﻿56 
  Verrill 
  and 
  Bush 
  — 
  Genera 
  of 
  Zedidce 
  and 
  NuculidcB. 
  

  

  which 
  feebly 
  defines 
  an 
  obscure, 
  blunt, 
  rostral 
  region, 
  without 
  

   any 
  definite 
  carination. 
  The 
  shells 
  do 
  not 
  gap, 
  but 
  close 
  tightly, 
  

   except 
  that 
  at 
  the 
  rostral 
  angle 
  of 
  some 
  species 
  there 
  may 
  be 
  a 
  

   slight 
  divergence. 
  The 
  internal 
  cartilage, 
  which 
  is 
  often 
  rela- 
  

   tively 
  large, 
  occupies 
  a 
  simple 
  notch, 
  which 
  interrupts 
  the 
  hinge 
  

   margin 
  more 
  or 
  less 
  completely 
  and 
  generally 
  shows 
  externally 
  

   in 
  a 
  dorsal 
  view 
  ; 
  the 
  notch 
  usually 
  terminates 
  within 
  on 
  the 
  

   inner 
  or 
  inferior 
  surface 
  of 
  the 
  hinge 
  plate 
  and 
  is 
  often 
  bounded 
  

   within 
  by 
  a 
  slight 
  ridge. 
  A 
  weak 
  external 
  ligament 
  is 
  p7*esent 
  

   on 
  the 
  postero-dorsal 
  margin. 
  A 
  relatively 
  small, 
  pallial 
  sinus 
  

   has 
  been 
  observed 
  in 
  several 
  of 
  the 
  species, 
  but 
  is 
  usually 
  indis- 
  

   tinct. 
  The 
  siphon 
  tubes, 
  as 
  observed 
  in 
  a 
  few 
  of 
  the 
  species, 
  are 
  

   slender 
  and 
  united 
  for 
  more 
  than 
  half 
  their 
  length. 
  

  

  The 
  following 
  are 
  some 
  of 
  the 
  species 
  : 
  

  

  Y. 
  lucida 
  (Loven), 
  Y 
  inflata 
  V. 
  & 
  B.,* 
  Y. 
  Jeffreysi 
  (Hidalgo), 
  

   Y. 
  lenticula 
  (Moller), 
  Y. 
  frigida 
  (Torell),and 
  Y. 
  Iloylei 
  (Smith). 
  

  

  Microyoldia, 
  gen. 
  nov. 
  Figures 
  5, 
  6. 
  Type 
  M. 
  regidaris 
  (V.).f 
  

  

  Shell 
  small, 
  tightly 
  closed, 
  veneriforra, 
  with 
  the 
  anterior 
  end 
  

   the 
  shorter, 
  with 
  the 
  beaks 
  turned 
  forward. 
  A 
  posterior 
  mar- 
  

   ginal 
  ligament 
  in 
  a 
  distinct 
  groove, 
  continued 
  under 
  the 
  beaks. 
  

   Hinge-plate 
  and 
  teeth 
  rather 
  strong 
  ; 
  anterior 
  series 
  of 
  teeth 
  the 
  

   shorter, 
  forming 
  a 
  marked 
  angle 
  with 
  the 
  posterior 
  series. 
  Internal 
  

   cartilage 
  supported 
  by 
  a 
  relatively 
  large 
  and 
  strong 
  chondrophore, 
  

   placed 
  on 
  the 
  suriace 
  of 
  the 
  hinge-plate, 
  distinctly 
  behind 
  the 
  

   beaks 
  and 
  at 
  the 
  proximal 
  end 
  of 
  the 
  posterior 
  series 
  of 
  teeth. 
  

   Pallial 
  line 
  indistinct. 
  

  

  The 
  curious 
  little 
  shell 
  for 
  which 
  this 
  genus 
  is 
  proposed 
  is 
  

   remarkable 
  for 
  its 
  form 
  and 
  the 
  internymphal 
  position 
  of 
  the 
  carti- 
  

   lage 
  and 
  chrondrophore, 
  as 
  well 
  as 
  for 
  its 
  few 
  short 
  teeth. 
  If 
  we 
  

   are 
  correct 
  in 
  our 
  conclusions 
  as 
  to 
  the 
  anterior 
  and 
  posterior 
  ends, 
  

   the 
  beaks 
  turn 
  forward 
  as 
  in 
  Tindaria. 
  

  

  Subfamily 
  Malletin^e. 
  

  

  Malletia 
  Desmoulins 
  (restricted). 
  Figure 
  9. 
  Type 
  Malletia 
  

   Chile?isis 
  Desmoulins. 
  

  

  We 
  propose 
  to 
  restrict 
  this 
  genus 
  to 
  those 
  species 
  having 
  a 
  

   nearly 
  smooth, 
  somewhat 
  compressed, 
  oblong 
  or 
  elliptical 
  shell, 
  

  

  * 
  Yoldiella 
  inflata, 
  sp. 
  nov. 
  Figures 
  3, 
  4, 
  11. 
  

  

  Shell 
  small, 
  smooth, 
  shining, 
  somewhat 
  iridescent, 
  swollen, 
  rather 
  short, 
  sub- 
  

   ovate, 
  inequilateral, 
  broadly 
  rounded 
  anteriorly, 
  broad 
  and 
  obtusely 
  subtrun- 
  

   cated 
  posteriorly, 
  with 
  a 
  slight 
  angle 
  at 
  the 
  upper 
  extremity. 
  Umbos 
  well- 
  

   rounded; 
  beaks 
  small, 
  appressed 
  to 
  the 
  margin. 
  External 
  ligament 
  delicate. 
  

   HiDge-plate 
  moderately 
  broad, 
  with 
  nine 
  to 
  eleven 
  anterior 
  and 
  about 
  ten 
  

   posterior 
  teeth, 
  separated 
  by 
  the 
  small 
  cartilage 
  pit. 
  Epidermis 
  pale 
  olive-yellow 
  

   or 
  straw 
  color. 
  

  

  Length 
  of 
  one 
  of 
  the 
  largest 
  specimens, 
  6 
  mm 
  ; 
  height, 
  4-5 
  mm 
  ; 
  thickness, 
  about 
  

   3 
  mm 
  . 
  

  

  Found 
  at 
  about 
  twenty 
  stations 
  from 
  south 
  of 
  Georges' 
  Bank 
  to 
  Cape 
  Hatteras. 
  

   N. 
  C, 
  in 
  516 
  to 
  1608 
  fathoms, 
  1883-1886. 
  

  

  f 
  Verrill, 
  Trans. 
  Conn. 
  Acad., 
  vi, 
  p. 
  228, 
  1884. 
  

  

  