﻿858 
  rBOCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.xx. 
  

  

  TOLDIA 
  Moller, 
  1842. 
  

  

  Yoldia 
  Verrill 
  aud 
  Bush, 
  Aruei-. 
  Journ. 
  Sci., 
  Ill, 
  pp. 
  5.5, 
  62, 
  figs. 
  12, 
  16, 
  Janu- 
  

   ary, 
  1897. 
  

  

  Type. 
  — 
  Yoldia 
  hyperhorea 
  Torrell= 
  Yoldia 
  arctica 
  Moller 
  (not 
  Gray). 
  

  

  We 
  have 
  restricted 
  this 
  genus 
  to 
  the 
  typical 
  forms, 
  such 
  as 
  Y. 
  lima- 
  

   tula 
  (Say), 
  Y. 
  sapotilla 
  (Gould), 
  Y. 
  myalis 
  (Couthouy), 
  and 
  many 
  closely 
  

   allied 
  foreign 
  species. 
  

  

  These 
  have 
  a 
  nearly 
  smooth, 
  compressed, 
  lanceolate, 
  gaping 
  shell, 
  

   more 
  or 
  less 
  prolonged 
  and 
  tapered 
  posteriorly, 
  with 
  a 
  poorly 
  defined, 
  

   wide 
  rostrum, 
  generally 
  without 
  carinations. 
  The 
  external 
  ligament 
  is 
  

   marginal, 
  feebly 
  developed, 
  continuous 
  under 
  the 
  beaks, 
  and 
  not 
  much 
  

   differentiated 
  from 
  the 
  general 
  epidermis. 
  The 
  choudrophore 
  is 
  large, 
  

   concave, 
  and 
  projects 
  within 
  the 
  margin. 
  The 
  pallial 
  sinus 
  is 
  large 
  

   and 
  deep. 
  The 
  siphon 
  tubes 
  and 
  posterior 
  pallial 
  tentacle 
  are 
  long. 
  

   The 
  palpal 
  tentacles 
  are 
  long 
  and 
  tapered; 
  in 
  life 
  they 
  may 
  extend 
  

   nearly 
  to 
  the 
  end 
  of 
  the 
  expanded 
  siphon. 
  

  

  ADRANELLA, 
  new 
  subgenus 
  of 
  Yoldia. 
  

  

  Type. 
  — 
  Adranella 
  casta, 
  new 
  species. 
  

  

  This 
  subgenus 
  is 
  allied 
  to 
  Yoldia, 
  but 
  is 
  distinguished 
  by 
  its 
  oblong- 
  

   ovate, 
  compressed 
  form, 
  with 
  a 
  broadly 
  rounded, 
  posterior 
  end, 
  having 
  

   a 
  very 
  small, 
  nearly 
  obsolete, 
  rostrum. 
  Surface 
  sculi)tured 
  with 
  dis- 
  

   tinct, 
  raised, 
  concentric 
  lines. 
  Hinge-plate 
  and 
  teeth 
  strong. 
  Eesilium 
  

   occupying 
  a 
  distinct 
  pit 
  in 
  the 
  apex 
  of 
  a 
  large 
  shelf-like, 
  triangular 
  

   chondrophore. 
  

  

  YOLDIA 
  (ADRANELLA) 
  CASTA, 
  new 
  species. 
  

  

  (Plate 
  LXXX, 
  fig. 
  4.) 
  

  

  Shell 
  small, 
  oblong-ovate, 
  somewhat 
  compressed, 
  inequilateral, 
  with 
  

   the 
  posterior 
  end 
  a 
  little 
  the 
  longer 
  and 
  considerably 
  the 
  broader. 
  

   Umbos 
  small; 
  beaks 
  curved 
  inward 
  and 
  slightly 
  backward. 
  Antero- 
  

   dorsal 
  margin 
  slightly 
  concave 
  near 
  the 
  beak, 
  a 
  little 
  convex 
  opposite 
  

   the 
  distal 
  teeth; 
  anterior 
  end 
  a 
  little 
  narrowed, 
  obtusely 
  rounded; 
  

   ventral 
  margin 
  broadly 
  and 
  evenly 
  rounded 
  with 
  a 
  very 
  faint 
  undu- 
  

   lation 
  posteriorly; 
  postero-dorsal 
  margin 
  a 
  little 
  convex, 
  sloping 
  less 
  

   than 
  the 
  anterior, 
  and 
  turning 
  up 
  at 
  the 
  end 
  so 
  as 
  to 
  form 
  a 
  slight, 
  

   hardly 
  distinct 
  rostrum. 
  The 
  hinge-plate 
  is 
  rather 
  large 
  aud 
  thick, 
  

   especially 
  distally 
  on 
  each 
  side, 
  becoming 
  narrow 
  and 
  turning 
  upward 
  

   at 
  the 
  beak, 
  where 
  it 
  is 
  interrupted 
  . 
  by 
  a 
  small, 
  rather 
  deep 
  resilial 
  

   pit, 
  which 
  is 
  bordered 
  interiorly 
  by 
  a 
  thickened 
  extension 
  of 
  the 
  hinge- 
  

   margin 
  forming 
  a 
  sort 
  of 
  shelf, 
  the 
  whole 
  constituting 
  a 
  broadly 
  trian- 
  

   gular 
  chondrophore 
  with 
  the 
  pit 
  near 
  its 
  apex. 
  The 
  anterior 
  series 
  of 
  

   teeth 
  contains 
  twelve, 
  of 
  which 
  three 
  or 
  four 
  proximal 
  ones 
  are 
  very 
  

   small, 
  and 
  form 
  a 
  series 
  which 
  curves 
  upward, 
  exterior 
  to 
  the 
  chondro- 
  

   phore, 
  and 
  terminates 
  at 
  the 
  superior 
  margin 
  of 
  the 
  shell; 
  the 
  teeth 
  

  

  