﻿T. 
  DAVIDSON 
  AND 
  W. 
  KING 
  ON 
  THE 
  TRIMERELLID^. 
  137 
  

  

  impressions 
  referable 
  to 
  these 
  organs 
  have 
  occurred 
  to 
  us 
  : 
  they 
  

   have 
  been 
  found, 
  in 
  other 
  fossils*. 
  Such 
  impressions, 
  however, 
  

   may 
  yet 
  be 
  detected, 
  especially 
  of 
  the 
  apical 
  portion 
  in 
  the 
  pedicle- 
  

   valve. 
  

  

  In 
  some 
  specimens 
  a 
  shallow 
  submarginal 
  groove 
  is 
  present, 
  which 
  

   is 
  all 
  we 
  have 
  seen 
  that 
  could 
  be 
  attributed 
  to 
  the 
  setal 
  band. 
  It 
  is 
  

   extremely 
  doubtful, 
  from 
  the 
  construction 
  of 
  the 
  hinge, 
  that 
  this 
  

   organ 
  would 
  be 
  carried 
  round 
  the 
  posterior 
  margin 
  of 
  the 
  valves, 
  as 
  

   in 
  Lingula. 
  

  

  IV, 
  Affinities 
  op 
  the 
  Family. 
  

  

  Dall 
  places 
  the 
  genus 
  Trimerella 
  in 
  the 
  family 
  LinguUdce 
  ; 
  of 
  

   which 
  he 
  makes 
  two 
  divisions 
  (Lingulince 
  and 
  Obolince), 
  remarking 
  

   that 
  its 
  nearest 
  affinities 
  are 
  with 
  Lingula 
  and 
  Obolus, 
  but 
  adding 
  

   " 
  perhaps 
  it 
  may 
  be 
  eventually 
  placed 
  in 
  the 
  second 
  division 
  of 
  the 
  

   family 
  "f. 
  Hall, 
  referring 
  to 
  his 
  Dinobolus 
  Oonradi, 
  prefers 
  the 
  

   same 
  allocation, 
  asserting 
  that 
  it 
  is 
  closely 
  allied 
  to 
  Obolus 
  $. 
  The 
  

   same 
  may 
  be 
  said 
  of 
  Billings, 
  who 
  states 
  that 
  " 
  both 
  Trimerella 
  and 
  

   ■Monomerella 
  are 
  subgenera 
  [evidently 
  a 
  mistake 
  for 
  subgroups] 
  of 
  

   Obolus 
  : 
  " 
  he 
  also 
  adds 
  that 
  his 
  0. 
  canadensis 
  and 
  0. 
  galtensis 
  belong 
  

   to 
  "a 
  third 
  group 
  "§. 
  

  

  Quenstedt, 
  the 
  only 
  continental 
  palaeontologist 
  who 
  has 
  touched 
  

   on 
  the 
  subject 
  of 
  its 
  affinities, 
  includes 
  Trimerella 
  in 
  his 
  family 
  

   Ungulitoz 
  ; 
  which 
  he 
  makes 
  to 
  consist 
  of 
  Obolus, 
  Schmidtia, 
  Obolella, 
  

   and 
  Acrites 
  ||. 
  

  

  One 
  of 
  the 
  points 
  that 
  has 
  led 
  these 
  authors 
  to 
  affine 
  Trimerella 
  

   with 
  Obolus 
  is 
  possibly 
  the 
  resemblance 
  there 
  is 
  between 
  the 
  cres- 
  

   cent 
  of 
  the 
  former 
  and 
  certain 
  scars 
  which 
  curve 
  forward 
  from 
  the 
  

   hinge 
  of 
  the 
  latter. 
  Until 
  one 
  of 
  us 
  had 
  ascertained 
  that 
  the 
  scars 
  

   alluded 
  to 
  in 
  Obolus 
  represent 
  the 
  posterior 
  adductor 
  muscles 
  of 
  

   Discina*^, 
  and 
  not 
  other 
  organs, 
  as 
  in 
  Lingula, 
  we 
  were 
  also 
  inclined 
  

   to 
  take 
  the 
  view 
  of 
  our 
  colleagues 
  : 
  now, 
  however, 
  as 
  will 
  be 
  under- 
  

   stood 
  from 
  what 
  is 
  stated 
  in 
  the 
  previous 
  sections, 
  we 
  have 
  aban- 
  

   doned 
  it**. 
  

  

  Believing 
  that 
  the 
  Trimerellids 
  are 
  closely 
  related 
  to 
  the 
  Lingulids, 
  

   but 
  distinct 
  as 
  a 
  family, 
  we 
  shall 
  next 
  enter 
  upon 
  a 
  comparison 
  

   between 
  the 
  two 
  groups 
  by 
  tabulating 
  their 
  differences 
  and 
  agree- 
  

   ments 
  : 
  — 
  

  

  * 
  Such 
  as 
  Productus, 
  Ckonetes, 
  Strophalosia, 
  Strophomena, 
  KonincMna, 
  Ano- 
  

   htheca, 
  Bavidsonia, 
  &c. 
  

  

  t 
  American 
  Journal 
  of 
  Conchology, 
  vol. 
  vi. 
  part 
  2, 
  p. 
  153, 
  1870. 
  

  

  \ 
  Twentieth 
  Annual 
  Report 
  of 
  the 
  Regents 
  of 
  the 
  University 
  of 
  the 
  State 
  of 
  

   New 
  York, 
  1868 
  ; 
  and 
  revised 
  edition, 
  p. 
  376, 
  1870. 
  

  

  § 
  Canadian 
  Naturalist, 
  vol. 
  vi. 
  no. 
  2, 
  p. 
  222. 
  

  

  ]| 
  Petrefactenkunde 
  Deutschlands 
  ; 
  Die 
  Brachiopoden, 
  p. 
  668, 
  1871. 
  

  

  *|f 
  Ann. 
  Nat. 
  Hist. 
  ser. 
  4, 
  vol. 
  xii. 
  p. 
  13. 
  

  

  ** 
  It 
  may 
  be 
  mentioned 
  tbat 
  an 
  examination 
  of 
  a 
  large 
  number 
  of 
  specimens 
  

   belonging 
  to 
  the 
  genera 
  Obolus, 
  Schmidtia, 
  Obolella, 
  Acrites, 
  &c. 
  have 
  led 
  us 
  

   to 
  group 
  them 
  all 
  together 
  under 
  the 
  family 
  Obolida, 
  proposed 
  by 
  one 
  of 
  the 
  

   writers 
  in 
  1850 
  : 
  See 
  Monograph 
  of 
  Permian 
  Fossils, 
  p. 
  81. 
  

  

  