﻿NO. 
  1139. 
  DEEP-WATER 
  MOLLUSC 
  A— 
  VEBRILL 
  AND 
  BUSH. 
  705 
  

  

  AXINOPSIS 
  CORDATA, 
  new 
  species. 
  

   (Plate 
  XCVII, 
  figs. 
  5, 
  6.) 
  

  

  Shell 
  small, 
  white, 
  smoothish, 
  rounded 
  or 
  somewhat 
  cordate, 
  longer 
  

   anteriorly, 
  with 
  small, 
  little 
  prominent 
  beaks 
  curving 
  forward. 
  Autero- 
  

   dorsal 
  margin 
  a 
  little 
  convex, 
  sloping 
  gradually 
  and 
  passing 
  somewhat 
  

   abruptly 
  into 
  the 
  anterior 
  margin, 
  which 
  is 
  broadly 
  and 
  obtusely 
  

   rounded; 
  ventral 
  margin 
  strongly 
  convex, 
  somewhat 
  produced 
  in 
  the 
  

   middle; 
  posterior 
  margin 
  pretty 
  evenly 
  rounded, 
  except 
  in 
  the 
  middle, 
  

   where 
  there 
  is 
  a 
  slightly 
  produced 
  portion 
  corresponding 
  to 
  the 
  plica- 
  

   tion; 
  postero- 
  dorsal 
  margin 
  strongly 
  convex 
  in 
  the 
  middle. 
  The 
  sur- 
  

   face 
  is 
  marked 
  by 
  flue, 
  microscopic, 
  concentric 
  stria? 
  and 
  irregular 
  lines 
  

   of 
  growth 
  which, 
  on 
  the 
  umbo, 
  appear 
  as 
  slight 
  undulations. 
  The 
  liga- 
  

   meutal 
  area 
  is 
  relatively 
  large, 
  prominent 
  in 
  the 
  middle, 
  and 
  deflned 
  by 
  

   a 
  distinct 
  groove, 
  beyond 
  which 
  there 
  is 
  a 
  well 
  marked 
  but 
  low 
  radiat- 
  

   ing 
  ridge 
  or 
  plication 
  which 
  forms 
  an 
  inconspicuous 
  projection 
  at 
  the 
  

   margin 
  ; 
  anterior 
  to 
  this 
  there 
  is 
  a 
  very 
  slight 
  wave-like 
  depression 
  of 
  

   the 
  surface, 
  much 
  as 
  in 
  most 
  species 
  of 
  Cnjptodon. 
  The 
  hinge-margin 
  

   is 
  decidedly 
  thickened; 
  in 
  both 
  valves 
  there 
  is 
  a 
  rather 
  large, 
  obtuse 
  

   tooth 
  .iust 
  below 
  the 
  beak, 
  from 
  which 
  it 
  is 
  separated 
  by 
  a 
  rather 
  large 
  

   space 
  for 
  the 
  ligament 
  which 
  runs 
  backward 
  for 
  a 
  short 
  distance 
  in 
  a 
  

   conspicuous 
  submargiual 
  groove, 
  becoming 
  internal 
  distally; 
  anteriorly 
  

   the 
  groove 
  is 
  narrow 
  and 
  outside 
  the 
  margin. 
  

  

  Length, 
  about 
  2 
  mm.; 
  height, 
  the 
  same. 
  

  

  This 
  si)ecies 
  is 
  referred 
  to 
  the 
  genus 
  Axmopsis 
  with 
  some 
  doubt, 
  

   although 
  it 
  has 
  the 
  distinct 
  cardinal 
  tooth 
  and 
  ligament 
  gi'oove. 
  It 
  

   has, 
  however, 
  a 
  single 
  posterior 
  i^lication 
  similar 
  to 
  that 
  seen 
  in 
  some 
  

   species 
  of 
  Crijptodon; 
  but 
  the 
  character 
  of 
  the 
  plications 
  vary 
  in 
  that 
  

   genus, 
  in 
  some 
  cases 
  being 
  very 
  strong 
  and 
  in 
  others 
  obsolete, 
  or 
  nearly 
  

   so. 
  In 
  fact, 
  the 
  g^nviB 
  AxinopsiH 
  can 
  hardly 
  be 
  distinguished 
  from 
  it 
  

   except 
  by 
  the 
  distinctly 
  developed 
  cardinal 
  tooth, 
  which 
  is 
  only 
  par- 
  

   tially 
  differentiated 
  from 
  the 
  proximal 
  end 
  of 
  the 
  anterior 
  hinge-plate. 
  

  

  A 
  few 
  separate 
  valves 
  and 
  two 
  live 
  young 
  were 
  found 
  at 
  six 
  stations 
  

   between 
  i^. 
  lat. 
  40°, 
  W. 
  long. 
  71° 
  14' 
  30", 
  and 
  N. 
  lat. 
  35° 
  42', 
  W. 
  long. 
  

   740 
  54' 
  30", 
  in 
  43 
  to 
  202 
  fathoms, 
  1880-1884. 
  

  

  The 
  young 
  specimens 
  from 
  stations 
  870 
  and 
  943 
  are 
  referred 
  to 
  this 
  

   f-pecies 
  with 
  considerable 
  doubt, 
  as 
  they 
  have 
  a 
  much 
  more 
  rounded 
  

   outline, 
  although 
  the 
  hinge-margin 
  is 
  similar. 
  

  

  AXINODON, 
  new 
  genus. 
  

  

  Type. 
  — 
  Axinodon 
  ellipticus, 
  new 
  species. 
  

  

  Shell 
  thin, 
  rounded 
  or 
  ovate, 
  without 
  plications. 
  Hinge 
  with 
  one 
  or 
  

   two 
  small 
  or 
  subrudimentary 
  teeth. 
  Ligament 
  internymphal, 
  poste- 
  

   riorly 
  so 
  far 
  internal 
  that 
  its 
  inner 
  end, 
  distally, 
  is 
  attached 
  below 
  the 
  

   inner 
  edge 
  of 
  the 
  hinge-plate, 
  and 
  therefore 
  covers 
  its 
  entire 
  breadth. 
  

  

  