﻿NO. 
  1139. 
  DEEP-WATER 
  MOLLVSCA—VEREILL 
  AND 
  BUSH. 
  879 
  

  

  nearly 
  straight, 
  the 
  less 
  oblique 
  and 
  considerably 
  the 
  longer, 
  and 
  forms 
  

   a 
  broad 
  angle 
  with 
  the 
  anterior. 
  There 
  are 
  in 
  the 
  largest 
  examples 
  

   about 
  eleven 
  or 
  twelve 
  teeth 
  in 
  the 
  anterior 
  series, 
  counting 
  four 
  or 
  

   five 
  very 
  small 
  proximal 
  ones; 
  and 
  in 
  the 
  posterior 
  series, 
  fifteen 
  or 
  

   sixteen 
  teeth 
  of 
  which 
  the 
  five 
  or 
  six 
  proximal 
  ones 
  are 
  minute. 
  In 
  

   many 
  si)ecimens 
  the 
  two 
  series 
  are 
  not 
  distinctly 
  separated 
  under 
  the 
  

   beak, 
  in 
  others 
  there 
  is 
  a 
  very 
  minute, 
  edentulous 
  space 
  in 
  line 
  with 
  

   the 
  minute 
  ligamental 
  notch. 
  The 
  largest 
  teeth 
  in 
  the 
  middle 
  of 
  each 
  

   series 
  are 
  very 
  elongated, 
  erect, 
  acute, 
  with 
  the 
  tips 
  turned 
  upward 
  

   toward 
  the 
  margin. 
  The 
  surface 
  of 
  the 
  shell 
  is 
  covered 
  with 
  very 
  

   regular, 
  concentric 
  sulcations 
  separated 
  by 
  narrow, 
  evenly 
  rounded 
  

   ridges 
  of 
  about 
  the 
  same 
  width; 
  in 
  most 
  cases 
  this 
  sculpture 
  is 
  

   faint 
  or 
  nearly 
  obsolete 
  toward 
  the 
  postero-dorsal 
  margin 
  and 
  on 
  the 
  

   umbos. 
  In 
  many 
  specimens, 
  a 
  number 
  of 
  faint 
  radiating 
  striji? 
  run 
  

   from 
  the 
  umbos 
  to 
  the 
  antero-ventral 
  margin, 
  similar 
  lines 
  sometimes 
  

   occur 
  posteriorly. 
  The 
  epidermis 
  is 
  without 
  much 
  luster, 
  of 
  either 
  

   greenish 
  yellow, 
  light 
  yellow, 
  or 
  straw 
  color, 
  more 
  or 
  less 
  iridescent, 
  

   especially 
  near 
  the 
  umbos. 
  Along 
  the 
  dorsal 
  margin 
  the 
  outline 
  of 
  

   the 
  teeth 
  can 
  be 
  imperfectly 
  seen 
  through 
  the 
  substan'ce 
  of 
  the 
  shell. 
  

   The 
  interior 
  in 
  fresh 
  specimens 
  is 
  lustrous 
  bluish 
  white 
  and 
  in 
  some 
  

   cases 
  is 
  distinctly 
  tinged 
  with 
  pale 
  flesli-color. 
  The 
  muscular 
  and 
  pal- 
  

   lial 
  impressions 
  are 
  usually 
  indistinct 
  but 
  some 
  specimens 
  show 
  a 
  small, 
  

   but 
  distinct, 
  angular 
  pallial 
  sinus. 
  

  

  The 
  alcoholic 
  specimens 
  when 
  dissected 
  were 
  found 
  to 
  have 
  a 
  short 
  

   siphon 
  and 
  a 
  large, 
  stout 
  foot 
  with 
  a 
  broad 
  disk 
  having 
  strongly 
  cren- 
  

   ulated 
  edges. 
  The 
  labial 
  palpi 
  were 
  long, 
  crescent-shaped 
  and 
  the 
  

   tentacle-like 
  appendages 
  arising 
  from 
  the 
  outer 
  bases 
  of 
  the 
  external 
  

   palpi 
  were 
  very 
  long, 
  slender, 
  and 
  coiled 
  in 
  a 
  spiral. 
  The 
  gills 
  Avere 
  

   long, 
  narrow, 
  and 
  prismatic, 
  one 
  on 
  each 
  side. 
  

  

  Length 
  of 
  one 
  of 
  the 
  largest 
  specimens, 
  6.5 
  mm. 
  ; 
  height, 
  4.6 
  mm. 
  ; 
  

   thickness, 
  about 
  3.5 
  mm. 
  

  

  Young 
  specimens 
  about 
  2 
  mm. 
  long 
  are 
  more 
  equilateral 
  than 
  the 
  

   adults 
  and 
  have 
  the 
  i)osterior 
  end 
  less 
  produced 
  and 
  more 
  evenly 
  

   rounded, 
  the 
  umbos 
  decidedly 
  prominent, 
  and 
  the 
  surface 
  covered 
  with 
  

   fine, 
  regular, 
  concentric 
  grooves, 
  the 
  epidermis 
  showing 
  distinct 
  iri- 
  

   descence. 
  

  

  Found 
  in 
  large 
  numbers, 
  at 
  many 
  stations, 
  between 
  N. 
  lat. 
  42° 
  47', 
  W. 
  

   long. 
  61° 
  4', 
  and 
  N. 
  lat. 
  35° 
  9' 
  50", 
  W. 
  long. 
  74° 
  57' 
  40", 
  in 
  125i 
  to 
  1,731 
  

   fathoms, 
  1883-1887. 
  

  

  This 
  species 
  shows 
  considerable 
  variation 
  in 
  form 
  when 
  a 
  large 
  series 
  

   of 
  specimens 
  from 
  the 
  same 
  locality 
  are 
  compared. 
  Some 
  are 
  decidedly 
  

   more 
  elongated 
  and 
  tapered 
  posteriorly 
  than 
  the 
  typical 
  form, 
  others 
  

   are 
  somewhat 
  shorter 
  and 
  more 
  regularly 
  ovate 
  with 
  the 
  posterior 
  end 
  

   blunter 
  or 
  more 
  rounded 
  ; 
  all 
  agree 
  essentially 
  in 
  sculpture 
  and 
  in 
  the 
  

   peculiar 
  structure 
  of 
  the 
  hinge 
  and 
  ligament. 
  

  

  This 
  species 
  has 
  some 
  resemblance 
  to 
  N. 
  sericea 
  Jeffreys, 
  of 
  which 
  it 
  

  

  