﻿782 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.xx. 
  

  

  MONTACUTA 
  CUNEATA, 
  new 
  species. 
  

   (Phites 
  XCI, 
  tig. 
  4; 
  XCIII, 
  fig. 
  .".) 
  

  

  Shell 
  simall, 
  elongated, 
  wedge-shaped, 
  with 
  a 
  much 
  produced, 
  narrow 
  

   anterior 
  end, 
  and 
  with 
  the 
  dorsal 
  margins 
  nearly 
  straight, 
  sloping 
  rap- 
  

   idly, 
  and 
  forming 
  an 
  obtuse 
  angle 
  at 
  the 
  beaks, 
  which 
  are 
  decidedly 
  

   behind 
  the 
  middle, 
  prominent, 
  curved 
  inward. 
  Antero-dorsal 
  margin 
  

   sloping 
  rapidly, 
  at 
  first 
  nearly 
  straight, 
  becoming 
  a 
  little 
  convex, 
  and 
  

   curving 
  regularly 
  into 
  the 
  ventral 
  margin, 
  thus 
  forming 
  a 
  somewhat 
  

   rostrated, 
  narrow, 
  evenly 
  rounded 
  anterior 
  end; 
  ventral 
  margin 
  nearly 
  

   straight, 
  sometimes 
  with 
  a 
  slight 
  incurvature 
  opposite 
  the 
  beaks 
  ; 
  poste- 
  

   rior 
  end 
  bluntly 
  rounded, 
  with 
  its 
  dorsal 
  margin 
  nearly 
  straight, 
  sloping 
  

   about 
  equally 
  with 
  the 
  anterior. 
  The 
  surface 
  is 
  covered 
  with 
  line, 
  con- 
  

   centric, 
  rather 
  regular 
  lines 
  of 
  growth 
  and 
  microscopic 
  striations. 
  Inte- 
  

   rior 
  somewhat 
  shining. 
  In 
  the 
  right 
  valve 
  there 
  are 
  two 
  well-defined, 
  

   prominent, 
  thickened 
  teeth, 
  separated 
  by 
  a 
  large, 
  deep 
  notch 
  under 
  the 
  

   beak; 
  the 
  anterior 
  one 
  is 
  the 
  larger 
  and 
  is 
  broadly 
  triangular, 
  with 
  a 
  

   prominent 
  excurved 
  tip, 
  and 
  is 
  separated 
  from 
  the 
  hinge-margin 
  by 
  a 
  

   deep 
  furrow, 
  which 
  runs 
  obliquely 
  within 
  and 
  below 
  the 
  thickened 
  dorsal 
  

   margin; 
  the 
  posterior 
  one 
  is 
  set 
  obliquely 
  to 
  the 
  margin, 
  from 
  which 
  it 
  

   is 
  separated 
  by 
  a 
  well-defined 
  groove. 
  In 
  the 
  left 
  valve 
  there 
  is 
  a 
  wide 
  

   notch 
  beneath 
  the 
  beak, 
  with 
  a 
  rather 
  inconspicuous, 
  elongated, 
  some- 
  

   what 
  thickened 
  anterior 
  tooth-like 
  projection, 
  which 
  continues 
  forward 
  

   as 
  a 
  thickened 
  inner 
  margin 
  nearly 
  to 
  the 
  end, 
  and 
  a 
  shorter, 
  broad, 
  

   triangular 
  posterior 
  projection. 
  Color 
  cream-white, 
  sometimes 
  tinged 
  

   with 
  pink. 
  

  

  Length 
  of 
  the 
  largest 
  specimen, 
  about 
  3 
  ram.; 
  height, 
  I..") 
  mm. 
  

  

  A 
  few 
  specimens 
  were 
  found 
  ofl" 
  Cape 
  Hatteras, 
  North 
  Carolina, 
  in 
  

   15 
  and 
  16 
  fathoms, 
  1883-84. 
  

  

  MONTACUTA 
  TRIQUETRA, 
  new 
  species. 
  

  

  (PliiteXCI, 
  fig. 
  3.) 
  

  

  Shell 
  small, 
  covered 
  with 
  regular 
  concentric 
  grooves, 
  scarcely 
  com- 
  

   pressed, 
  somewhat 
  triangular, 
  with 
  a 
  slightly 
  rostrated, 
  angular 
  posterior 
  

   end, 
  and 
  a 
  regularly 
  rounded 
  anterior 
  one. 
  Umbos 
  a 
  little 
  swollen, 
  

   beaks 
  nearly 
  central, 
  pointed 
  and 
  a 
  little 
  prominent. 
  The 
  anterior 
  and 
  

   posterior 
  dorsal 
  margins 
  form 
  nearly 
  a 
  right 
  angle; 
  the 
  anterior 
  margin 
  

   is 
  slightly 
  convex 
  and 
  j^asses 
  gradually 
  into 
  the 
  somewhat 
  bluntly 
  

   rounded 
  anterior 
  end; 
  ventral 
  margin 
  broadly 
  convex, 
  becoming 
  

   slightly 
  incurved 
  toward 
  the 
  i)osterior 
  rostration, 
  which 
  is 
  wedge- 
  

   shiiped, 
  rapidly 
  tapered, 
  with 
  a 
  narrow 
  truncate 
  tip, 
  defined 
  below 
  by 
  

   a 
  faint, 
  radiating 
  ridge; 
  i)Ostero-dorsal 
  margin 
  is 
  nearly 
  straight, 
  and 
  

   slopes 
  rapidly 
  from 
  the 
  beaks. 
  The 
  surface 
  is 
  sculptured 
  with 
  strongly 
  

   marked, 
  smooth, 
  rounded, 
  concentric 
  ridges 
  having 
  the 
  upper 
  edge 
  

   smooth 
  and 
  recurved; 
  these 
  are 
  separated 
  by 
  deep, 
  regular 
  grooves 
  

  

  