﻿Yerrill 
  and 
  Bush 
  — 
  Genera 
  of 
  Ledidce 
  and 
  Nuculidce. 
  63 
  

  

  I. 
  Teeth 
  v-shaped, 
  numerous 
  in 
  both 
  series. 
  

  

  m. 
  Shell 
  oblong 
  or 
  subovate, 
  blunt 
  posteriorly, 
  with 
  a 
  slightly 
  

   sinuous 
  margin, 
  sometimes 
  subrostrate, 
  not 
  carinate. 
  

  

  Yoldiella, 
  nov. 
  

  

  mm. 
  Shell 
  regularly 
  ovate, 
  rounded 
  at 
  both 
  ends, 
  not 
  sinuous, 
  

   nor 
  carinate, 
  (?) 
  no 
  pallial 
  sinus 
  Sarepta 
  A. 
  Ad. 
  

  

  II. 
  Shell 
  short-ovate, 
  not 
  sinuous 
  nor 
  angulated 
  ; 
  teeth 
  few, 
  

  

  oblique, 
  not 
  regularly 
  Y-shaped. 
  Type 
  P. 
  ovatus 
  

  

  Seguenza 
  .. 
  .Phaseolus 
  Seg. 
  

  

  CC. 
  No 
  true 
  internal 
  cartilage 
  ; 
  ligament 
  well-developed, 
  often 
  

  

  prominent 
  behind 
  the 
  beaks. 
  Beaks 
  usually 
  turned 
  

  

  forward. 
  

   D. 
  Siphon 
  tubes 
  and 
  pallial 
  sinus 
  present 
  ; 
  teeth 
  mostly 
  

  

  v-shaped, 
  in 
  two 
  long 
  series, 
  often 
  interrupted 
  by 
  a 
  

  

  median 
  edentulous 
  space 
  Malletinse. 
  

  

  o. 
  Siphon 
  tubes 
  long 
  ; 
  pallial 
  sinus 
  large 
  ; 
  shell 
  elongated, 
  

  

  gaping. 
  

   p. 
  Shell 
  oblong 
  or 
  elliptical, 
  blunt 
  posteriorly, 
  not 
  distinctly 
  

  

  rostrate 
  ; 
  series 
  of 
  teeth 
  unequal 
  ; 
  those 
  in 
  the 
  anterior 
  

  

  series 
  fewer 
  __ 
  Malletia 
  Desm. 
  

  

  pp. 
  Shell 
  long-ovate 
  or 
  oblong, 
  broadly 
  angulated 
  and 
  sinuous 
  

  

  posteriorly 
  ; 
  distinctly 
  rostrate 
  and 
  carinate 
  ; 
  two 
  series 
  

  

  of 
  teeth 
  nearly 
  equal 
  Xeilo 
  H. 
  and 
  A. 
  Ad. 
  

  

  oo. 
  Siphon 
  and 
  pallial 
  sinus 
  small, 
  shell 
  ovate, 
  not 
  gaping 
  ; 
  a 
  

  

  rudimentary 
  marginal 
  resilium 
  Neilonella 
  Dall. 
  

  

  DD. 
  Shell 
  short-ovate 
  or 
  subcordate, 
  closed 
  at 
  both 
  ends 
  ; 
  

  

  umbos 
  prominent 
  ; 
  ligament 
  entirely 
  external 
  ; 
  series 
  of 
  

  

  teeth 
  generally 
  continuous 
  . 
  _ 
  Tindarinse, 
  nov. 
  

  

  s. 
  Shell 
  regularly 
  ovate, 
  grooved, 
  without 
  rostrum 
  or 
  carina 
  ; 
  

  

  beaks 
  turned 
  forward; 
  no 
  pallial 
  sinus. 
  

  

  Tindaria 
  Bellardi. 
  

   6S. 
  Shell 
  ovate, 
  with 
  a 
  distinct 
  posterior 
  sinuosity 
  and 
  a 
  

  

  short 
  rostrum 
  Tindariopsis, 
  no 
  v 
  . 
  

  

  