﻿NO. 
  1139. 
  DEEP- 
  WA 
  TER 
  MOLL 
  USCA— 
  VERBILL 
  AND 
  B 
  USE. 
  863 
  

  

  W. 
  long. 
  69° 
  22', 
  and 
  K. 
  lat. 
  35° 
  12' 
  10", 
  W. 
  long. 
  74° 
  57' 
  15", 
  in 
  22 
  to 
  

   516 
  fiithoms, 
  1872-1885. 
  

  

  The 
  most 
  prominent 
  character 
  of 
  this 
  species 
  is 
  the 
  relatively 
  large 
  

   size 
  of 
  the 
  cartilage-pit 
  which 
  intersects 
  both 
  the 
  hinge-margins 
  and 
  

   the 
  beaks 
  and 
  is 
  therefore 
  plainly 
  visible 
  from 
  the 
  exterior. 
  In 
  outline 
  

   it 
  is 
  similar 
  to 
  T. 
  iris 
  and 
  1". 
  inflata 
  but 
  is 
  more 
  pointed 
  and 
  narrower 
  

   posteriorly 
  than 
  either 
  of 
  them. 
  They 
  dift'er 
  also 
  in 
  having 
  much 
  

   smaller 
  cartilage-pits 
  and 
  in 
  the 
  number 
  of 
  the 
  teeth. 
  

  

  Specimens 
  formerly 
  identified 
  as 
  Toldia 
  obesa 
  Stimpson, 
  agree 
  per- 
  

   fectly 
  with 
  authentic 
  specimens 
  of 
  lucida 
  sent 
  by 
  Doctor 
  Friele 
  from 
  

   Spitzbergen. 
  As 
  none 
  of 
  the 
  species 
  known 
  to 
  us 
  agree 
  sufficiently 
  

   well 
  with 
  the 
  description 
  and 
  figure 
  of 
  Leda 
  obesa 
  Stimj)son, 
  for 
  us 
  to 
  

   decide 
  definitely 
  as 
  to 
  its 
  correct 
  position, 
  unless 
  we 
  are 
  to 
  consider 
  

   the 
  figure 
  a 
  very 
  incorrect 
  representation, 
  we 
  prefer 
  to 
  let 
  it 
  remain 
  

   doubtfully, 
  as 
  a 
  synonym 
  of 
  T. 
  lucida, 
  where 
  Jeffreys 
  and 
  others 
  have 
  

   placed 
  it. 
  

  

  YOLDIELLA 
  IRIS, 
  new 
  species. 
  

   (Plates 
  LXXX, 
  figs. 
  1, 
  2; 
  LXXXII, 
  fig. 
  11.) 
  

  

  Shell 
  small, 
  thin, 
  rather 
  delicate, 
  long-ovate 
  or 
  ovate-elliptical, 
  with 
  

   the 
  beaks 
  in 
  front 
  of 
  the 
  middle, 
  not 
  much 
  swollen; 
  surface 
  smooth, 
  or 
  

   nearly 
  so, 
  with 
  brilliant 
  iridescence. 
  The 
  antero-dorsal 
  margin 
  is 
  con- 
  

   vex 
  and 
  slightly 
  arched, 
  sloping 
  gradually 
  to 
  the 
  obtusely 
  rounded 
  

   and 
  slightly 
  produced 
  anterior 
  end; 
  ventral 
  margin 
  very 
  broadly 
  and 
  

   evenly 
  curved 
  ; 
  j)osterior 
  end 
  obliquely 
  ascending, 
  obtusely 
  pointed 
  or 
  

   rounded 
  at 
  the 
  tip 
  with 
  a 
  slight 
  dorsal 
  angulation; 
  i^ostero-dorsal 
  mar- 
  

   gin 
  slightly 
  convex, 
  sloping 
  but 
  little, 
  i^inched 
  up 
  into 
  a 
  thin, 
  rather 
  

   prominent 
  keel. 
  The 
  umbos 
  are 
  small 
  and 
  prominent 
  with 
  the 
  beaks 
  

   small, 
  curved 
  inward 
  and 
  backward, 
  closely 
  appressed 
  to 
  the 
  margin. 
  

   The 
  epidermis 
  is 
  grayish 
  or 
  greenish 
  yellow, 
  smooth 
  and 
  shining; 
  the 
  

   surface 
  is 
  brilliantly 
  iridescent, 
  covered 
  with 
  faintly 
  marked, 
  fine, 
  con- 
  

   centric 
  lines, 
  most 
  distinct 
  near 
  the 
  ventral 
  margin 
  and 
  anteriorly; 
  

   under 
  the 
  lens 
  these 
  appear 
  like 
  faint, 
  close 
  undulations 
  over 
  most 
  of 
  

   the 
  surface. 
  Escutcheon 
  defined 
  by 
  a 
  well-marked 
  depression. 
  

  

  The 
  hinge-margin 
  is 
  thickened 
  and 
  forms 
  a 
  very 
  obtuse 
  angle 
  at 
  the 
  

   beaks; 
  the 
  jiosterior 
  portion 
  which 
  is 
  only 
  slightly 
  curved 
  distally 
  is 
  

   longer 
  than 
  the 
  anterior 
  which 
  is 
  nearly 
  straight. 
  In 
  the 
  largest 
  speci- 
  

   mens 
  there 
  are 
  twelve 
  or 
  thirteen 
  acute 
  erect 
  V-shai^ed 
  teeth 
  in 
  each 
  

   series, 
  including 
  one 
  or 
  two 
  minute, 
  proximal 
  ones. 
  The 
  resilial 
  pit 
  is 
  

   minute, 
  situated 
  on 
  the 
  inner 
  face 
  of 
  the 
  thin 
  edentulous 
  hinge-plate, 
  

   beneath 
  the 
  beaks, 
  and 
  faces 
  ventrally 
  so 
  that 
  it 
  is 
  scarcely 
  visible 
  in 
  a 
  

   front 
  view 
  and 
  but 
  j)artially 
  interrupts 
  the 
  hinge-plate. 
  Outside 
  the 
  

   series 
  of 
  teeth, 
  on 
  both 
  sides 
  of 
  the 
  beak 
  there 
  is 
  a 
  smooth, 
  raised 
  

   margin. 
  

  

  Length 
  of 
  one 
  of 
  the 
  larger 
  specimens, 
  7.5 
  mm.; 
  height, 
  5 
  mm.; 
  from 
  

   beak 
  to 
  posterior 
  end, 
  1.5 
  mm. 
  

  

  