﻿110 
  rUOCEEDIXGS 
  OF 
  TUK 
  MALACOLOGICAL 
  SOCIETY. 
  

  

  having 
  13 
  slits, 
  old 
  shell 
  9 
  slits, 
  median 
  valve 
  1 
  slit, 
  tail-valve 
  in 
  

   young 
  shell 
  13 
  slits, 
  in 
  old 
  shell 
  11 
  slits. 
  

  

  Type 
  from 
  Port 
  Arthur, 
  southern 
  Tasmania, 
  collected 
  by 
  E. 
  ^lawle. 
  

   Length 
  41, 
  breadth 
  19 
  mm. 
  Largest 
  shell 
  : 
  length 
  59, 
  breadth 
  27 
  mm. 
  

  

  Ilange: 
  coasts 
  of 
  Tasmania. 
  

  

  This 
  species 
  differs 
  from 
  I. 
  pyotem^ 
  lleeve, 
  in 
  the 
  finer 
  sculpture 
  of 
  

   the 
  terminal 
  valves 
  and 
  lateral 
  areas 
  of 
  the 
  median 
  valves, 
  while 
  the 
  

   pleura 
  shows 
  much 
  coarser 
  sculpture. 
  It 
  grows 
  to 
  a 
  much 
  larger 
  

   size, 
  and 
  the 
  scales 
  of 
  the 
  girdle 
  are 
  comparatively 
  smaller. 
  

   Compared 
  with 
  a 
  typical 
  specimen 
  of 
  proteus 
  of 
  the 
  same 
  size, 
  the 
  

   anterior 
  valves 
  show 
  40 
  ribs, 
  the 
  laterals 
  6-8, 
  the 
  posterior 
  40 
  ribs, 
  

   as 
  against 
  anterior 
  o.3, 
  the 
  laterals 
  4-7, 
  the 
  posterior 
  28-30 
  for 
  proteus 
  

   ( 
  1*1. 
  V, 
  Fig. 
  2a'"). 
  The 
  figures 
  will 
  show 
  the 
  differences, 
  which 
  become 
  

   emphasized 
  as 
  larger 
  specimens 
  are 
  examined. 
  

  

  13. 
  IscnNOcniTON 
  atkinsoni, 
  n.sp, 
  PI. 
  IV, 
  Fig. 
  3. 
  

  

  Shell 
  small, 
  elongate 
  oval, 
  elevated, 
  round-backed, 
  valves 
  not 
  

   beaked. 
  Colour 
  uniform 
  buff. 
  Anterior 
  valve 
  coarsely 
  quincuncially 
  

   punctate, 
  though 
  obscure 
  radials 
  can 
  be 
  distinguished 
  ; 
  the 
  type- 
  

   specimen 
  figured 
  is 
  half-grown 
  only, 
  since 
  the 
  valves 
  become 
  eroded 
  

   and 
  brittle 
  at 
  a 
  very 
  early 
  stage. 
  In 
  the 
  senile 
  shell 
  obscure 
  radials 
  

   predominate 
  on 
  the 
  anterior 
  valve. 
  Median 
  valves 
  have 
  the 
  pleural 
  

   areas 
  coarsely 
  quincunciallj' 
  pustulose, 
  the 
  pustules 
  round, 
  flat-topped, 
  

   and 
  finer 
  on 
  the 
  jugum, 
  which 
  is 
  always 
  much 
  eroded 
  in 
  senile 
  shells. 
  

   The 
  lateral 
  areas 
  are 
  well 
  elevated, 
  pustulose 
  only 
  in 
  the 
  adult, 
  

   coarse, 
  nodulous 
  radials 
  being 
  developed 
  with 
  age, 
  that 
  are, 
  however, 
  

   dominated 
  by 
  the 
  concentric 
  growth-lines 
  so 
  that 
  they 
  appear 
  as 
  if 
  

   concentrically 
  granulose. 
  The 
  posterior 
  valve 
  is 
  pustulose 
  in 
  the 
  

   immature 
  stage, 
  which 
  first 
  shows 
  the 
  develo})ment 
  of 
  stronger 
  

   sculpture. 
  In 
  the 
  senile 
  shell 
  the 
  mucro 
  is 
  elevated 
  and 
  central, 
  the 
  

   posterior 
  slope 
  slightly 
  convex, 
  sculptured 
  with 
  apparently 
  elongate 
  

   nodules, 
  caused 
  by 
  the 
  intersection 
  of 
  the 
  radials 
  with 
  tlie 
  growth- 
  

   lines. 
  Girdle-scales 
  regular, 
  very 
  small, 
  and 
  finely 
  striate. 
  Interiud 
  

   coloration 
  white; 
  slits 
  normally 
  Ischnoid, 
  nine 
  in 
  anterior 
  valve, 
  

   one 
  in 
  median 
  valves 
  on 
  each 
  side, 
  eleven 
  in 
  posterior 
  valve. 
  

  

  Type 
  collected 
  by 
  Mr. 
  E. 
  D. 
  Atkinson, 
  J.P., 
  at 
  Sulphur 
  Creek, 
  

   northern 
  Tasmania. 
  

  

  Length 
  8, 
  breadth 
  4'5 
  mm. 
  Senile 
  shell 
  : 
  length 
  13, 
  breadth 
  7 
  mm. 
  

   Dried 
  shells. 
  

  

  liunge: 
  northern 
  Tasmania. 
  Also 
  collected 
  by 
  Dr. 
  Torr. 
  

  

  The 
  minute 
  striated 
  scales 
  of 
  the 
  girdle 
  at 
  once 
  distinguished 
  this 
  

   small 
  species 
  from 
  the 
  immature 
  of/, 
  decoratus 
  (Sykes), 
  and 
  there 
  is 
  

   at 
  present 
  no 
  other 
  species 
  with 
  which 
  it 
  can 
  be 
  confused. 
  It 
  

   suggested 
  "■gryei^^ 
  recorded 
  by 
  Dr. 
  Torr 
  from 
  South- 
  Australia, 
  but 
  

   we 
  find 
  it 
  quite 
  distinct, 
  as 
  will 
  later 
  be 
  shown. 
  

  

  14. 
  Chiton 
  ustdlatus, 
  Heeve. 
  

  

  Angas, 
  in 
  1807, 
  recorded 
  Lepidopleurus 
  ustulatus 
  (lleeve) 
  from 
  Port 
  

  

  Jackson. 
  Pilsbry 
  (Proc. 
  Acad. 
  JN^at. 
  Sci., 
  1894, 
  p. 
  70, 
  footnote) 
  

  

  commented 
  ''■ 
  Ischnochiton 
  udulatus, 
  Reeve, 
  occurs 
  abundantly 
  in 
  

  

  South 
  Australia, 
  but 
  nothing 
  I 
  have 
  seen 
  from 
  Port 
  Jackson 
  

  

  