﻿866 
  niOCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  volxx. 
  

  

  YOLDIELLA 
  JEFFREYSI 
  (Hidalgo). 
  

  

  (Plates 
  LXXXI, 
  fif^.S; 
  LXXXIII, 
  fig. 
  3.) 
  

  

  Leda 
  lata 
  Jeffreys, 
  Ann. 
  Mag. 
  Nat. 
  Hist., 
  p. 
  431, 
  November, 
  1876. 
  

  

  Leda 
  jcjfreysi 
  Jeffreys, 
  Proc. 
  Zoill. 
  Soc. 
  London, 
  p. 
  579, 
  pi. 
  xlvi, 
  fig. 
  2, 
  June, 
  

  

  1879. 
  — 
  Smith, 
  E. 
  A., 
  Report 
  Voy. 
  Challenger, 
  Zool. 
  Lamellibranehiata, 
  XIII, 
  

  

  p. 
  234, 
  1885. 
  

   Not 
  Yoldiajejfreysi 
  Vekrili., 
  Trans. 
  Conn. 
  Acad., 
  VI, 
  p. 
  229, 
  1884. 
  

  

  Shell 
  small, 
  ovate-elliptical, 
  somewhat 
  thick 
  for 
  its 
  size, 
  rather 
  swol- 
  

   len, 
  covered 
  with 
  a 
  glossy, 
  iridescent, 
  brownish 
  yellow 
  epidermis. 
  The 
  

   posterior 
  end 
  is 
  considerably 
  the 
  longer, 
  somewhat 
  narrowed, 
  blnntly 
  

   rounded 
  without 
  any 
  distinct 
  rostrum. 
  Umbos 
  rather 
  prominent, 
  some- 
  

   what 
  swollen; 
  beaks 
  prominent, 
  curved 
  inward 
  and 
  backward. 
  The 
  

   an 
  tero 
  dorsal 
  margin 
  is 
  broadly 
  convex, 
  slopes 
  a 
  little 
  and 
  becomes 
  

   continuous 
  with 
  the 
  rather 
  regularly 
  curved 
  outline 
  of 
  the 
  rounded 
  

   anterior 
  end; 
  ventral 
  margin 
  is 
  broadly 
  and 
  regularly 
  curved 
  without 
  

   any 
  distinct 
  flexure; 
  the 
  posterior 
  end 
  is 
  obtusely 
  rounded 
  and 
  not 
  

   defined 
  by 
  any 
  radial 
  lines 
  or 
  ridges, 
  with 
  the 
  dorsal 
  margin 
  nearly 
  

   straight 
  at 
  first, 
  usually 
  slightly 
  convex 
  in 
  the 
  middle, 
  and 
  sloping 
  

   gradually. 
  The 
  surface 
  beneath 
  the 
  epidermis 
  is 
  nearly 
  smooth 
  but 
  

   shows 
  more 
  or 
  less 
  distinct 
  lines 
  of 
  growth, 
  which 
  sometimes 
  have 
  the 
  

   form 
  of 
  fine 
  parallel 
  striations. 
  The 
  hinge-plate 
  is 
  thickened 
  and 
  

   rather 
  strong; 
  the 
  two 
  series 
  of 
  teeth 
  are 
  long 
  and 
  form 
  a 
  very 
  obtuse 
  

   angle 
  at 
  the 
  beak; 
  the 
  anterior 
  is 
  somewhat 
  the 
  shorter 
  and 
  more 
  

   oblique 
  and 
  a 
  little 
  curved. 
  In 
  our 
  type 
  specimen 
  there 
  are 
  thirteen 
  

   anterior 
  teeth 
  of 
  which 
  three 
  or 
  four 
  proximal 
  ones 
  are 
  very 
  small; 
  and 
  

   fifteen 
  posterior 
  ones, 
  including 
  four 
  or 
  five 
  small 
  proximal 
  ones; 
  a 
  

   somewhat 
  larger 
  specimen 
  has 
  fifteen 
  in 
  the 
  anterior 
  series 
  and 
  eight- 
  

   een 
  in 
  the 
  posterior. 
  The 
  two 
  series 
  are 
  interrupted 
  beneath 
  the 
  beak 
  

   by 
  a 
  small, 
  well-defined, 
  concave, 
  triangular 
  resilial 
  pit 
  supported 
  on 
  

   the 
  inner 
  side 
  by 
  a 
  distinct 
  shelf-like 
  projection. 
  

  

  Length 
  of 
  the 
  type-specimen, 
  5 
  mm.; 
  height, 
  3.1 
  mm. 
  Length 
  of 
  the 
  

   largest 
  specimen, 
  5.6 
  mm. 
  ; 
  height, 
  4.2 
  mm. 
  

  

  Six 
  separate 
  valves, 
  at 
  three 
  stations, 
  between 
  N. 
  lat. 
  37° 
  38' 
  40", 
  

   W. 
  long. 
  730 
  16' 
  30", 
  and 
  N. 
  lat. 
  36° 
  42', 
  W. 
  long. 
  74° 
  30', 
  in 
  727 
  to 
  1,423 
  

   fathoms, 
  1884-1886. 
  

  

  As 
  all 
  of 
  our 
  specimens 
  are 
  much 
  larger 
  than 
  the 
  measurements 
  

   given 
  by 
  Jeffreys, 
  they 
  are 
  referred 
  to 
  Y. 
  Jeffrey 
  si 
  (Hidalgo) 
  with 
  some 
  

   doubt, 
  although 
  they 
  appear 
  to 
  agree 
  well 
  with 
  Jeffreys's 
  figure 
  of 
  that 
  

   sx^ecies 
  in 
  form 
  and 
  in 
  the 
  character 
  of 
  the 
  hinge. 
  

  

  YOLDIELLA 
  LENTICULA 
  (Moller) 
  variety 
  AMELIA, 
  new. 
  

   (Plates 
  LXXX, 
  fig. 
  9; 
  LXXXI, 
  fig. 
  4.) 
  

  

  Nucula 
  lenticula 
  Moller, 
  Ind. 
  Moll, 
  fircenl., 
  p. 
  17, 
  1842. 
  

  

  Yoldia 
  abyssicola 
  Torell, 
  Spitzbergens 
  Molluskfauna, 
  p. 
  149, 
  pi. 
  i, 
  figs. 
  4, 
  a-i, 
  

  

  1859. 
  

   Portlandia 
  lenticula 
  G. 
  O. 
  Sars, 
  Mollusca 
  Reg. 
  Arcticse 
  Norvegiaj, 
  p. 
  39, 
  pi. 
  4, 
  

  

  figs. 
  10, 
  a-l, 
  1878. 
  

   Leda 
  lenticula 
  Jeffreys, 
  Proc. 
  Zool. 
  Soc, 
  London, 
  x>. 
  577, 
  Juno, 
  1879. 
  

  

  I 
  

  

  