﻿168 
  T. 
  DAVIDSON 
  AND 
  W. 
  KING 
  ON 
  THE 
  TRIMEBELEID^). 
  

  

  Pedicle-valve 
  thick, 
  claw-shaped, 
  slightly 
  geniculated 
  across 
  the 
  

   middle 
  : 
  the 
  geniculation 
  forms 
  the 
  hase 
  of 
  the 
  beak, 
  which 
  is 
  a 
  little 
  

   less 
  than 
  half 
  the 
  length 
  of 
  the 
  valve, 
  and 
  almost 
  an 
  equilateral 
  tri- 
  

   angle 
  in 
  outline. 
  One 
  face 
  of 
  the 
  beak 
  is 
  flatly 
  convex, 
  and 
  slightly 
  

   lineated 
  transversely 
  : 
  the 
  opposite 
  face 
  or 
  area 
  is 
  concave, 
  and 
  

   crossed 
  by 
  rather 
  strong 
  curving 
  lines. 
  The 
  other 
  half 
  of 
  the 
  fossil 
  

   has 
  parallel 
  lateral 
  margins, 
  and 
  a 
  squarish 
  end 
  with 
  a 
  slight 
  sinus 
  

   in 
  its 
  middle. 
  One 
  face, 
  the 
  external 
  one, 
  is 
  flatly 
  convex, 
  and 
  

   marked 
  with 
  regular 
  and 
  rather 
  distinct 
  lines 
  of 
  growth 
  running 
  

   parallel 
  to 
  the 
  end. 
  The 
  opposite 
  face 
  or 
  cavity 
  has 
  an 
  outline 
  

   formed 
  by 
  the 
  sides 
  and 
  end 
  of 
  the 
  convex 
  face, 
  also 
  by 
  the 
  curved 
  

   basal 
  side 
  (or 
  hinge) 
  of 
  the 
  area 
  : 
  its 
  surface 
  has 
  two 
  slightly 
  raised 
  

   oval 
  tracts 
  situated 
  one 
  on 
  each 
  side, 
  separated 
  for 
  the 
  most 
  part 
  by 
  

   a 
  medio-longitudinal 
  hour-glass-shaped 
  furrow, 
  and 
  united 
  by 
  an 
  

   arcuated 
  band 
  lying 
  near 
  and 
  parallel 
  to 
  the 
  hinge 
  : 
  the 
  oval 
  tracts 
  

   are 
  marked 
  by 
  curving 
  subdivided 
  ribs; 
  and 
  the 
  uniting 
  band 
  is 
  

   somewhat 
  tuberculated. 
  The 
  hinge 
  is 
  thin, 
  undercut, 
  and 
  marked 
  

   in 
  the 
  middle 
  by 
  a 
  pointed 
  tooth-like 
  process; 
  which 
  has 
  been 
  

   inadvertently 
  omitted 
  in 
  fig. 
  14. 
  

  

  There 
  is 
  something 
  in 
  favour 
  of 
  this 
  singular 
  fossil 
  being 
  related 
  

   to 
  Trimerella. 
  Its 
  general 
  form 
  does 
  not 
  depart 
  much 
  from 
  that 
  

   of 
  T. 
  Billingsii 
  and 
  T. 
  galtensis. 
  The 
  same 
  may 
  be 
  said 
  of 
  the 
  

   " 
  beak." 
  The 
  " 
  area," 
  it 
  is 
  true, 
  shows 
  no 
  appearance 
  of 
  a 
  del- 
  

   tidium 
  ; 
  but 
  it 
  may 
  be 
  surmised 
  that 
  this 
  part 
  has 
  been 
  developed 
  at 
  

   the 
  expense 
  and 
  obliteration 
  of 
  the 
  areal 
  borders, 
  — 
  a 
  tendency 
  of 
  the 
  

   kind 
  being 
  displayed 
  in 
  several 
  Trimerellas. 
  The 
  " 
  hinge 
  " 
  is 
  thin, 
  

   and 
  projecting 
  or 
  ledge-shaped 
  — 
  not 
  an 
  improbable 
  modification 
  ; 
  

   and 
  it 
  has 
  actually 
  a 
  central 
  V-shaped 
  projection 
  (the 
  " 
  pointed 
  

   tooth-like 
  process 
  "), 
  reminding 
  one 
  of 
  the 
  curving 
  middle 
  that 
  cha- 
  

   racterises 
  the 
  crown 
  of 
  the 
  crescent 
  in 
  the 
  pedicle- 
  valve. 
  Even 
  the 
  

   characters 
  belonging 
  to 
  the 
  cavity 
  may 
  be 
  considered 
  as 
  placing 
  this 
  

   fossil 
  among 
  the 
  Palliobranchs, 
  inasmuch 
  as 
  the 
  lateral 
  tracts 
  have 
  

   a 
  striking 
  resemblance 
  to 
  the 
  convoluted 
  impressions 
  representing 
  

   the 
  labial 
  appendages, 
  such 
  as 
  are 
  seen 
  in 
  Bavidsonia, 
  certain 
  Spiri- 
  

   fers, 
  and 
  Productuses. 
  The 
  curved 
  connecting 
  band 
  might 
  be 
  sup- 
  

   posed 
  to 
  represent 
  the 
  highly 
  muscular 
  portion 
  forming 
  the 
  base 
  of 
  

   the 
  arms. 
  Still, 
  notwithstanding 
  these 
  remarkable 
  points 
  of 
  resem- 
  

   blance, 
  it 
  is 
  our 
  opinion 
  that 
  Chelodes 
  Bergmani 
  is 
  not 
  a 
  Palliobranch 
  : 
  

   on 
  the 
  contrary, 
  we 
  are 
  strongly 
  inclined 
  to 
  the 
  belief 
  that 
  it 
  belongs 
  

   to 
  a 
  section 
  of 
  the 
  Ccelenterates, 
  represented 
  by 
  Galceola 
  and 
  Gonio- 
  

   phyllum. 
  In 
  contending 
  for 
  this 
  position 
  we 
  are 
  unfortunately 
  at 
  

   issue 
  with 
  Dr. 
  Lindstrom, 
  than 
  whom 
  no 
  one 
  has 
  paid 
  so 
  much 
  atten- 
  

   tion 
  to 
  the 
  section 
  in 
  question 
  : 
  nevertheless, 
  feeling 
  that 
  our 
  view 
  

   requires 
  more 
  than 
  an 
  incidental 
  notice, 
  we 
  hope 
  to 
  be 
  able 
  to 
  publish 
  

   a 
  paper 
  on 
  another 
  occasion 
  giving 
  our 
  reasons 
  for 
  maintaining 
  it. 
  

  

  Chelodes 
  Bergmani 
  was 
  discovered 
  by 
  Herr 
  Bergman, 
  to 
  whom 
  we 
  

   dedicate 
  it, 
  at 
  Klinteberg 
  (a 
  hill 
  about 
  120 
  Swedish 
  feet 
  above 
  the 
  

   sea), 
  Isle 
  of 
  Gotland, 
  in 
  the 
  central 
  Gotland 
  formation, 
  — 
  an 
  equi- 
  

   valent 
  in 
  age 
  to 
  the 
  Aymestry 
  limestone 
  of 
  England. 
  

  

  