﻿T. 
  DAVIDSON 
  AND 
  W. 
  KING 
  ON 
  THE 
  TEIMERELLID^. 
  143 
  

  

  large 
  ; 
  pointed 
  ; 
  projecting 
  variously 
  ; 
  solid, 
  or 
  hollow 
  : 
  its 
  hinge- 
  

   face 
  with 
  a 
  well-developed 
  area. 
  Area 
  usually 
  of 
  considerable 
  size 
  ; 
  

   with 
  a 
  large 
  deltidium, 
  which 
  is 
  solid 
  throughout. 
  Hinge 
  of 
  both 
  

   valves 
  rudely 
  or 
  faintly 
  dentary 
  : 
  that 
  of 
  the 
  pedicle-valve 
  thick 
  ; 
  

   entire 
  in 
  its 
  whole 
  length 
  ; 
  and 
  more 
  or 
  less 
  elevated 
  ; 
  supported 
  in 
  

   the 
  latter 
  case 
  by 
  an 
  upright 
  rib 
  or 
  cardinal 
  buttress 
  of 
  varying 
  thick- 
  

   ness 
  ; 
  with 
  a 
  wide 
  median 
  space 
  or 
  cardinal 
  facet 
  enclosing 
  a 
  lozenge- 
  

   shaped 
  scar 
  : 
  that 
  of 
  the 
  brachial 
  valve 
  with 
  a 
  more 
  or 
  less 
  elevated 
  

   median 
  prominence, 
  or 
  depression. 
  Attached 
  to 
  the 
  interior 
  surface 
  

   of 
  the 
  posterior 
  half 
  of 
  both 
  valves 
  is 
  a 
  more 
  or 
  less 
  elevated 
  plat- 
  

   form 
  ; 
  which 
  is 
  medio-longitudinally 
  situated, 
  and 
  solid, 
  or 
  doubly 
  

   vaulted 
  : 
  from 
  the 
  middle 
  of 
  its 
  anterior 
  end 
  a 
  median 
  plate 
  occa- 
  

   sionally 
  projects 
  into 
  the 
  anterior 
  half 
  of 
  the 
  valve, 
  especially 
  the 
  

   brachial 
  one. 
  Both 
  valves 
  have 
  a 
  compound 
  impression 
  or 
  crescent 
  

   running 
  a 
  little 
  within 
  the 
  margins 
  of 
  their 
  posterior 
  half, 
  including 
  

   the 
  hinge. 
  A 
  submarginal 
  impression 
  or 
  archlet 
  characterizes 
  the 
  

   other 
  or 
  anterior 
  half 
  of 
  the 
  valves. 
  

  

  The 
  detailed 
  description 
  already 
  given 
  of 
  the 
  various 
  parts 
  cha- 
  

   racteristic 
  of 
  the 
  family 
  renders 
  it 
  unnecessary 
  to 
  add 
  any 
  thing 
  by 
  

   way 
  of 
  general 
  observations. 
  Variations 
  of 
  these 
  parts, 
  to 
  a 
  con- 
  

   siderable 
  extent, 
  occur 
  in 
  the 
  whole 
  group. 
  It 
  is 
  principally 
  on 
  the 
  

   variations 
  of 
  the 
  platform, 
  and 
  other 
  parts 
  belonging 
  to 
  the 
  cardinal 
  

   region, 
  that 
  the 
  genera 
  Trimerella, 
  Monomerella 
  and 
  Dinobolus 
  are 
  

   founded. 
  As 
  in 
  other 
  families, 
  the 
  present 
  one 
  is 
  not 
  without 
  

   species 
  which 
  cannot 
  be 
  satisfactorily 
  allocated 
  generically. 
  

  

  VIII. 
  The 
  Genus 
  Teimeeella 
  and 
  its 
  Species. 
  

  

  Genus 
  Trimerella, 
  Billings, 
  1862*. 
  Obolus 
  (galtensis), 
  Billings, 
  

   1862. 
  Gotlanclia, 
  (Dall), 
  1870. 
  Rhynobolus 
  (galtensis), 
  Hall, 
  

   March 
  1871. 
  Obolellina 
  (galtensis), 
  Billings, 
  Dec. 
  1871. 
  

  

  Valves 
  thick 
  ; 
  longitudinally 
  oval. 
  Umbo 
  of 
  pedicle- 
  valve 
  usually 
  

   massive 
  ; 
  solid 
  ; 
  occasionally 
  double-chambered 
  ; 
  irregularly 
  pro- 
  

   jecting. 
  Area 
  of 
  considerable 
  size 
  ; 
  longer 
  than 
  wide. 
  Deltidium 
  

   large. 
  Hinge 
  generally 
  thick, 
  and 
  elevated; 
  rudely 
  or 
  slightly 
  

   dentary 
  ; 
  and 
  variously 
  modified 
  in 
  different 
  species. 
  Cardinal 
  facet 
  

   large. 
  Crescent 
  rather 
  well 
  defined 
  in 
  typical 
  species. 
  Platforms 
  

   elevated, 
  and 
  doubly 
  vaulted 
  ; 
  occasionally 
  solid, 
  and 
  slightly 
  raised. 
  

  

  that 
  the 
  brachial 
  appendages 
  are 
  not 
  locomotory 
  organs. 
  It 
  seems 
  probable 
  that 
  

   locomotion 
  is 
  effected 
  by 
  the 
  pedicle, 
  at 
  least 
  in 
  shells 
  in 
  the 
  young 
  state 
  : 
  this 
  

   view 
  is 
  supported 
  by 
  Morse's 
  observations 
  on 
  Lingula 
  pyramidata, 
  and 
  by 
  the 
  

   evidence 
  of 
  Stoliczka, 
  who, 
  from 
  what 
  he 
  saw 
  of 
  Lingula 
  anatina 
  on 
  the 
  coast 
  of 
  

   Arrakan, 
  is 
  inclined 
  to 
  believe 
  that 
  it 
  is 
  capable 
  of 
  changing 
  its 
  place 
  actually 
  

   by 
  movements 
  of 
  the 
  pedicle: 
  see 
  Mem. 
  Geol. 
  Survey 
  of 
  India, 
  vol. 
  iv. 
  1, 
  p. 
  5. 
  

   Blainville's 
  name, 
  Palliobranchiata, 
  is 
  unobjectionable, 
  as 
  the 
  pallial 
  lobes 
  are 
  

   the 
  principal 
  respiratory 
  organs. 
  

  

  * 
  Geological 
  Survey 
  of 
  Canada, 
  Palaeontology, 
  p. 
  166, 
  1862. 
  The 
  name 
  Tri- 
  

   merella, 
  like 
  Monomerella 
  and 
  Dinobolus, 
  is 
  unfortunately 
  not 
  above 
  criticism. 
  

  

  M 
  2 
  

  

  