  Lateral 
  scars. 
  

  

  p. 
  Postmedian 
  scars. 
  

  

  q. 
  Crown 
  "1 
  

  

  r. 
  Side 
  I 
  Crescent. 
  

  

  s. 
  End 
  J 
  

  

  t. 
  Transverse 
  scars. 
  

  

  u. 
  Archlet. 
  

  

  v. 
  Cardinal 
  scars. 
  

  

  w. 
  Subcardinal 
  scars. 
  

  

  x. 
  Umbo-lateral 
  scars. 
  

  

  Fig. 
  1. 
  Pedicle-valve 
  of 
  the 
  genus 
  Trimerelld, 
  principally 
  from 
  specimens 
  of 
  T. 
  

   grandis. 
  k, 
  vaults 
  passing 
  under 
  the 
  platform, 
  j 
  ; 
  i, 
  chambers 
  in 
  the 
  

   umbo, 
  one 
  on 
  each 
  side 
  of 
  the 
  cardinal 
  buttress, 
  h. 
  The 
  urnbonal 
  

   chambers 
  and 
  their 
  casts 
  are 
  exhibited 
  in 
  fig. 
  2 
  c, 
  and 
  fig. 
  2, 
  PI. 
  XIII. 
  

  

  2. 
  Brachial 
  valve 
  of 
  the 
  same 
  genus, 
  principally 
  from 
  T. 
  grandis 
  and 
  

  

  T. 
  ohioensis. 
  The 
  scars, 
  s 
  (also 
  their 
  correspondencies, 
  s, 
  in 
  the 
  pe- 
  

   dicle-valve), 
  are 
  usually 
  difficult 
  to 
  define 
  ; 
  but 
  the 
  left-hand 
  one, 
  as 
  

   shown 
  in 
  a 
  woodcut 
  in 
  the 
  text 
  (p. 
  146), 
  has 
  been 
  satisfactorily 
  made 
  

   out 
  in 
  one 
  of 
  the 
  specimens 
  we 
  have 
  examined. 
  

  

  3. 
  Pedicle-valve 
  of 
  Monomerella, 
  chiefly 
  made 
  up 
  from 
  M. 
  prisca 
  and 
  M. 
  

  

  Walmstedti. 
  h, 
  a 
  perpendicular 
  plate 
  supporting 
  the 
  binge 
  (cardinal 
  

   buttress) 
  ; 
  it 
  is 
  thinner 
  than 
  usually 
  in 
  Trimerella 
  : 
  x, 
  umbo-lateral 
  

   scars 
  that 
  occur 
  one 
  on 
  the 
  outer 
  side 
  of 
  each 
  urnbonal 
  chamber, 
  i. 
  

  

  4. 
  Brachial 
  valve 
  of 
  the 
  same 
  genus. 
  The 
  scars, 
  x, 
  probably 
  occur 
  in 
  

  

  Trimerella, 
  fig. 
  2 
  ; 
  but 
  they 
  have 
  not 
  been 
  satisfactorily 
  detected 
  (ap- 
  

   parently 
  a 
  pair 
  of 
  corresponding 
  scars, 
  x, 
  occur 
  in 
  the 
  pedicle-valve 
  of 
  

   Trimerella, 
  fig. 
  1) 
  : 
  they 
  are 
  very 
  obvious, 
  however, 
  in 
  a 
  cast 
  of 
  Mo- 
  

   nomerella 
  prisca. 
  

  

  5. 
  Pedicle-valve 
  of 
  Dinobolus, 
  chiefly 
  from 
  specimens 
  of 
  D. 
  Davidsoni 
  and 
  

  

  D. 
  Conradi. 
  The 
  pair 
  of 
  subcardinal 
  scars, 
  w, 
  is 
  on 
  the 
  edge 
  (rounded) 
  

   of 
  the 
  binge. 
  The 
  pah", 
  x, 
  are 
  below 
  the 
  latter, 
  each 
  member 
  in 
  a 
  shal- 
  

   low 
  depression 
  corresponding 
  to 
  an 
  internal 
  chamber. 
  

  

  6. 
  Brachial 
  valve 
  of 
  the 
  same 
  genus, 
  p 
  has 
  much 
  the 
  appearance 
  of 
  a 
  

  

  visceral 
  scar. 
  The 
  parts, 
  r 
  and 
  s, 
  have 
  been 
  determined 
  from 
  a 
  num- 
  

   ber 
  of 
  good 
  examples 
  of 
  D. 
  Davidsoni. 
  Taking 
  in 
  the 
  line 
  that 
  runs 
  

   off 
  from 
  the 
  hinge 
  a 
  little 
  distance 
  along 
  and 
  within 
  the 
  postlateral 
  

   margins 
  of 
  the 
  valve 
  (the 
  line 
  was 
  detected 
  on 
  the 
  right 
  of 
  one 
  of 
  these 
  

  

  