﻿No.iKfg. 
  DEEP-WATER 
  MOLLUSC 
  A— 
  VERRILL 
  AND 
  BUSH. 
  797 
  

  

  This 
  genus 
  differs 
  from 
  Cryptodon 
  in 
  the 
  more 
  internal 
  position 
  of 
  

   the 
  ligament 
  aud 
  in 
  having 
  distinct 
  lateral 
  teeth. 
  From 
  Axmodon, 
  in 
  

   the 
  stronger 
  hinge-plate, 
  in 
  the 
  presence 
  of 
  the 
  lateral 
  teeth, 
  in 
  having 
  

   a 
  posterior 
  plication, 
  aud 
  in 
  lacking 
  distinct 
  cardinal 
  teeth. 
  

  

  LEPTAXINUS 
  MINUTUS, 
  new 
  species. 
  

   (Plate 
  LXXXIX, 
  tigs. 
  C-5.) 
  

  

  Shell 
  minute, 
  broadly 
  ovate, 
  with 
  a 
  slightly 
  produced 
  obtuse 
  point 
  

   near 
  the 
  middle 
  of 
  the 
  posterior 
  end, 
  and 
  a 
  somewhat 
  produced, 
  

   broadly 
  rounded 
  anterior 
  end. 
  Beaks 
  behind 
  the 
  middle, 
  rising 
  a 
  little 
  

   above 
  the 
  dorsal 
  margin 
  aud 
  turned 
  forward, 
  leaving 
  a 
  small, 
  rather 
  

   deep 
  luuular 
  area. 
  Antero-dorsal 
  margin 
  a 
  little 
  convex, 
  sloping 
  but 
  

   little; 
  anterior 
  margin 
  broadly 
  aud 
  evenly 
  rounded, 
  forming 
  nearly 
  a 
  

   semicircle, 
  and 
  passing 
  continuously 
  into 
  the 
  ventral 
  uiargiu, 
  which 
  

   is 
  a 
  little 
  more 
  broadly 
  rounded 
  ; 
  the 
  posterior 
  margin 
  is 
  somewhat 
  

   angular, 
  with 
  a 
  distinct 
  prominence 
  a 
  little 
  below 
  the 
  middle, 
  where 
  

   the 
  radial 
  ridge 
  terminates, 
  below 
  this 
  for 
  a 
  short 
  space 
  the 
  mar- 
  

   gin 
  is 
  nearly 
  straight 
  or 
  slightly 
  incurved; 
  above, 
  the 
  postero-dorsal 
  

   margin 
  is 
  straight 
  as 
  far 
  as 
  a 
  slight 
  angle 
  in 
  the 
  ligamental 
  area, 
  above 
  

   which 
  it 
  is 
  convex 
  to 
  the 
  beak. 
  The 
  hinge-margin 
  is 
  a 
  little 
  thickened, 
  

   and 
  in 
  the 
  left 
  valve 
  forms 
  a 
  rather 
  prominent 
  and 
  somewhat 
  angular 
  

   tooth 
  just 
  below 
  aud 
  slightly 
  in 
  front 
  of 
  the 
  beak 
  ; 
  the 
  ligamental 
  groove 
  

   is 
  barely 
  visible 
  ou 
  the 
  inner 
  face 
  of 
  the 
  posterior 
  hinge-margin, 
  and 
  

   runs 
  forward 
  as 
  a 
  narrow 
  groove 
  beneath 
  the 
  beak; 
  in 
  the 
  r;ght 
  valve 
  

   there 
  is 
  a 
  somewhat 
  less 
  prominent 
  tooth 
  just 
  under 
  the 
  beak, 
  behind 
  

   which 
  the 
  ligamental 
  groove 
  forms 
  a 
  distinct 
  notch 
  in 
  the 
  margin. 
  

   Under 
  the 
  microscope 
  there 
  is 
  seen 
  in 
  both 
  valves 
  a 
  distinct 
  subniargi- 
  

   nal 
  ridge 
  with 
  a 
  consi)icuous 
  groove 
  beliiud 
  it, 
  commencing 
  a 
  consider- 
  

   able 
  distance 
  behind 
  the 
  beak 
  and 
  running 
  in 
  and 
  along 
  the 
  inner 
  

   hinge-margin; 
  there 
  is 
  also 
  in 
  the 
  right 
  valve 
  a 
  short, 
  indistinct 
  groove 
  

   along 
  the 
  end 
  of 
  the 
  hinge-margin 
  in 
  front 
  of 
  the 
  beak. 
  Externally 
  a 
  

   rather 
  shallow, 
  depressed 
  undulation 
  runs 
  from 
  the 
  beak 
  to 
  the 
  pos- 
  

   tero-ventral 
  margin; 
  behind 
  it 
  is 
  a 
  narrow, 
  but 
  slightly 
  jirominent, 
  

   radial 
  ridge 
  running 
  to 
  the 
  posterior 
  angle; 
  back 
  of 
  or 
  above 
  this 
  a 
  

   rather 
  short 
  ligamental 
  area 
  projects 
  beyond 
  the 
  margin. 
  The 
  surface 
  

   is 
  covered 
  with 
  a 
  thin, 
  greenish 
  yellow 
  epidermis 
  and 
  is 
  marked 
  by 
  

   tine, 
  pretty 
  regular, 
  parallel, 
  raised 
  lines 
  of 
  growth, 
  and 
  also 
  faint 
  and 
  

   rather 
  numerous 
  radiating 
  lines 
  which 
  are 
  not 
  visible 
  except 
  under 
  a 
  

   high 
  power. 
  

  

  Length, 
  nearly 
  2 
  mm.; 
  height, 
  If 
  mm. 
  

  

  One 
  live 
  specimen 
  (Xo. 
  45080), 
  station 
  949, 
  N. 
  lat. 
  40° 
  3', 
  W. 
  long. 
  70° 
  

   31', 
  in 
  100 
  fathoms, 
  1881. 
  

  

  