﻿54 
  Verrill 
  and 
  Bush 
  — 
  Genera 
  of 
  Ledidm 
  and 
  JVueulidce. 
  

  

  Family 
  Ledidje. 
  Subfamily 
  Ledin^e. 
  

   Leda 
  Schumacher, 
  1817. 
  Figure 
  19. 
  Type 
  Z. 
  rostrata 
  (Mont.). 
  

  

  This 
  genus 
  has 
  been 
  variously 
  extended 
  and 
  restricted 
  by 
  

   authors, 
  and 
  several 
  subgeneric 
  and 
  sectional 
  groups 
  have 
  been 
  

   proposed. 
  In 
  the 
  more 
  extended 
  sense 
  it 
  is 
  scarcely 
  capable 
  of 
  a 
  

   definition 
  that 
  will 
  distinguish 
  it 
  from 
  Yoldia, 
  etc. 
  

  

  We 
  propose, 
  therefore, 
  to 
  restrict 
  it 
  to 
  the 
  typical 
  species, 
  such 
  

   as 
  L. 
  cuspidata 
  Gld., 
  caudata 
  Donovan 
  (fig. 
  19), 
  pernula 
  (Mull.), 
  

   tenuisulcata 
  (Couth.) 
  and 
  many 
  others, 
  closely 
  related. 
  These 
  have 
  

   a 
  long, 
  tapered, 
  bicarinate 
  rostrum, 
  and 
  well-developed 
  siphon 
  

   tubes, 
  partially 
  united. 
  The 
  palpal 
  tentacles 
  are 
  long, 
  flat, 
  

   tapered, 
  and 
  arise 
  external 
  to 
  the 
  bases 
  of 
  the 
  outer 
  palpi, 
  

   which 
  are 
  broad, 
  with 
  slender, 
  acute 
  posterior 
  tips. 
  

  

  Ledella, 
  gen. 
  nov. 
  Figures 
  13, 
  18. 
  Type 
  X. 
  Messanensis 
  (Seg.). 
  

  

  Junonia 
  Seguenza, 
  Nuculidi 
  terziarie 
  merid. 
  d' 
  Ital., 
  R. 
  Accad. 
  

   Lincei, 
  i, 
  p. 
  1175, 
  1877 
  (not 
  of 
  Hiibner). 
  

  

  This 
  group 
  includes 
  a 
  large 
  number 
  of 
  small 
  species, 
  both 
  living 
  

   and 
  fossil, 
  in 
  which 
  the 
  shell 
  is 
  rather 
  short, 
  usually 
  ovate 
  or 
  

   swollen, 
  with 
  a 
  small, 
  acute, 
  or 
  subacute, 
  uuicarinate 
  rostrum, 
  situ- 
  

   ated 
  medially 
  or 
  submedially, 
  and 
  defined 
  below 
  by 
  an 
  emargina- 
  

   tion 
  or 
  undulation 
  in 
  the 
  postero-ventral 
  margin. 
  The 
  postero- 
  

   dorsal 
  margin 
  is 
  usually 
  convex. 
  The 
  escutcheon 
  or 
  ligamental 
  

   area 
  is 
  distinctly 
  defined 
  by 
  the 
  carina, 
  but 
  is 
  not 
  sunken. 
  The 
  

   chondrophore 
  is 
  usually 
  small 
  but 
  distinct. 
  The 
  siphon 
  tubes 
  are 
  

   separate, 
  at 
  least 
  in 
  some 
  species. 
  

  

  The 
  following 
  species 
  appear 
  to 
  belong 
  here 
  : 
  

  

  L. 
  seminula 
  (Seg.), 
  L. 
  Messanensis 
  (Seg.) 
  (fig. 
  13), 
  L. 
  JVicotrce 
  

   (Seg.), 
  L. 
  peraffinis 
  (Seg.), 
  L. 
  rectldorsata 
  (Seg.), 
  L. 
  confusa 
  

   (Seg.), 
  L. 
  sulidula 
  Smith, 
  L. 
  semen 
  Smith, 
  L. 
  confinis 
  Smith, 
  

   L. 
  inopinata 
  Smith, 
  L. 
  prolata 
  Smith, 
  L. 
  -ultima 
  Smith, 
  and 
  L. 
  

   parva 
  V. 
  & 
  B.* 
  

  

  Portlandia 
  Morch. 
  Type 
  P. 
  arctica 
  (Gray), 
  \%\§=:Leda 
  Port- 
  

   landica 
  (Hitch.). 
  

  

  We 
  consider 
  this 
  a 
  distinct 
  genus, 
  but 
  w 
  T 
  ould 
  restrict 
  it 
  to 
  the 
  

   original 
  type. 
  In 
  many 
  respects 
  this 
  genus 
  is 
  intermediate 
  

   between 
  Leda 
  and 
  Yoldia. 
  In 
  its 
  closed 
  shell, 
  definite 
  rostrum, 
  

  

  * 
  Ledella 
  parva, 
  sp. 
  ndv. 
  Figure 
  18. 
  

  

  Shell 
  minute, 
  smooth, 
  narrow 
  ovate, 
  inequilateral, 
  obtusely 
  rounded 
  anteriorly, 
  

   slightly 
  rostrate 
  posteriorly 
  with 
  a 
  slight 
  postero-ventral 
  emargination 
  ; 
  the 
  short 
  

   rostrum 
  subtruncate 
  at 
  tip 
  and 
  defined 
  by 
  an 
  inconspicuous 
  ridge. 
  Umbos 
  some- 
  

   what 
  swollen, 
  beaks 
  a 
  little 
  prominent 
  and 
  turned 
  slightly 
  backward. 
  Hinge- 
  

   plate 
  strong 
  with 
  fifteen 
  anterior 
  and 
  nine 
  posterior 
  teeth. 
  Chondrophore 
  rather 
  

   small, 
  triangular 
  with 
  a 
  distinctly 
  projecting 
  inner 
  margin. 
  Length, 
  3 
  mm 
  ; 
  

   height, 
  2'" 
  m 
  . 
  

  

  Station 
  2689, 
  off 
  Martha's 
  Vineyard, 
  in 
  525 
  fathoms, 
  1886. 
  

  

  