﻿58 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.98 
  

  

  Acknowledgments 
  are 
  due 
  Dr. 
  Henry 
  van 
  der 
  Schalie, 
  who 
  kindly 
  

   sent 
  living 
  specimens 
  from 
  which 
  dissections 
  were 
  made. 
  The 
  

   majority 
  of 
  the 
  locality 
  records 
  were 
  sent 
  by 
  Dr. 
  van 
  der 
  Schalie 
  from 
  

   the 
  world's 
  largest 
  Pomatiopsis 
  collection 
  at 
  the 
  Museum 
  of 
  Zoology, 
  

   University 
  of 
  Michigan. 
  William 
  J. 
  Clench, 
  curator 
  of 
  the 
  depart- 
  

   ment 
  of 
  mollusks, 
  Museum 
  of 
  Comparative 
  Zoology, 
  at 
  Cambridge, 
  

   Mass., 
  generously 
  made 
  his 
  collection 
  and 
  its 
  facilities 
  available 
  for 
  

   part 
  of 
  this 
  study. 
  Dissections 
  and 
  bibliographic 
  research 
  v\-ere 
  made 
  

   b/Oth 
  at 
  Cambridge 
  and 
  at 
  the 
  division 
  of 
  mo.llusks 
  at 
  the 
  United 
  

   States 
  National 
  Museum. 
  

  

  Family 
  AMNICOLIDAE 
  

   Subfamily 
  Hydrobiinae 
  

  

  The 
  genus 
  Pomatiopsis 
  Tryon, 
  1862, 
  is 
  being 
  placed 
  in 
  the 
  family 
  

   Amnicolidae 
  and 
  the 
  subfamily 
  Hydrobiinae. 
  Various 
  authors 
  in 
  the 
  

   past 
  have 
  put 
  Pomatiopsis 
  in 
  a 
  subfamily 
  and 
  even 
  family 
  of 
  its 
  own. 
  

   However, 
  in 
  all 
  its 
  characters, 
  animal, 
  shell, 
  and 
  operculum, 
  it 
  is 
  prop- 
  

   erly 
  a 
  hydrobiine. 
  We 
  believe 
  it 
  should 
  appear 
  alongside 
  the 
  genus 
  

   Oncotnelania. 
  

  

  The 
  genus 
  Pomatiopsis 
  in 
  North 
  America 
  contains 
  a 
  number 
  of 
  spe- 
  

   cies 
  whose 
  anatomical 
  features 
  have 
  not 
  as 
  yet 
  been 
  investigated 
  and 
  a 
  

   complete 
  monograph 
  will 
  have 
  to 
  await 
  further 
  study. 
  A 
  catalog 
  of 
  

   the 
  American 
  species 
  of 
  Pomatiopsis 
  is 
  appended 
  at 
  the 
  end 
  of 
  this 
  

   paper. 
  

  

  POMATIOPSIS 
  LAPIDARIA 
  (Say) 
  

  

  Cyclostoma 
  lapidaria 
  Say, 
  Journ. 
  Acad. 
  Nat. 
  Sci. 
  Philadelphia, 
  vol. 
  1, 
  p. 
  13, 
  1817 
  

  

  (no 
  locality). 
  

   Amnicola 
  {Pomatiopsis) 
  lapidaria 
  Say, 
  Tryon, 
  Proc. 
  Acad. 
  Nat. 
  Sci. 
  Philadelphia, 
  

  

  1862, 
  p. 
  451. 
  . 
  

   Pomatiopsis 
  lapidaria 
  Say, 
  Stimpson, 
  Smithsouian 
  Misc. 
  Coll., 
  vol. 
  7, 
  No. 
  201, 
  pp. 
  

  

  31-36, 
  1865. 
  

  

  Description 
  of 
  shell. 
  — 
  Adult 
  shell 
  5 
  to 
  8 
  mm. 
  (about 
  one-fourth 
  inch) 
  

   in 
  length, 
  elongate-ovate, 
  thin 
  ; 
  color 
  a 
  translucent 
  chocolate-brown 
  to 
  

   light 
  yellowish 
  brown. 
  Nuclear 
  whorls 
  (developed 
  in 
  egg 
  mass) 
  2 
  

   in 
  number, 
  rounded 
  and 
  glassy. 
  Postnuclear 
  whorls 
  (developed 
  after 
  

   hatching) 
  4 
  to 
  5 
  in 
  number, 
  well 
  rounded, 
  smooth 
  except 
  for 
  many 
  

   small 
  axial 
  lines 
  of 
  growth. 
  Suture 
  between 
  whorls 
  well 
  indented. 
  

   Base 
  of 
  last 
  whorl 
  short, 
  rounded, 
  w-ith 
  a 
  narrow, 
  fairly 
  deep 
  umbili- 
  

   cus. 
  On 
  rare 
  occasions 
  an 
  adult 
  maj^ 
  have 
  a 
  slightly 
  thickened 
  outer 
  

   lip 
  of 
  the 
  aperture, 
  though 
  usually 
  this 
  aperture 
  lip 
  is 
  thin 
  and 
  sharp. 
  

   Operculum 
  very 
  thin, 
  transparent, 
  paucispiral, 
  with 
  eccentric 
  nucleus 
  

   and 
  2 
  to 
  3 
  whorls. 
  ( 
  See 
  pi. 
  3, 
  figs. 
  3 
  and 
  4. 
  ) 
  

  

  The 
  shell 
  of 
  P. 
  lapidaria 
  is 
  strikingly 
  similar 
  to 
  Oncomelania 
  no- 
  

   sophora 
  (Robson) 
  of 
  Japan 
  and 
  China, 
  differing 
  only 
  in 
  having 
  

   the 
  whorls 
  more 
  globose 
  and 
  the 
  umbilicus 
  larger 
  and 
  lacking 
  in 
  

  

  