﻿lEEDALK 
  & 
  may: 
  MISNAMED 
  TASMANIAN 
  CHITONS. 
  103 
  

  

  represents 
  gimnii. 
  This 
  conclusion 
  necessitates 
  the 
  redetermination 
  

   of 
  South 
  Australian 
  shells 
  and 
  also 
  West 
  Australian 
  ones. 
  Torr 
  lias 
  

   sent 
  a 
  few 
  South 
  Australian 
  shells, 
  and 
  here 
  again 
  two 
  very 
  distinct 
  

   sjjecies 
  are 
  confused, 
  and 
  it 
  may 
  even 
  prove 
  that 
  more 
  may 
  be 
  

   lecognized. 
  The 
  exact 
  application 
  of 
  the 
  name 
  siriatiis 
  is 
  not 
  yet 
  

   certain, 
  for 
  we 
  have 
  not 
  ascertained 
  the 
  existence 
  of 
  the 
  type, 
  and 
  

   the 
  description 
  is 
  very 
  inadequate 
  and 
  no 
  exact 
  locality 
  is 
  given, 
  

   though 
  Peron 
  and 
  Lesueur 
  are 
  cited 
  as 
  the 
  collectors'; 
  this 
  fact 
  

   suggests 
  King 
  Island. 
  

  

  6. 
  IscnNocHiroNs. 
  

   Tasmania 
  appears 
  to 
  be 
  very 
  rich 
  in 
  species 
  referred 
  to 
  Ischnockiton 
  , 
  

   S.I., 
  but 
  the 
  south 
  has 
  developed 
  a 
  most 
  wonderful 
  fauna 
  of 
  large 
  

   species, 
  while 
  the 
  north 
  has 
  many 
  Adelaidean 
  forms. 
  Torr 
  recorded 
  

   twenty 
  species 
  of 
  Ischnochiton 
  from 
  South 
  Australia, 
  and 
  the 
  majority 
  

   of 
  these 
  may 
  yet 
  be 
  found 
  in 
  northern 
  Tasmania. 
  Pilsbry, 
  when 
  

   dealing 
  with 
  Port 
  Jackson 
  Chitons, 
  admitted 
  five 
  subgenera, 
  viz. 
  

   Ischiochiton, 
  s.s., 
  Eeterozona, 
  Stenochiton, 
  naploplax, 
  and 
  hcimoradsia. 
  

   Thiele 
  was 
  more 
  conservative 
  still, 
  for, 
  dismissingi7fl/;/oju/r/.c 
  altogether,- 
  

   he 
  only 
  regarded 
  Stenochiton, 
  Ileterozona, 
  and 
  Isehioradsia 
  as 
  sections 
  

   of 
  the 
  subgenus 
  Ischnoclnton. 
  Stenochiton 
  and 
  Ischioradsia 
  are 
  super- 
  

   ficially 
  so 
  different 
  that 
  generic 
  segregation 
  is 
  demanded. 
  The 
  general 
  

   form 
  of 
  Ilaphplax 
  differentiates 
  this 
  group, 
  and 
  the 
  girdle-scales 
  

   being 
  very 
  different 
  from 
  those 
  of 
  Ischnochiton 
  we 
  consider 
  the 
  name 
  

   should 
  have 
  generic 
  rank. 
  However, 
  we 
  would 
  record 
  that 
  neither 
  

   mayii 
  nor 
  virgatus 
  have 
  any 
  place 
  in 
  the 
  group. 
  Adult 
  Ileterozona 
  

   IS 
  a 
  very 
  chaiaeteristic 
  shell 
  in 
  the 
  peculiar 
  girdle-scaling, 
  and 
  we 
  

   propose 
  to 
  use 
  this 
  name 
  generically 
  for 
  somewhat 
  novel 
  reasons. 
  

   Firstly, 
  the 
  immature 
  Heterozona 
  cariosa 
  has 
  the 
  girdle-scaling 
  

   normal, 
  the 
  scales 
  being 
  regular 
  but 
  smaller 
  on 
  tlie 
  outer 
  half 
  of 
  the 
  

   girdle. 
  This 
  is 
  the 
  regular 
  girdle-scale 
  formation 
  in 
  such 
  a 
  species 
  

   as 
  fruticosns, 
  Gould, 
  and 
  to 
  some 
  extent 
  in 
  the 
  species 
  known 
  as 
  

   "contractus 
  " 
  (recte 
  lineolattis, 
  Blainville). 
  In 
  the 
  species 
  known 
  as 
  

   '' 
  divergens" 
  {vt'Gte 
  prote 
  us, 
  Keeve) 
  and 
  crispus, 
  Peeve, 
  the 
  scales 
  are 
  

   practically 
  uniform 
  in 
  size 
  to 
  the 
  edge 
  of 
  the 
  girdle. 
  Therefore, 
  if 
  

   Ileterozona 
  were 
  to 
  be 
  enlarged, 
  it 
  might 
  reasonablv 
  include 
  such 
  

   shells 
  as 
  fruticosus, 
  Gould. 
  While 
  we 
  do 
  not 
  take 
  this 
  step 
  at 
  this 
  

   time 
  we 
  use 
  Ileterozona 
  generically, 
  as 
  we 
  describe 
  a 
  new 
  species 
  from 
  

   southern 
  Tasmania 
  which 
  is 
  tlie 
  most 
  highly 
  developed 
  of 
  the 
  group 
  

   yet 
  known. 
  In 
  this 
  the 
  peculiar 
  girdle 
  covering 
  is 
  developed 
  at 
  an 
  

   early 
  age, 
  and 
  is 
  most 
  noticeable 
  at 
  tlie 
  first 
  glance. 
  We 
  would 
  thus 
  

   make 
  use 
  of 
  Pilsbry's 
  five 
  subgenera 
  as 
  genera, 
  and 
  if 
  these 
  are 
  

   utilized 
  closer 
  examination 
  of 
  shells 
  becomes 
  necessary 
  and 
  fewer 
  

   mistakes 
  will 
  be 
  made. 
  Again, 
  we 
  must 
  note 
  that 
  long 
  series 
  are 
  

   necessary, 
  as 
  the 
  very 
  immature 
  of 
  many 
  Ischnochitons 
  are 
  quite 
  alike 
  

   in 
  form, 
  lack 
  of 
  sculpture, 
  and 
  girdle-scaling. 
  I'urther, 
  the 
  giidle- 
  

   scales 
  of 
  juvenile 
  specimens 
  appreciably 
  differ 
  from 
  those 
  of 
  the 
  

   aduU, 
  even 
  when 
  the 
  latter 
  are 
  not 
  referable 
  to 
  Heterozona. 
  

  

  Since 
  the 
  preceding 
  was 
  written 
  we 
  have 
  been 
  surprised 
  by 
  the 
  

   dissections 
  of 
  the 
  new 
  species 
  /. 
  mawlei. 
  A 
  peculiar 
  and 
  beautiful 
  

  

  