﻿872 
  PnOCEJ'JDINGS 
  of 
  the 
  national 
  museum. 
  vol. 
  XX. 
  . 
  

  

  the 
  teeth. 
  In 
  the 
  left 
  valve, 
  there 
  are 
  eleven 
  anterior 
  and 
  nine 
  pos- 
  

   terior 
  teeth. 
  The 
  surface 
  of 
  the 
  shell 
  is 
  dull 
  yellowish 
  green, 
  only 
  

   slightly 
  iridescent, 
  and 
  covered 
  with 
  irregular 
  lines 
  of 
  growth 
  which, 
  in 
  

   some 
  places, 
  form 
  irregular 
  raised 
  lines. 
  The 
  umbos 
  are 
  but 
  little 
  

   prominent; 
  the 
  beaks 
  are 
  small 
  and 
  turn 
  backward. 
  

  

  Length, 
  3.G 
  mm.; 
  height, 
  2.5 
  mm. 
  

  

  One 
  specimen 
  (No. 
  78363), 
  station 
  2097, 
  N. 
  lat. 
  47° 
  40', 
  W. 
  long. 
  47° 
  

   35' 
  30", 
  in 
  206 
  fathoms, 
  1886. 
  

  

  This 
  species 
  is 
  peculiar 
  in 
  its 
  nearly 
  equilateral, 
  elliptical 
  form, 
  with 
  

   the 
  dorsal 
  margins 
  gently 
  convex 
  and 
  only 
  slightly 
  sloping 
  both 
  sides 
  of 
  

   the 
  beaks, 
  and 
  especially 
  in 
  its 
  large 
  resilial 
  notch 
  which 
  cuts 
  entirely 
  

   through 
  the 
  hiuge-plate. 
  It 
  agrees 
  pretty 
  closely 
  with 
  Jeffreys' 
  type, 
  

   but 
  the 
  latter 
  was 
  much 
  smaller 
  and 
  his 
  figures 
  and 
  diagnosis 
  are 
  too 
  

   imj)erfect 
  to 
  make 
  its 
  identity 
  certain. 
  

  

  YOLDIELLA 
  FRIGIDA 
  (Torell). 
  

   (Phite 
  LXXIX, 
  fig. 
  4.) 
  

  

  Yoldia 
  frigida 
  Verrill, 
  Traus. 
  Conn. 
  Acad., 
  V, 
  p. 
  573, 
  pi. 
  xliv, 
  fig. 
  2, 
  1882; 
  VI, 
  

   p. 
  279, 
  1884 
  (in 
  part) 
  ; 
  Expl. 
  Albatross, 
  Report 
  U. 
  S. 
  Com. 
  Fish 
  and 
  Fisheries 
  

   for 
  1883, 
  p. 
  576, 
  1885 
  (in 
  part). 
  

  

  A 
  very 
  few 
  specimens, 
  at 
  about 
  ten 
  stations, 
  between 
  K. 
  lat. 
  43° 
  5', 
  

   W. 
  long. 
  70° 
  11' 
  30", 
  and 
  K. 
  lat. 
  39° 
  53' 
  30", 
  W. 
  long. 
  71° 
  13' 
  30", 
  in 
  88 
  

   to 
  312 
  fathoms, 
  1874-1881. 
  

  

  YOLDIELLA 
  DISSIMILIS, 
  new 
  species. 
  

  

  (Plates 
  LXXVIII, 
  fig. 
  8; 
  LXXXII, 
  fig. 
  7.) 
  

  

  Toldia 
  expansa 
  Verrill, 
  Trans. 
  Conn. 
  Acad., 
  VI, 
  p. 
  279, 
  1884 
  ; 
  Expl. 
  Alhatross, 
  Re- 
  

   port 
  U. 
  S. 
  Com. 
  Fish 
  and 
  Fisheries 
  for 
  1883, 
  p. 
  576, 
  1885 
  (not 
  of 
  Jeffreys). 
  

  

  Shell 
  small, 
  oblong-ovate, 
  nearly 
  equilateral, 
  with 
  the 
  anterior 
  end 
  

   the 
  broader 
  and 
  bluntly 
  rounded, 
  the 
  posterior 
  end 
  somewhat 
  narrowed 
  

   medially 
  and 
  bluntly 
  rounded, 
  without 
  any 
  distinct 
  angulation. 
  Umbos 
  

   somewhat 
  prominent; 
  beaks 
  small 
  and 
  strongly 
  incurved. 
  Surface 
  

   straw-colored, 
  not 
  lustrous, 
  covered 
  with 
  fine 
  concentric 
  lines. 
  Antero- 
  

   dorsal 
  margin 
  but 
  little 
  curved, 
  sloping 
  very 
  gradually 
  to 
  the 
  anterior 
  

   end 
  which 
  is 
  curved 
  nearly 
  in 
  the 
  arc 
  of 
  a 
  circle; 
  ventral 
  margin 
  very 
  

   broadly 
  rounded 
  with 
  a 
  very 
  slight 
  obtuse 
  angulation 
  behind 
  the 
  mid- 
  

   dle; 
  j)Ostero-dorsal 
  margin 
  slightly 
  excavated 
  just 
  behind 
  the 
  beaks, 
  

   then 
  sloping 
  very 
  gradually 
  to 
  the 
  obtuse 
  posterior 
  end. 
  The 
  hinge- 
  

   margin 
  is 
  moderately 
  stout; 
  the 
  two 
  portions 
  form 
  a 
  very 
  wide 
  angle 
  

   at 
  the 
  beak 
  with 
  the 
  anterior, 
  which 
  faces 
  obliquely 
  downward, 
  consid- 
  

   erably 
  the 
  more 
  arched. 
  In 
  the 
  center 
  the 
  margin 
  becomes 
  very 
  thin 
  

   and 
  is 
  interrupted 
  by 
  the 
  resilium 
  which 
  occupies 
  a 
  deep 
  notch 
  and 
  an 
  

   internal 
  shelf 
  of 
  considerable 
  size, 
  situated 
  far 
  back 
  and 
  directed 
  down- 
  

   ward 
  to 
  such 
  an 
  extent 
  that 
  it 
  is 
  only 
  partially 
  visible 
  in 
  a 
  direct 
  front 
  

   view 
  ; 
  there 
  are 
  about 
  eleven 
  or 
  twelve 
  anterior, 
  and 
  eight 
  to 
  ten 
  poste- 
  

  

  