﻿868 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.xx. 
  

  

  YOLDIELLA 
  CURTA, 
  new 
  species. 
  

  

  (riate 
  XCVII, 
  fig. 
  8.) 
  

  

  Fhaseolus 
  ovaiu8{?) 
  Verrill, 
  Trans. 
  Conn. 
  Acad., 
  VI, 
  p. 
  230, 
  1884; 
  Expl. 
  AU,atross. 
  

   Report 
  U. 
  S. 
  Com. 
  Fish 
  and 
  Fisheries 
  for 
  1883, 
  p. 
  576, 
  1885 
  (not 
  >Seguenza). 
  

  

  Shell 
  small, 
  short 
  ovate, 
  rather 
  swollen 
  in 
  the 
  middle, 
  Avith 
  rather 
  

   prominent 
  nmbos, 
  somewhat 
  inequilateral, 
  the 
  posterior 
  end 
  the 
  longer 
  

   and 
  slightly 
  produced. 
  Beaks 
  small, 
  incurved, 
  with 
  a 
  slight 
  posterior 
  

   twist 
  and 
  a 
  little 
  separated 
  from 
  the 
  margin. 
  The 
  dorsal 
  margin 
  is 
  

   nearly 
  straight 
  medially, 
  both 
  before 
  and 
  behind 
  the 
  beaks, 
  anteriorly 
  

   it 
  merges 
  gradually 
  into 
  the 
  broatlly 
  rounded 
  anterior 
  end, 
  which 
  

   usually 
  has 
  an 
  obscure, 
  blunt 
  angulation 
  in 
  the 
  middle; 
  ventral 
  mar- 
  

   gin 
  broadly 
  and 
  evenly 
  rounded, 
  merging 
  gradually 
  into 
  the 
  more 
  

   abrupt 
  curve 
  of 
  the 
  posterior 
  end 
  which 
  is 
  a 
  little 
  tapered, 
  but 
  obtusely 
  

   rounded 
  without 
  any 
  distinct 
  rostrum 
  or 
  angulation 
  ; 
  the 
  postero-dorsal 
  

   margin 
  is 
  a 
  little 
  prominent, 
  pinched 
  up 
  and 
  convex, 
  with 
  a 
  considera- 
  

   ble 
  slope, 
  so 
  that 
  the 
  tip 
  of 
  the 
  shell 
  is 
  but 
  little 
  above 
  the 
  middle. 
  

   The 
  surface 
  is 
  polished 
  and 
  somewhat 
  iridescent, 
  marked 
  only 
  by 
  fine, 
  

   irregular 
  lines 
  of 
  growth. 
  Epidermis 
  pale 
  greenish 
  or 
  brownish 
  yellow. 
  

   There 
  is 
  a 
  relatively 
  very 
  large 
  resilium, 
  appearing 
  yoke-shaped 
  or 
  wide 
  

   W-shaped 
  in 
  the 
  separated 
  valves, 
  and 
  covering 
  a 
  relatively 
  long, 
  

   edentulous 
  space 
  beneath 
  the 
  beaks. 
  The 
  teeth 
  are 
  compressed, 
  

   oblique, 
  imperfectly 
  V-sbaped, 
  especially 
  posteriorly, 
  and 
  but 
  slightly 
  

   elevated. 
  There 
  are 
  six 
  or 
  seven 
  in 
  the 
  posterior 
  series, 
  of 
  which 
  the 
  

   l)roximal 
  ones 
  are 
  rather 
  indistinct; 
  and 
  four 
  distinct 
  and 
  two 
  or 
  three 
  

   indistinct 
  ones 
  in 
  the 
  anterior 
  series. 
  In 
  a 
  dorsal 
  view 
  five 
  are 
  visible 
  

   above 
  the 
  margin 
  behind 
  the 
  beak 
  and 
  four 
  before. 
  They 
  are 
  not 
  very 
  

   long 
  and 
  rather 
  blunt, 
  with 
  the 
  distal 
  side 
  sloping 
  and 
  the 
  side 
  next 
  

   the 
  beak 
  a 
  little 
  incurved 
  and 
  concave. 
  

  

  Length, 
  2.G 
  mm.; 
  height, 
  1.8 
  mm.; 
  thickness, 
  about 
  1 
  mm. 
  

  

  A 
  few 
  live 
  specimens, 
  at 
  three 
  stations, 
  between 
  N. 
  lat. 
  41° 
  11' 
  30", 
  

   W. 
  long. 
  660 
  12' 
  20", 
  and 
  ¥. 
  lat. 
  39° 
  38', 
  W. 
  long. 
  70° 
  22', 
  in 
  499 
  to 
  1,290 
  

   fathoms, 
  1883-188G. 
  

  

  This 
  species 
  somewhat 
  resembles 
  Y. 
  friglda 
  in 
  form, 
  but 
  it 
  is 
  rela- 
  

   tively 
  shorter, 
  higher 
  and 
  less 
  distinctly 
  rostrated. 
  Its 
  hinge 
  is 
  also 
  

   quite 
  different. 
  The 
  present 
  sppcies 
  is 
  peculiar 
  in 
  having 
  fewer 
  and 
  

   blunter 
  teeth 
  and 
  a 
  much 
  larger 
  resilium 
  than 
  most 
  of 
  the 
  related 
  

   species. 
  

  

  YOLDIELLA 
  PACHIA, 
  new 
  species. 
  

  

  Shell 
  very 
  broad, 
  oval, 
  considerably 
  swollen 
  in 
  the 
  middle, 
  with 
  the 
  

   length 
  and 
  height 
  nearly 
  equal; 
  umbos 
  rather 
  prominent. 
  The 
  poste- 
  

   rior 
  end 
  is 
  narrowed 
  and 
  slightly 
  produced, 
  but 
  not 
  defined 
  by 
  any 
  

   groove 
  or 
  carination. 
  The 
  dorsal 
  margin 
  is 
  very 
  obtusely 
  angulated, 
  

   anteriorly 
  it 
  is 
  convex 
  and 
  slopes 
  pretty 
  rapidly 
  to 
  the 
  broadly 
  and 
  

   evenly 
  rounded 
  anterior 
  end; 
  posteriorly 
  it 
  is 
  nearly 
  straight 
  at 
  first, 
  

   then 
  slopes 
  gradually 
  to 
  the 
  posterior 
  end. 
  The 
  ventral 
  margin 
  is 
  very 
  

  

  