﻿NO. 
  1139. 
  DEEP-WATER 
  MOLLUSCA—VEBRILL 
  AND 
  BUSH. 
  875 
  

  

  rower; 
  its 
  groove 
  is 
  narrow 
  and 
  inconspicuous. 
  The 
  hinge-margin 
  

   itself 
  is 
  rather 
  thin 
  and 
  bears 
  very 
  numerous, 
  erect, 
  V-shaped, 
  acute 
  

   teeth 
  whicli 
  number, 
  in 
  the 
  large 
  specimens, 
  about 
  sixteen 
  or 
  seventeen 
  

   in 
  the 
  anterior 
  series 
  and 
  about 
  thirty-two 
  or 
  thirty 
  three 
  in 
  the 
  poste- 
  

   rior, 
  including 
  a 
  number 
  of 
  small 
  proximal 
  ones; 
  beneath 
  the 
  beaks 
  

   there 
  is 
  a 
  smooth, 
  edentulous 
  space, 
  often 
  a 
  little 
  thickened 
  at 
  the 
  inner 
  

   margin 
  and 
  projecting 
  a 
  little 
  inward 
  in 
  the 
  middle, 
  and 
  continuing 
  

   inside 
  the 
  series 
  of 
  small 
  proximal 
  teeth 
  on 
  each 
  side. 
  In 
  some 
  cases 
  

   this 
  thickened 
  border 
  seems 
  to 
  arise 
  anteriorly 
  and 
  to 
  pass 
  under 
  

   the 
  posterior 
  series, 
  as 
  a 
  slight 
  fold; 
  in 
  other 
  cases 
  it 
  is 
  continued 
  

   directly 
  from 
  one 
  series 
  to 
  the 
  other. 
  The 
  posterior 
  series 
  is 
  nearly 
  

   straight 
  and 
  about 
  twice 
  as 
  long 
  as 
  the 
  anterior 
  wliich 
  is 
  strongly 
  

   curved 
  and 
  distallj^ 
  somewhat 
  recedes 
  from 
  the 
  thin 
  dorsal 
  margin. 
  

   The 
  anterior 
  end 
  of 
  the 
  shell 
  is 
  rather 
  short 
  and 
  evenly 
  rounded 
  ; 
  the 
  

   posterior 
  is 
  about 
  twice 
  as 
  long, 
  a 
  little 
  wider 
  owing 
  to 
  a 
  slight 
  ventral 
  

   expansion, 
  compressed 
  and 
  obtusely 
  rounded 
  or 
  subtruncated 
  at 
  the 
  

   margin, 
  but 
  without 
  any 
  distinct 
  carination 
  or 
  angulation. 
  The 
  pallia! 
  

   sinus 
  is 
  very 
  broad 
  and 
  deep, 
  extending 
  nearly 
  to 
  the 
  middle 
  of 
  the 
  

   shell. 
  The 
  inner 
  surface 
  is 
  smooth, 
  white 
  or 
  grayish 
  white. 
  The 
  

   exterior 
  is 
  smooth, 
  except 
  for 
  the 
  delicate 
  lines 
  of 
  growth, 
  and 
  covered 
  

   with 
  a 
  thin, 
  brilliantly 
  iridescent 
  epidermis 
  which, 
  in 
  live 
  specimens, 
  

   is 
  pale 
  yellowish 
  green, 
  but 
  in 
  dead 
  valves 
  is 
  pale 
  straw 
  color. 
  

  

  Our 
  larger 
  s])ecimens 
  measure 
  about 
  15 
  or 
  16 
  mm. 
  in 
  length 
  and 
  9 
  or 
  

   9.5 
  mm. 
  in 
  height. 
  

  

  Found 
  at 
  many 
  stations 
  between 
  jN^. 
  lat. 
  41° 
  28', 
  W. 
  long. 
  65° 
  35', 
  and 
  

   N. 
  lat. 
  35° 
  16', 
  W. 
  long. 
  75° 
  2' 
  30", 
  in 
  516 
  to 
  1,781 
  fathoms, 
  1883-1887. 
  

  

  MALLETIA 
  ABYSSORUM, 
  new 
  species. 
  

  

  (Plate 
  XC 
  VII, 
  fig. 
  7.) 
  

  

  Shell 
  small, 
  not 
  much 
  compressed, 
  lustrous, 
  iridescent, 
  subovate, 
  not 
  

   gaping, 
  decidedly 
  inequilateral, 
  with 
  the 
  posterior 
  end 
  the 
  longer, 
  

   broader, 
  obtusely 
  rounded, 
  without 
  any 
  distinct 
  rostration. 
  Umbos 
  

   rather 
  x)rominent, 
  rising 
  above 
  the 
  outline 
  of 
  the 
  dorsal 
  margin, 
  with 
  

   small 
  beaks 
  turned 
  backward 
  at 
  the 
  tip. 
  Lunule 
  and 
  escutcheon 
  abor- 
  

   tive. 
  The 
  short 
  antero 
  dorsal 
  margin 
  is 
  slightly 
  concave, 
  and 
  slopes 
  

   rapidly 
  to 
  the 
  slightly 
  angulated 
  anterior 
  end; 
  the 
  ventral 
  margin 
  is 
  

   very 
  broadly 
  and 
  evenly 
  convex, 
  the 
  curvature 
  receding 
  somewhat 
  pos- 
  

   teriorly, 
  so 
  that 
  the 
  greatest 
  height 
  of 
  the 
  shell 
  is 
  somewhat 
  back 
  of 
  the 
  

   middle, 
  posteriorly 
  there 
  is 
  a 
  slight 
  extension 
  of 
  the 
  edge 
  correspond- 
  

   ing 
  to 
  an 
  indistinct 
  radial 
  ridge; 
  the 
  posterior 
  end 
  is 
  very 
  broad, 
  

   obtuse, 
  not 
  angulated, 
  with 
  the 
  dorsal 
  margin 
  nearly 
  horizontal, 
  slightly 
  

   convex, 
  compressed 
  and 
  forming 
  a 
  slight 
  angle 
  where 
  it 
  joins 
  the 
  poste- 
  

   rior 
  curve. 
  A 
  very 
  slight 
  groove 
  defines 
  a 
  very 
  faint 
  escutcheon, 
  along 
  

   the 
  edge 
  of 
  which 
  the 
  teeth 
  can 
  be 
  seen 
  through 
  the 
  substance 
  of 
  the 
  

   shell. 
  The 
  surface 
  is 
  polished, 
  brilliantly 
  iridescent, 
  and 
  is 
  marked 
  by 
  

   faint, 
  raised, 
  concentric 
  lines, 
  or 
  ridges 
  parallel 
  with 
  the. 
  lines 
  of 
  growthj 
  

  

  