﻿876 
  PR0CEEDI2iGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.xx. 
  

  

  Dear 
  the 
  ventral 
  margin 
  these 
  become 
  more 
  elevated, 
  clearly 
  defined, 
  

   and 
  are 
  separated 
  by 
  wider, 
  slightly 
  concave 
  grooves. 
  The 
  hinge-plate 
  

   is 
  rather 
  thin 
  and 
  delicate, 
  regularly 
  curved, 
  without 
  any 
  angle 
  at 
  the 
  

   beaks, 
  with 
  the 
  posterior 
  portion 
  considerably 
  the 
  longer. 
  There 
  is 
  a 
  

   small, 
  median, 
  specialized 
  ligament 
  which 
  occuines 
  a 
  lunate, 
  or 
  nearly 
  

   semicircular 
  notch 
  in 
  the 
  hinge 
  plate 
  directly 
  beneath 
  the 
  beak, 
  which 
  

   does 
  not 
  extend 
  through 
  its 
  entire 
  width 
  although 
  it 
  is 
  here 
  quite 
  nar- 
  

   row. 
  The 
  posterior 
  ligament 
  is 
  pretty 
  well 
  developed 
  and 
  extends 
  

   from 
  the 
  beak, 
  where 
  it 
  is 
  closely 
  connected 
  with 
  the 
  median 
  portion, 
  

   nearly 
  to 
  the 
  distal 
  end 
  of 
  the 
  series 
  of 
  teetb, 
  and 
  occupies 
  a 
  distinct 
  

   marginal 
  groove; 
  the 
  portion 
  nearest 
  the 
  beaks, 
  opposite 
  the 
  smaller 
  

   teeth, 
  is 
  thicker 
  and 
  darker 
  colored 
  than 
  the 
  rest 
  and 
  projects 
  slightly, 
  

   in 
  a 
  dorsal 
  view; 
  a 
  delicate, 
  inconspicuous 
  portion 
  continues 
  a 
  little 
  in 
  

   frontof 
  the 
  beak, 
  in 
  a 
  thin 
  groove. 
  The 
  median 
  portion 
  of 
  the 
  liga- 
  

   ment 
  is 
  so 
  closely 
  connected 
  with 
  the 
  posterior 
  portion 
  that 
  it 
  appears 
  

   to 
  be 
  a 
  specialized, 
  thickened 
  portion 
  of 
  it, 
  but 
  is 
  evidently 
  homologous 
  

   with 
  the 
  resilium 
  of 
  other 
  genera; 
  it 
  is 
  situated, 
  however, 
  outside 
  the 
  

   series 
  of 
  teeth 
  aud 
  must 
  serve 
  as 
  a 
  ligament. 
  The 
  larger 
  teeth 
  are 
  deli- 
  

   cate, 
  subacute, 
  V 
  shape, 
  compressed 
  in 
  a 
  direction 
  parallel 
  Avith 
  the 
  

   dorsal 
  margin, 
  with 
  deep 
  pits 
  between 
  them. 
  There 
  are 
  about 
  ten 
  in 
  

   the 
  anterior 
  series, 
  including 
  three 
  or 
  four, 
  very 
  small, 
  scarcely 
  raised 
  

   ones 
  next 
  the 
  beak 
  ; 
  and 
  fourteen 
  in 
  the 
  posterior 
  series, 
  of 
  which 
  the 
  

   seven 
  distal 
  ones 
  are 
  decidedly 
  larger 
  than 
  the 
  rest, 
  the 
  tenth 
  to 
  the 
  

   thirteenth 
  being 
  the 
  largest; 
  about 
  four, 
  next 
  the 
  j)roximal 
  end 
  of 
  the 
  

   series, 
  are 
  like 
  small, 
  rounded 
  tubercles 
  or 
  granules 
  without 
  a 
  V-shape 
  

   form; 
  following 
  these 
  are 
  three 
  of 
  intermediate 
  form, 
  increasing 
  in 
  size 
  

   distally, 
  the 
  seventh 
  being 
  more 
  or 
  less 
  V-shaped; 
  these 
  smaller 
  teeth 
  

   form 
  a 
  series 
  along 
  the 
  inner 
  edge 
  of 
  the 
  hinge-plate. 
  An 
  edentulous 
  

   ridge, 
  about 
  as 
  long 
  as 
  the 
  space 
  occupied 
  by 
  the 
  lirst 
  three 
  teeth, 
  

   extends 
  from 
  the 
  first 
  tooth 
  to 
  the 
  ligament-pit 
  and 
  is 
  continuous 
  with 
  

   a 
  similar, 
  thinner 
  ridge 
  running 
  below 
  the 
  ligament-pit 
  to 
  the 
  anterior 
  

   series 
  of 
  teeth. 
  The 
  pallial 
  sinus 
  is 
  of 
  moderate 
  size 
  and 
  triangular 
  in 
  

   form. 
  

  

  Length, 
  5 
  mm.; 
  height, 
  4 
  mm. 
  

  

  One 
  live 
  specimen 
  (No. 
  52159), 
  station 
  25G6, 
  oil" 
  Chesapeake 
  Bay, 
  in 
  

   2,620 
  fathoms, 
  1885. 
  

  

  MALLETIA 
  POLITA, 
  new 
  species. 
  

   (Plate 
  LXXXII, 
  lig. 
  10.) 
  

  

  Shell 
  of 
  moderate 
  size, 
  irregularly 
  ovate, 
  somewhat 
  swollen, 
  the 
  ven- 
  

   tral 
  region 
  convex 
  and 
  the 
  posterior 
  end 
  somewhat 
  j^roduced 
  with 
  a 
  

   short 
  rostrum. 
  Epidermis 
  light 
  yellow, 
  lustrous 
  and 
  iridescent. 
  Umbos 
  

   not 
  prominent, 
  beaks 
  small, 
  strongly 
  incurved, 
  only 
  slightly 
  elevated 
  

   above 
  the 
  margin. 
  The 
  antero 
  dorsal 
  margin 
  is 
  slightly 
  convex 
  and 
  

   slopes 
  gently 
  to 
  the 
  short, 
  obtusely 
  rounded 
  anterior 
  end 
  which 
  is 
  

   slightly 
  angulated 
  in 
  the 
  middle; 
  the 
  ventral 
  margin 
  is 
  strongly 
  con- 
  

  

  