﻿NO. 
  1139. 
  DEEP-WATEB 
  MOLLUSC 
  A— 
  VEEBILL 
  AND 
  BUSH. 
  865 
  

  

  just 
  beneath 
  the 
  beak, 
  forms 
  a 
  notch 
  which 
  completely 
  interrupts 
  the 
  

   hinge-margin. 
  

  

  Length 
  of 
  one 
  of 
  the 
  largest 
  specimens, 
  6 
  mm.; 
  height, 
  4.5 
  mm., 
  

   thickness, 
  3 
  mm. 
  ; 
  from 
  beak 
  to 
  posterior 
  angle, 
  4 
  mm. 
  

  

  Found 
  in 
  considerable 
  numbers, 
  at 
  about 
  twenty 
  stations, 
  between 
  K. 
  

   lat. 
  41° 
  53', 
  W. 
  long. 
  65° 
  35', 
  and 
  K 
  lat. 
  35° 
  9' 
  50", 
  W. 
  long. 
  74° 
  57' 
  40", 
  

   in 
  516 
  to 
  1,608 
  fathoms, 
  1883-1886. 
  Several 
  live 
  specimens, 
  at 
  station 
  

   2079, 
  in 
  75 
  fathoms. 
  

  

  This 
  species 
  is 
  closely 
  related 
  to 
  Y. 
  lucida 
  (Loven), 
  from 
  which 
  it 
  is 
  

   easily 
  separated 
  by 
  its 
  shorter, 
  broader, 
  more 
  swollen 
  form, 
  its 
  strongly 
  

   curved 
  ventral 
  margin, 
  and 
  very 
  distinct 
  postero- 
  dorsal 
  angle. 
  It 
  is 
  

   shorter 
  and 
  has 
  a 
  broader 
  posterior 
  end 
  than 
  most 
  of 
  the 
  related 
  

   sjjecies. 
  The 
  resilium 
  is 
  not 
  visible 
  externally. 
  

  

  YOLDIELLA 
  SUBANGULATA, 
  new 
  species. 
  

   (Plates 
  LXXVII, 
  fig. 
  3; 
  LXXIX, 
  fig, 
  6.) 
  

  

  Very 
  similar 
  to 
  the 
  preceding 
  species 
  in 
  form 
  bnt 
  less 
  pointed 
  pos- 
  

   teriorly 
  and 
  larger. 
  The 
  umbos 
  are 
  small, 
  not 
  prominent; 
  beaks 
  are 
  

   small, 
  directly 
  incurved, 
  appressed 
  to 
  the 
  hinge-margin 
  but 
  not 
  dis- 
  

   tinctly 
  notched 
  by 
  the 
  resilial 
  pit. 
  The 
  antero-dorsal 
  margin 
  is 
  convex, 
  

   arched; 
  the 
  anterior 
  end 
  is 
  a 
  little 
  produced, 
  obtusely 
  rounded; 
  ven- 
  

   tral 
  margin 
  evenly 
  and 
  broadly 
  rounded, 
  slightly 
  produced 
  posteriorly, 
  

   forming 
  an 
  obscure 
  obtuse 
  angle 
  as 
  it 
  merges 
  into 
  the 
  posterior 
  end 
  

   which 
  is 
  obliquely 
  subtruncated 
  or 
  a 
  little 
  inflexed 
  in 
  the 
  middle, 
  with 
  

   a 
  i^rominent 
  dorsal 
  angle; 
  the 
  postero-dorsal 
  margin 
  slopes 
  but 
  little, 
  

   and 
  is 
  nearly 
  straight, 
  with 
  the 
  compressed 
  edges 
  forming 
  a 
  slight 
  keel, 
  

   which 
  is 
  a 
  little 
  convex 
  in 
  the 
  middle. 
  A 
  well 
  marked 
  ridge 
  runs 
  to 
  

   the 
  postero-dorsal 
  angle, 
  and 
  a 
  less 
  distinct 
  one 
  to 
  the 
  postero-ventral 
  

   angle; 
  between 
  these 
  there 
  is 
  a 
  slight 
  depression 
  of 
  the 
  surface. 
  Sur- 
  

   face 
  nearly 
  smooth, 
  lustrous, 
  reflecting 
  prismatic 
  colors, 
  and 
  covered 
  

   with 
  faint 
  lines 
  of 
  growth 
  and 
  a 
  few 
  inconspicuous 
  irregular 
  sulci; 
  

   epidermis 
  pale 
  olive 
  yellow. 
  The 
  hinge-margin 
  is 
  narrow, 
  very 
  obtusely 
  

   angled, 
  and 
  is 
  interrupted 
  under 
  the 
  beaks 
  by 
  the 
  small 
  notch-like 
  

   resilial 
  pit. 
  The 
  anterior 
  series 
  of 
  teeth 
  is 
  slightly 
  arched 
  and 
  con- 
  

   tains 
  about 
  seventeen 
  teeth, 
  including 
  three 
  or 
  four 
  minute 
  proximal 
  

   ones; 
  the 
  larger 
  ones 
  are 
  high 
  and 
  sharp. 
  The 
  posterior 
  series 
  is 
  a 
  

   little 
  longer 
  and 
  contains 
  about 
  eighteen, 
  similar, 
  but 
  somewhat 
  more 
  

   slender 
  teeth. 
  A 
  thin, 
  smooth 
  margin 
  extends 
  along 
  outside 
  both 
  series. 
  

   There 
  is 
  a 
  small 
  internal 
  denticle 
  at 
  the 
  front 
  edge 
  of 
  the 
  resilial 
  pit. 
  

   Pallial 
  sinus 
  narrow, 
  considerably 
  inflexed. 
  

  

  Length, 
  8 
  mm. 
  ; 
  height, 
  5 
  mm. 
  ; 
  thickness, 
  about 
  4 
  mm. 
  ; 
  from 
  beak 
  to 
  

   anterior 
  end, 
  3 
  mm. 
  ; 
  posterior 
  end, 
  5 
  mm. 
  

  

  One 
  live 
  specimen 
  was 
  dredged 
  by 
  the 
  Baclie 
  at 
  station 
  46, 
  IT. 
  lat. 
  

   43° 
  3'; 
  W. 
  long. 
  70O 
  4', 
  in 
  51 
  fathoms, 
  1874. 
  

   Proc. 
  N. 
  M. 
  vol. 
  XX 
  55 
  

  

  