﻿125 
  

  

  HAS 
  LYMN^A 
  AN 
  AURICULOID 
  ANCESTRY.? 
  

  

  By 
  Chaklks 
  Hedley, 
  F.L.S., 
  etc. 
  

  

  Read 
  10th 
  November, 
  1916. 
  

  

  Critical 
  study 
  of 
  fluviatile 
  faunas 
  has 
  lately 
  broken 
  up 
  the 
  alliances 
  

   of 
  former 
  classifications 
  and 
  frequently 
  ascribes 
  to 
  each 
  smaller 
  group 
  

   an 
  independent 
  origin 
  from 
  marine 
  species. 
  

  

  Thus 
  the 
  Lymnaeidae 
  of 
  Fischer's 
  Manual 
  has 
  been 
  divided 
  since 
  

   1883 
  into 
  Lymnseidse, 
  Planorbidae, 
  Ancylidae, 
  and 
  Pliysidaj, 
  while 
  

   Chilina 
  is 
  regarded 
  by 
  Dr. 
  H. 
  A. 
  Pilsbry 
  as 
  having 
  arisen 
  in 
  

   South 
  America 
  from 
  a 
  marine 
  parent. 
  From 
  what 
  marine 
  type 
  did 
  

   Lyynncea 
  come 
  ? 
  

  

  Judging 
  from 
  its 
  radula, 
  Mr. 
  F. 
  C. 
  Baker 
  proposed 
  for 
  Lymncea 
  

   "a 
  descent 
  from 
  the 
  Tectibranchiate 
  stock 
  of 
  marine 
  mollusks 
  ".' 
  

   It 
  is 
  now 
  suggested 
  that 
  the 
  Ellobiidse 
  may 
  stand 
  closer 
  to 
  Lymnma 
  

   than 
  any 
  Tectibranch. 
  

  

  Phytia 
  ornata 
  (Ferussac). 
  Upper 
  and 
  under 
  view 
  of 
  the 
  animal 
  crawling. 
  

  

  In 
  shell 
  features 
  the 
  remarkable 
  strongly-twisted 
  pillar 
  of 
  Lymncea 
  

   may 
  answer 
  to 
  the 
  prominent 
  columella 
  folds 
  so 
  radical 
  a 
  character 
  of 
  

   the 
  Ellobiidse. 
  The 
  animal 
  of 
  Lymncea 
  is 
  well 
  known, 
  but 
  there 
  are 
  

   few 
  drawings, 
  or 
  descriptions 
  from 
  life, 
  of 
  the 
  auriculoids. 
  The 
  

   following 
  notes 
  which 
  prompted 
  the 
  query 
  at 
  the 
  head 
  of 
  this 
  paper 
  

   are 
  therefore 
  advanced 
  for 
  comparison. 
  

  

  Phytia 
  ornata, 
  Ferussac,- 
  is 
  abundant 
  and 
  widespread 
  in 
  South-East 
  

   Australia 
  and 
  Tasmania. 
  Its 
  habits 
  are 
  to 
  associate 
  with 
  Rhodostoma, 
  

   Salinator, 
  and 
  Assemannia, 
  in 
  the 
  Snlicornia 
  zone, 
  that 
  is 
  just 
  below 
  

   high-water 
  level 
  in 
  sheltered 
  estuarine 
  swamps, 
  either 
  in 
  the 
  open 
  or 
  

  

  1 
  Baker: 
  Chicago 
  Acad. 
  Sci., 
  Spec. 
  Publ. 
  No. 
  3, 
  1911, 
  p. 
  9. 
  

  

  2 
  Hedley: 
  Proc. 
  Linn. 
  See. 
  New 
  South 
  Wales, 
  xxxviii, 
  1913, 
  p. 
  334. 
  

  

  