﻿NO. 
  1139. 
  BEEP-WATER 
  MOLLUSCA—TERRILL 
  AND 
  BUSH. 
  833 
  

  

  pectin 
  idial 
  teeth 
  obsolete. 
  The 
  shell 
  has 
  a 
  prismatic 
  structure. 
  Inter- 
  

   nal 
  lira; 
  and 
  auricular 
  crurie 
  well 
  -developed. 
  

  

  The 
  structure 
  of 
  the 
  animal 
  was 
  described 
  by 
  Mr. 
  Dall 
  as 
  very 
  dif- 
  

   ferent 
  from 
  that 
  of 
  typical 
  Amnsium. 
  According 
  to 
  liis 
  description 
  it 
  

   has 
  a 
  single 
  pair 
  of 
  gills, 
  with 
  long, 
  simple, 
  separate 
  filaments. 
  The 
  

   foot 
  is 
  slender, 
  with 
  a 
  byssal 
  groove 
  ; 
  the 
  end 
  is 
  much 
  enlarged, 
  with 
  

   an 
  oblicpie, 
  expanded, 
  concave 
  terminal 
  disk, 
  striated 
  within. 
  No 
  

   labial 
  palpi. 
  Ocelli 
  without 
  pigment. 
  

  

  A 
  specimen, 
  well 
  preserved 
  in 
  alcohol, 
  examined 
  by 
  us, 
  had 
  two 
  rows 
  

   of 
  long, 
  slender, 
  reliected 
  gill-filaments, 
  as 
  usual 
  in 
  this 
  family. 
  They 
  

   were 
  attached 
  to 
  a 
  broad 
  basal 
  membrane, 
  with 
  a 
  free, 
  lanceolate, 
  pos- 
  

   terior 
  portion. 
  Two 
  pairs 
  of 
  broad, 
  foliaceous, 
  incurved 
  palpi, 
  tinged 
  

   with 
  dark 
  brown. 
  Those 
  of 
  the 
  anterior 
  pair 
  are 
  united 
  into 
  a 
  hood 
  

   over 
  the 
  mouth; 
  the 
  others 
  are 
  smaller, 
  curved 
  inward, 
  somewhat 
  lau- 
  

   ceolate 
  at 
  the 
  tips. 
  No 
  ocelli 
  could 
  be 
  found. 
  The 
  pallial 
  tentacles 
  are 
  

   all 
  in 
  one 
  row, 
  numerous, 
  of 
  various 
  sizes; 
  from 
  four 
  to 
  six 
  large 
  ernes, 
  

   with 
  as 
  many 
  alternating 
  small 
  ones, 
  correspond 
  to 
  each 
  hirger 
  undu- 
  

   lation 
  or 
  scallop 
  of 
  the 
  mantle-margin. 
  No 
  guard-tentacles. 
  Muscular 
  

   pallial 
  border 
  is 
  broad, 
  thickened, 
  radially 
  striated, 
  forming 
  a 
  ridge, 
  

   as 
  preserved, 
  but 
  not 
  tentaculated. 
  Free 
  portion 
  of 
  rectum 
  long 
  and 
  

   slender. 
  

  

  A 
  synopsis 
  of 
  the 
  Pectiuidfe 
  was 
  recently 
  published 
  by 
  Dr. 
  Frederic© 
  

   Sacco.' 
  

  

  He 
  recognized 
  three 
  genera 
  : 
  Ghlamijs, 
  Amusmuni, 
  and 
  Peeten, 
  with 
  the 
  

   same 
  types 
  given 
  by 
  Yerrill. 
  Under 
  (Jhlamys 
  he 
  gives 
  nine 
  subgenera. 
  

   Of 
  these, 
  four 
  — 
  Chlamys 
  (restricted), 
  Trinnites, 
  ^J^quipecten, 
  and 
  Fallio- 
  

   Imn 
  — 
  correspond 
  with 
  the 
  groups 
  of 
  the 
  same 
  name 
  given 
  by 
  Verrill; 
  

   Fellpes 
  Locard 
  (type, 
  pesfelis 
  L.), 
  Peplum 
  Buccpioy, 
  Dantzenberg, 
  and 
  

   Dollfus, 
  1889 
  (type, 
  Inflexum 
  Poll), 
  Macroehalmts 
  Sacco, 
  18!»7 
  (type, 
  Jatis- 
  

   sima 
  Brocchi), 
  Flexopecten 
  Sacco, 
  1897 
  {ty^ie^flexnosus 
  Poll), 
  Lissochlamis 
  

   Sacco, 
  1897 
  (type, 
  excisa 
  Bronn), 
  are 
  additional 
  to 
  those 
  given 
  by 
  Yerrill. 
  

  

  Under 
  Amussium 
  he 
  has, 
  besides 
  the 
  typical 
  group, 
  four 
  subgenera. 
  

   Of 
  these, 
  two 
  are 
  new 
  — 
  Parramussium 
  Sacco, 
  1897 
  (type, 
  (hiodecimlamel- 
  

   hitum 
  Broiiu), 
  Variamnssium 
  Sacco, 
  1897 
  (type, 
  cancellatum 
  Schmidt). 
  

   The 
  two 
  others 
  are 
  Fropeamussmm 
  aud 
  Psendamussinm. 
  

  

  The 
  three 
  new 
  subgenera 
  of 
  I'ecten 
  are 
  Amussiopecten 
  Sacco, 
  1897 
  

   {ty 
  \)e, 
  burdigalensis 
  Lamarck); 
  Oiipecten 
  Sacco, 
  1897 
  (type, 
  rottmdatus 
  

   Lamarck); 
  and 
  Flabellipecten 
  Sacco, 
  1897 
  {ty\)Q^ 
  JiaheUiformis 
  Brocchi). 
  

  

  • 
  Bolletino 
  del 
  Mus. 
  Zool. 
  ed 
  Anat. 
  Comp., 
  Univ. 
  di 
  Torino, 
  XII, 
  p. 
  101. 
  It 
  was 
  

   apparently 
  issued 
  at 
  about 
  the 
  same 
  time 
  aw 
  that 
  by 
  Professor 
  Verrill, 
  here 
  

   abstracted. 
  

  

  Proc. 
  N. 
  M. 
  vol. 
  XX 
  53 
  

  

  