﻿'J. 
  DAVIDSON 
  AND 
  W. 
  KING 
  ON 
  TIIE 
  TRIHERELLIDJE. 
  167 
  

  

  valve*), 
  we 
  prefer 
  the 
  idea 
  that 
  they 
  represent 
  certain 
  viscera; 
  and 
  

   they 
  may 
  be 
  recesses 
  produced 
  by 
  the 
  pressure 
  of 
  ovarian 
  lobes 
  against 
  

   the 
  inner 
  side 
  of 
  the 
  postlateral 
  walls 
  of 
  the 
  splanchnoccele. 
  

  

  The 
  vascular 
  iuqjressions 
  in 
  the 
  anterior 
  half 
  of 
  the 
  fossil 
  are, 
  in 
  

   their 
  arrangement, 
  unlike 
  any 
  thing 
  we 
  have 
  seen 
  in 
  the 
  Trimerellids, 
  

   or 
  in 
  languid 
  ; 
  for 
  they 
  run 
  at 
  first 
  in 
  front 
  of 
  the 
  platform, 
  and 
  next 
  

   along 
  each 
  side 
  of 
  and 
  close 
  to 
  the 
  median 
  plate. 
  In 
  the 
  Trimerellids 
  

   and 
  in 
  Lingula 
  they 
  strike 
  directly 
  out 
  from 
  the 
  sides 
  of 
  the 
  platform, 
  

   and 
  take 
  a 
  more 
  or 
  less 
  submarginal 
  direction. 
  At 
  their 
  origin, 
  and 
  

   in 
  the 
  medio-lateral 
  region 
  of 
  Lingulops, 
  the 
  vascular 
  impressions 
  

   are 
  much 
  obscured 
  by 
  apparently 
  others 
  of 
  the 
  kind, 
  seemingly 
  nume- 
  

   rous 
  and 
  passing 
  off 
  to 
  the 
  margins. 
  The 
  ends 
  of 
  the 
  semicircular 
  zone 
  

   merge 
  into 
  the 
  same 
  regions, 
  and 
  are 
  equally 
  obscured. 
  Neither 
  our 
  

   figure, 
  nor 
  Hall's 
  gives 
  any 
  thing 
  more 
  than 
  a 
  faint 
  approximation 
  to 
  

   the 
  true 
  characters 
  and 
  grouping 
  of 
  these 
  impressions. 
  

  

  We 
  think 
  it 
  probable 
  that 
  lateral 
  muscles 
  similar 
  to 
  those 
  charac- 
  

   teristic 
  of 
  Lingula 
  were 
  implanted 
  in 
  the 
  same 
  regions. 
  Much 
  diffi- 
  

   culty 
  attaches 
  to 
  gaining 
  a 
  satisfactory 
  clue 
  to 
  the 
  similarly 
  situated 
  

   scai-s 
  in 
  the 
  Trimerellids. 
  

  

  Considerable 
  resemblance 
  prevails 
  between 
  the 
  platform 
  of 
  Tri- 
  

   merella 
  and 
  the 
  apophysis 
  of 
  Lingulops 
  in 
  their 
  outline 
  ; 
  and 
  the 
  

   resemblance 
  appears 
  to 
  be 
  equally 
  close 
  in 
  their 
  scars 
  : 
  there 
  is 
  

   apparently 
  a 
  lateral, 
  a 
  median, 
  and 
  an 
  anterior 
  pair. 
  

  

  With 
  reference 
  to 
  the 
  position 
  which 
  Lingulops 
  occupies, 
  the 
  

   characters, 
  as 
  now 
  made 
  known, 
  evidently 
  relate 
  it 
  both 
  to 
  the 
  

   Trimerellids 
  and 
  Lingulids 
  ; 
  but, 
  while 
  thus 
  affined, 
  we 
  feel 
  un- 
  

   decided 
  as 
  to 
  which 
  family 
  it 
  should 
  be 
  placed 
  in. 
  So 
  long 
  as 
  the 
  

   other 
  valve 
  remains 
  unknown 
  the 
  safest 
  plan 
  will 
  be 
  to 
  waive 
  this 
  

   subject, 
  and 
  simply 
  join 
  with 
  Hall 
  in 
  regarding 
  the 
  fossil 
  as 
  a 
  

   " 
  Linguloid 
  form." 
  

  

  Lingulops 
  Jlhitfieldi 
  is 
  stated 
  to 
  be 
  a 
  "Lower 
  Silurian 
  species;" 
  

   but 
  its 
  locality 
  has 
  not 
  been 
  mentioned, 
  further 
  than 
  that 
  it 
  is 
  in 
  

   the 
  United 
  States. 
  

  

  b. 
  CHELODEsf 
  Bergmant, 
  Davidson 
  & 
  King. 
  PI. 
  XVIII. 
  fig. 
  14, 
  

   14 
  a 
  be. 
  

  

  If 
  doubts 
  prevail 
  in 
  our 
  minds 
  as 
  to 
  the 
  family 
  to 
  which 
  Lingulops 
  

   belongs, 
  we 
  have 
  doubts 
  of 
  a 
  far 
  wider 
  bearing 
  with 
  reference 
  to 
  the 
  

   fossil 
  now 
  to 
  be 
  described. 
  Out 
  of 
  respect 
  to 
  our 
  friend 
  Dr. 
  Lindstrdm, 
  

   who, 
  believing 
  it 
  to 
  be 
  related 
  to 
  them, 
  wished 
  it 
  to 
  be 
  described 
  

   along 
  with 
  the 
  Trimerellids 
  he 
  so 
  kindly 
  placed 
  in 
  our 
  hands 
  for 
  

   description, 
  we 
  append 
  an 
  account 
  of 
  this 
  fossil. 
  As 
  it 
  possesses 
  

   some 
  characters 
  seemingly 
  resembling 
  those 
  peculiar 
  to 
  the 
  pedicle- 
  

   valve 
  of 
  a 
  Palliobranch, 
  the 
  following 
  description 
  has 
  accordingly 
  

   been 
  drawn 
  up. 
  

  

  * 
  In 
  the 
  pedicle-valve 
  of 
  Lingula 
  anatina 
  the 
  transmedial 
  muscles 
  have 
  their 
  

   attachment 
  similarly 
  situated. 
  Were 
  the 
  fossil 
  the 
  same 
  valve 
  we 
  should 
  have 
  

   had 
  little 
  hesitation 
  in 
  referring 
  the 
  lateral 
  sinuses 
  to 
  these 
  muscles, 
  notwith- 
  

   standing 
  their 
  being 
  single 
  on 
  one 
  side 
  and 
  double 
  on 
  the 
  other 
  in 
  Lingula. 
  

  

  f 
  Claw-shaped. 
  

  

  