﻿224 
  rKOCEEDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIETY. 
  

  

  Though 
  Lucinopsis 
  is 
  closely 
  related 
  to 
  Lajonlcairea, 
  the 
  separated 
  

   siphons, 
  their 
  great 
  length, 
  and 
  the 
  correspondingly 
  long 
  ascending 
  

   pallial 
  sinus 
  seem 
  to 
  prevent 
  its 
  heing 
  placed 
  in 
  the 
  same 
  genus. 
  

   The 
  shell, 
  too, 
  is 
  thinner, 
  and 
  there 
  is 
  an 
  entire 
  absence 
  of 
  radial 
  

   structure 
  and 
  of 
  external 
  sculpture. 
  

  

  With 
  Lticinopsis, 
  and 
  as 
  a 
  sub-genus, 
  I 
  would 
  place 
  the 
  Veneritapes 
  

   of 
  Cossmann 
  for 
  the 
  reasons 
  already 
  given. 
  With 
  regard 
  to 
  Cooperella 
  

   it 
  seems 
  to 
  me 
  to 
  come 
  very 
  near 
  these 
  two 
  forms, 
  and 
  as 
  the 
  internal 
  

   resilium 
  is 
  very 
  variable 
  in 
  its 
  development, 
  so 
  that 
  it 
  is 
  sometimes 
  

   merely 
  an 
  extension 
  of 
  the 
  ligament, 
  the 
  differences 
  in 
  the 
  shell 
  are 
  

   small. 
  The 
  mantle 
  of 
  the 
  animal 
  is 
  much 
  more 
  widely 
  open 
  than 
  in 
  

   the 
  case 
  of 
  Lucinopsis, 
  and 
  some 
  observers 
  may 
  regard 
  this 
  as 
  a 
  generic 
  

   character. 
  Dr. 
  Dall 
  is 
  evidently 
  of 
  this 
  opinion, 
  and 
  in 
  deference 
  to 
  

   it 
  I 
  retain 
  Cooperella 
  as 
  a 
  genus. 
  

  

  Ciiclinella 
  and 
  Claudiconcha 
  I 
  provisionally 
  exclude 
  from 
  the 
  family 
  

   because 
  there 
  is 
  not 
  yet 
  sufficient 
  evidence 
  for 
  removing 
  the 
  one 
  

   from 
  Cyclina 
  and 
  the 
  other 
  from 
  Venerup)is. 
  The 
  Petrieolidse 
  may 
  

   therefore 
  be 
  regarded 
  as 
  consisting 
  of 
  the 
  following 
  generic 
  and 
  sub- 
  

   generic 
  groups 
  : 
  — 
  

  

  