﻿884 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol. 
  xx. 
  

  

  This 
  division 
  was 
  proi)osed 
  for 
  those 
  species 
  Avhich 
  have 
  a 
  short 
  ros- 
  

   trum, 
  defined 
  by 
  a 
  radial 
  ridge 
  and 
  a 
  furrow. 
  The 
  type 
  has 
  a 
  well- 
  

   marked 
  dorsal 
  ligamental 
  furrow 
  and 
  a 
  small 
  notch 
  or 
  "socket" 
  under 
  

   the 
  beak 
  for 
  the 
  specialized 
  part 
  of 
  the 
  ligament. 
  It 
  is 
  uncertain 
  

   whether 
  it 
  has 
  a 
  siphon 
  and 
  a 
  pallial 
  sinus. 
  In 
  case 
  these 
  are 
  present^ 
  

   it 
  should 
  form 
  a 
  distinct 
  geuus 
  and 
  be 
  placed 
  under 
  Malletiua^ 
  

  

  ANALYTICAL 
  TABLK 
  OF 
  KECEXT 
  SUBFAMILIES, 
  GENEKA, 
  AND 
  SUBGENERA 
  OF 
  LEDID.E 
  

   AND 
  NUCULID.E 
  HERE 
  ADOPTED. 
  

  

  A. 
  Shell 
  not 
  gaping, 
  short-ovate, 
  subtrigoual, 
  or 
  rounded; 
  posterior 
  end 
  without 
  a 
  

   rostrum; 
  beaks 
  usually 
  curved 
  backward; 
  uo 
  sii)lion 
  tubes 
  nor 
  pallial 
  sinus. 
  

  

  NucuUidw 
  d'Orbigiiy. 
  

  

  B. 
  Shell 
  more 
  or 
  less 
  trigonal, 
  usnallj' 
  oblique; 
  posterior 
  end 
  usually 
  shorter; 
  

  

  beaks 
  turned 
  backward 
  NiicuUnw 
  Verrill 
  and 
  Bush. 
  

  

  c. 
  Teeth 
  numerous, 
  transverse, 
  V-sluipcd, 
  forming 
  two 
  convexly 
  arched 
  or 
  angu- 
  

  

  lated 
  series; 
  a 
  distinct 
  median 
  chondrojihore; 
  no 
  lateral 
  teeth. 
  

  

  Nuciila 
  Lamarck. 
  

   cc. 
  Teeth 
  few, 
  not 
  forming 
  long 
  series; 
  a 
  long 
  lateral 
  tooth 
  in 
  each 
  valve; 
  no 
  

  

  median 
  chondrophore 
  Nuculina 
  d'Orbigny 
  

  

  A 
  A. 
  Shell 
  ovate, 
  oblong 
  or 
  lanceolate; 
  posterior 
  end 
  generally 
  the 
  longer 
  and 
  

   usually 
  more 
  or 
  les.s 
  rostrated; 
  siphon 
  tubes 
  and 
  pallial 
  sinus 
  generally 
  present. 
  

  

  Lcdidii' 
  H. 
  and 
  A. 
  Adams. 
  

  

  C. 
  Cartilage 
  or 
  resilium 
  present, 
  not 
  closely 
  united 
  with 
  the 
  external 
  ligament. 
  

  

  Ledina: 
  H. 
  and 
  A. 
  Adams. 
  

   a. 
  Eesiliuni 
  supported 
  by 
  a 
  definite 
  concave 
  chondropliore 
  extending 
  inward 
  to,. 
  

  

  or 
  beyond, 
  the 
  inner 
  edge 
  of 
  the 
  hinge-plate. 
  

   h. 
  Shell 
  not 
  ga])ing 
  unless 
  at 
  the 
  end 
  of 
  the 
  rostrum. 
  

  

  c. 
  Shell 
  distinctly 
  rostrated 
  and 
  carinated 
  posteriorly, 
  

  

  Leda 
  Schumacher 
  (sense 
  extended). 
  

  

  d. 
  Shell 
  elongated 
  and 
  taj)ered 
  posteriorly, 
  rostrum 
  long, 
  bicariuate, 
  blunt 
  ; 
  liga- 
  

   mental 
  area 
  or 
  escutcheon 
  long 
  and 
  well-detined; 
  pallial 
  sinus 
  and 
  .siphon 
  

   tubes 
  developed 
  Leda 
  (sense 
  restricted). 
  

  

  dd. 
  Shell 
  shorter, 
  swollen, 
  ovate 
  or 
  oblong, 
  posteriorly 
  not 
  much 
  elongated; 
  ros- 
  

   trum 
  short, 
  usually 
  acute, 
  unicarinate. 
  

  

  e. 
  Shell 
  ovate, 
  rostrum 
  small, 
  acute; 
  ligamental 
  area 
  or 
  escutcheon 
  distinctly 
  

   bordered 
  by 
  a 
  carin.-i. 
  

  

  /". 
  Rostrum 
  short, 
  subacute, 
  submedian, 
  defined 
  below 
  by 
  a 
  ventral 
  sinuosity 
  or 
  

   emargination 
  Jnnonhi 
  Seguenzai=Z.er?e?/rt 
  Verrill 
  and 
  Bush. 
  

  

  ff. 
  Rostrum 
  short, 
  dorsal, 
  not 
  defined 
  below 
  by 
  a 
  ventral 
  sinuosity; 
  postero- 
  

   dorsal 
  margin 
  concave 
  ; 
  escutcheon 
  -sunken 
  Jitpiteria 
  Bellardi. 
  

  

  ce. 
  Shell 
  oblong, 
  angular, 
  subtruncate, 
  rostrum 
  short, 
  angular, 
  dorsal, 
  defined 
  

   below 
  by 
  a 
  marginal 
  sinuosity; 
  escutcheon 
  well-defined 
  Portlandia 
  Morch. 
  

  

  cct:. 
  Shell 
  not 
  rostrated, 
  small, 
  ovate 
  or 
  elliptical, 
  rounded 
  at 
  both 
  ends, 
  anterior 
  

   end 
  the 
  shorter, 
  no 
  carina, 
  luuule, 
  nor 
  escutcheon 
  ; 
  cartilage 
  posterior, 
  inter- 
  

   nymphal 
  Microyoldia 
  Verrill 
  and 
  Bush. 
  

  

  hb. 
  Shell 
  oblong 
  or 
  lanceolate, 
  compressed, 
  nearly 
  plain, 
  more 
  or 
  less 
  gaping 
  at 
  

   both 
  ends; 
  rostrum 
  not 
  well-detined; 
  pallial 
  sinus 
  large 
  and 
  broad; 
  tubes 
  loug, 
  

   united. 
  

  

  [/. 
  Teeth 
  transverse, 
  -sha])ed, 
  numerous, 
  in 
  two 
  long 
  series 
  ; 
  chondrophore 
  large,, 
  

   concave, 
  projecting 
  strongly 
  inside 
  the 
  hinge-plate. 
  

  

  Toldia 
  Midler 
  (sense 
  extended). 
  

  

  k. 
  Shell 
  large, 
  compressed, 
  rounded 
  anteriorly, 
  broadest 
  posteriorly 
  witli 
  aposfero- 
  

   ventral 
  protrusiou 
  and 
  radial 
  ridge; 
  rostrum 
  short, 
  broad, 
  ]>oorly 
  defined; 
  

   external 
  ligauieut 
  well 
  developed, 
  i)rominent 
  both 
  sides 
  of 
  the 
  b(>aks, 
  occu- 
  

   pying 
  a 
  continuous 
  furrow; 
  no 
  lunule 
  nor 
  escutcheon. 
  

  

  Megayohlia 
  Verrill 
  and 
  Bush. 
  

  

  