﻿NO. 
  1139. 
  DEEP-WATER 
  MOLLUSCA—VEREILL 
  AND 
  BUSH. 
  801 
  

  

  which 
  are 
  most 
  distinct 
  on 
  the 
  rostrum. 
  The 
  hinge-margin 
  is 
  thin. 
  

   The 
  right 
  valve 
  has 
  a 
  thin, 
  low, 
  much 
  elongated 
  i^osterior 
  lateral 
  tooth 
  

   which 
  runs 
  nearly 
  parallel 
  with 
  the 
  dorsal 
  margin, 
  above 
  which 
  it 
  pro- 
  

   jects 
  in 
  a 
  broad 
  curve; 
  the 
  cartilage-plate 
  is 
  small, 
  very 
  oblique, 
  and 
  

   closely 
  united 
  with 
  the 
  tooth 
  from 
  which 
  it 
  is 
  separated 
  by 
  a 
  faint, 
  curved 
  

   notch; 
  no 
  buttress. 
  In 
  the 
  left 
  valve 
  there 
  is 
  no 
  lateral 
  tooth, 
  and 
  the 
  

   cartilage-plate 
  is 
  very 
  small, 
  slightly 
  i^rominent, 
  with 
  a 
  curved 
  inner 
  

   edge. 
  The 
  inner 
  surface 
  of 
  the 
  shell 
  is 
  smooth 
  and 
  the 
  muscular 
  scars 
  

   are 
  faint. 
  

  

  Length 
  of 
  an 
  average 
  specimen, 
  13 
  mm. 
  ; 
  height, 
  8 
  mm. 
  ; 
  breadth, 
  6.5 
  

   mm.; 
  beak 
  to 
  end 
  of 
  rostrum, 
  8.5 
  mm.; 
  beak 
  to 
  anterior 
  end, 
  6 
  mm. 
  

  

  This 
  species 
  is 
  allied 
  to 
  C. 
  glacialis, 
  from 
  which 
  it 
  differs 
  in 
  its 
  more 
  

   swollen 
  form, 
  more 
  oblique 
  anterior 
  end, 
  more 
  prominent 
  ventral 
  mar- 
  

   gin, 
  more 
  clearly 
  defined 
  rostrum, 
  and 
  straighter 
  postero-dorsal 
  margin. 
  

   The 
  hinge 
  shows 
  still 
  more 
  decided 
  differences; 
  the 
  lateral 
  tooth 
  of 
  the 
  

   latter 
  is 
  stouter, 
  more 
  prominent, 
  and 
  less 
  prolonged; 
  the 
  cartilage- 
  

   plate 
  is 
  smaller 
  and 
  less 
  distinctly 
  defined. 
  From 
  C.f 
  rater 
  na 
  it 
  differs 
  

   in 
  being 
  less 
  produced 
  ventrally 
  and 
  in 
  having 
  a 
  longer 
  rostrum 
  with 
  

   much 
  straighter 
  dorsal 
  margin 
  and 
  a 
  much 
  longer 
  lateral 
  tooth. 
  

  

  This 
  is 
  a 
  common 
  species 
  off 
  Marthas 
  Vineyard 
  and 
  has 
  been 
  taken 
  

   at 
  about 
  fifteen 
  stations 
  between 
  N. 
  lat. 
  40° 
  10' 
  15", 
  W. 
  long. 
  70° 
  26', 
  

   andN. 
  lat. 
  39° 
  56', 
  W. 
  long. 
  70° 
  54' 
  18", 
  in 
  63 
  to 
  155 
  fathoms, 
  1880-1884. 
  

   A 
  broken 
  valve, 
  station 
  362, 
  N. 
  lat. 
  42° 
  1', 
  W. 
  long. 
  69° 
  34', 
  in 
  106 
  

   fathoms, 
  1879, 
  is 
  also 
  referred 
  to 
  this 
  species. 
  

  

  CUSPIDARIA 
  PARVA, 
  new 
  species. 
  

   (Plates 
  LXXIV, 
  fig. 
  9; 
  LXXVII, 
  fig. 
  7.) 
  

  

  Shell 
  small, 
  delicate, 
  elongated, 
  iuequivalved, 
  having 
  a 
  general 
  resem- 
  

   blance 
  in 
  form 
  to 
  the 
  very 
  young 
  of 
  C 
  obesa 
  and 
  C. 
  fraterna. 
  Umbos 
  

   small, 
  rather 
  prominent; 
  beaks 
  small 
  and 
  incurved. 
  The 
  antero-dorsal 
  

   margin 
  is 
  moderately 
  convex 
  and 
  slopes 
  regularly 
  to 
  the 
  evenly 
  rounded 
  

   anterior 
  end; 
  ventral 
  margin 
  very 
  broadly 
  rounded, 
  with 
  a 
  decided 
  

   incurvature 
  at 
  the 
  base 
  of 
  the 
  rostrum, 
  corresponding 
  to 
  the 
  marked 
  

   depression 
  of 
  the 
  surface; 
  postero-dorsal 
  margin 
  slopes 
  rapidly 
  at 
  

   first 
  and 
  is 
  usually 
  concave 
  along 
  the 
  rostrum, 
  which 
  is 
  moderately 
  

   long 
  (the 
  length 
  varies 
  in 
  different 
  specimens), 
  narrow, 
  with 
  an 
  obtusely 
  

   rounded 
  or 
  subtruncated 
  end. 
  It 
  is 
  crossed 
  by 
  a 
  distinct 
  diagonal 
  

   ridge, 
  above 
  which 
  there 
  are 
  several 
  small, 
  raised, 
  radial 
  lines; 
  the 
  

   surface 
  is 
  elsewhere 
  nearly 
  smooth 
  or 
  presents 
  a 
  microscopic, 
  faintly 
  

   granulose 
  appearance. 
  The 
  left 
  valve 
  is 
  the 
  larger 
  and 
  considerably 
  

   overlaps 
  the 
  right 
  along 
  the 
  ventral 
  margin 
  and 
  sij)honal 
  region; 
  the 
  

   right 
  overlaps 
  the 
  left 
  along 
  the 
  iiostero- 
  dorsal 
  margin; 
  the 
  rostrum 
  

   is 
  a 
  little 
  bent 
  toward 
  the 
  left 
  in 
  some 
  specimens. 
  The 
  hinge-margin 
  is 
  

   delicate, 
  with 
  the 
  anterior 
  margin 
  a 
  little 
  everted; 
  cartilage-plate 
  

   minute, 
  sunken, 
  in 
  the 
  right 
  valve 
  well 
  separated 
  from 
  the 
  prominent, 
  

   Proc, 
  N. 
  M. 
  vol. 
  XX 
  51 
  

  

  