﻿OLD 
  AND 
  NEW 
  WORLD 
  MELANIANS 
  — 
  ^MORRISON 
  369 
  

  

  evident 
  also 
  that 
  the 
  western 
  American 
  (Alaskan) 
  region 
  consti- 
  

   tuted 
  the 
  pathway 
  of 
  migration 
  of 
  these 
  fresh-water 
  mollusks 
  between 
  

   Asia 
  and 
  North 
  America. 
  

  

  Genus 
  Paludomus 
  Swainson, 
  1840 
  

  

  With 
  a 
  short, 
  ovate 
  shell-shape 
  corresponding 
  to 
  that 
  of 
  the 
  Ameri- 
  

   can 
  genus 
  Leptoxis, 
  the 
  Asiatic 
  genus 
  Paludomus 
  (Swainson, 
  1840, 
  

   pp. 
  198, 
  340) 
  also 
  belongs 
  to 
  the 
  subfamily 
  Pleurocerinae. 
  The 
  

   anatomy 
  of 
  the 
  animals 
  of 
  Paludomus 
  tanschaurica 
  (Gmelin) 
  has 
  

   been 
  completely 
  studied 
  by 
  Seshaiya 
  (1934). 
  The 
  finding 
  by 
  Seshaiya 
  

   of 
  a 
  tubular 
  structure 
  which 
  he 
  called 
  a 
  "penis" 
  along 
  the 
  terminal 
  

   portion 
  of 
  the 
  primary 
  gonoduct 
  of 
  the 
  male 
  must 
  be 
  discounted 
  as 
  

   a 
  glandular 
  discovery 
  until 
  it 
  is 
  proven 
  to 
  be 
  an 
  intromittent 
  organ. 
  

   As 
  Seshaiya 
  himself 
  pointed 
  out, 
  it 
  is 
  not 
  muscular 
  as 
  is 
  the 
  case 
  

   of 
  the 
  similarly 
  located 
  and 
  functional 
  male 
  organ 
  of 
  the 
  Tiphobiinae. 
  

   Seshaiya 
  believed 
  these 
  animals 
  oviparous, 
  as 
  he 
  found 
  no 
  evidence 
  of 
  

   ovoviviparity 
  in 
  their 
  anatomy. 
  He 
  did 
  not, 
  however, 
  mention 
  either 
  

   the 
  egg-laying 
  groove 
  or 
  the 
  pit. 
  Paludomus 
  labiosus 
  (Benson) 
  (?) 
  

   from 
  Thailand 
  and 
  Paludomus 
  maculatus 
  Lea 
  from 
  India 
  (also 
  

   members 
  of 
  the 
  subgenus 
  Paludomus, 
  sensu 
  stricto, 
  with 
  its 
  concentric 
  

   operculum) 
  have 
  been 
  personally 
  examined. 
  The 
  female 
  animals 
  are 
  

   pleurocerine, 
  with 
  an 
  egg-laying 
  groove 
  and 
  pit 
  in 
  the 
  side 
  of 
  the 
  foot 
  

   and 
  without 
  any 
  brood 
  pouch 
  (see 
  pi. 
  11, 
  fig. 
  6). 
  The 
  true 
  biological 
  

   relations 
  of 
  the 
  other 
  subgenera 
  such 
  as 
  Hemimitra, 
  which 
  differ 
  

   markedly 
  in 
  shell 
  and 
  opercular 
  characters, 
  are 
  still 
  unknown 
  or 
  

   unrecorded. 
  

  

  Subfamily 
  lavigeriinae 
  Thiele, 
  1929 
  

  

  Members 
  of 
  the 
  subfamily 
  Lavigeriinae 
  Thiele 
  (1929, 
  p. 
  79) 
  show 
  

   the 
  full 
  dioecious 
  mode 
  of 
  reproduction 
  of 
  the 
  family. 
  That 
  is, 
  there 
  

   is 
  a 
  normal 
  1:1 
  sex 
  ratio 
  of 
  males 
  to 
  females 
  as 
  in 
  all 
  other 
  known 
  

   members 
  of 
  the 
  Pleuroceridae. 
  The 
  most 
  important 
  distinguishing 
  

   character 
  is 
  the 
  possession 
  of 
  a 
  uterine 
  brood 
  pouch 
  similar 
  to 
  that 
  in 
  

   the 
  Viviparidae. 
  As 
  in 
  the 
  typical 
  subfamily 
  (Pleurocerinae), 
  the 
  

   males 
  possess 
  no 
  intromittent 
  structures 
  whatsoever. 
  Coincident 
  to 
  

   the 
  development 
  of 
  ovoviviparity, 
  the 
  females 
  have 
  lost 
  (at 
  least 
  do 
  

   not 
  possess) 
  the 
  egg-laying 
  sinus 
  and 
  papilla 
  characteristic 
  of 
  the 
  

   Pleurocerinae. 
  The 
  name 
  Semisulcospirinae 
  Morrison 
  (1952, 
  p. 
  8) 
  is 
  

   a 
  synonym 
  of 
  the 
  earUer 
  subfamily 
  name 
  Lavigeriinae. 
  

  

  Genus 
  Semisulcospira 
  Boettger, 
  1886 
  

  

  The 
  genotype 
  of 
  Semisulcospira 
  Boettger 
  (1886, 
  p. 
  4) 
  is 
  the 
  well- 
  

   Icnown 
  Japanese 
  species 
  Semisulcospira 
  libertina 
  (Gould) 
  1862. 
  Ex- 
  

   amination 
  of 
  many 
  specimens 
  from 
  the 
  Hayakawa^River, 
  ^Honshu, 
  

  

  273553—54 
  3 
  

  

  