﻿F.CHINODEKMATA. 
  127 
  

  

  the 
  ossicles 
  have 
  diminished 
  in 
  proportional 
  thickness 
  while 
  in- 
  

   creasing 
  in 
  length, 
  and 
  so 
  having 
  lost 
  their 
  earlier 
  stoutness, 
  now 
  

   require 
  external 
  aid; 
  and 
  (c) 
  a 
  final 
  condition, 
  in 
  which 
  equilibrium 
  

   is 
  again 
  established, 
  the 
  ossicles 
  themselves 
  being 
  again 
  stouter, 
  — 
  or 
  

   whether 
  we 
  have 
  to 
  do 
  with 
  two 
  sets 
  of 
  variations 
  from 
  a 
  common 
  

   stock, 
  due 
  to 
  some 
  slight 
  differences 
  in 
  the 
  environment. 
  But 
  this 
  

   is 
  a 
  complex 
  and 
  difficult 
  question, 
  which 
  can 
  only 
  be 
  satisfactorily 
  

   answered 
  by 
  one 
  who 
  has 
  at 
  hand 
  the 
  living 
  wealth 
  of 
  the 
  Aus- 
  

   tralian 
  seas. 
  

  

  Port 
  Curtis 
  ; 
  Fitzroy 
  Island 
  ; 
  Albany 
  Island 
  ; 
  Port 
  Denison, 
  

   8-12 
  fms. 
  

  

  10. 
  Linckia, 
  sp. 
  

  

  A 
  very 
  small 
  specimen, 
  from 
  West 
  Island, 
  Torres 
  Strait, 
  presents 
  

   that 
  interesting 
  peculiarity 
  of 
  three 
  smaller 
  and 
  three 
  larger 
  arms, 
  

   hinting 
  thereby 
  at 
  a 
  division 
  of 
  the 
  disk 
  instead 
  of 
  gemmation 
  from 
  

   a 
  single 
  arm; 
  it 
  is 
  the 
  smallest 
  heteractinic 
  Lmclcla 
  I 
  have 
  seen, 
  the 
  

   longest 
  arm 
  measuring 
  only 
  G 
  millim. 
  

  

  11. 
  Anthenea 
  flavescens. 
  

  

  Perrier, 
  p. 
  276. 
  

  

  Port 
  Jackson, 
  0-5 
  fms. 
  

  

  The 
  Museum 
  collection 
  contains 
  also 
  specimens 
  of 
  this 
  species 
  

   from 
  Fremantle, 
  W. 
  Australia. 
  

  

  12. 
  Oreaster 
  gracilis. 
  

  

  Pentaceros 
  gracilis, 
  Perrier, 
  p. 
  246. 
  

  

  Oreaster 
  gracilis, 
  Liitken, 
  Vid. 
  Med. 
  1871, 
  pp. 
  260, 
  261. 
  

  

  A 
  selected 
  series 
  of 
  five 
  specimens, 
  all 
  from 
  Port 
  Denison 
  (4 
  fms.), 
  

   exhibit 
  remarkably 
  well 
  the 
  great 
  change 
  which 
  occurs 
  in 
  this 
  

   species, 
  even 
  after 
  a 
  considerable 
  size 
  has 
  been 
  attained. 
  The 
  

   smallest, 
  which 
  has 
  E, 
  equal 
  to 
  93-5 
  millim., 
  has 
  five 
  tubercles, 
  

   about 
  10 
  millim. 
  high, 
  one 
  at 
  the 
  central 
  end 
  of 
  each 
  median 
  row 
  

   of 
  tubercles 
  : 
  in 
  another, 
  with 
  R 
  equal 
  to 
  108 
  millim., 
  the 
  

   tubercles, 
  though 
  a 
  little 
  stronger, 
  are 
  no 
  higher 
  and 
  are 
  here 
  only 
  

   to 
  be 
  found 
  on 
  three 
  of 
  the 
  angles 
  of 
  the 
  disk 
  ; 
  this 
  specimen, 
  like 
  

   another 
  which 
  is 
  a 
  little 
  larger, 
  has 
  the 
  lateral 
  and 
  marginal 
  spines 
  

   very 
  well 
  developed: 
  two 
  specimens, 
  with 
  P 
  equal 
  to 
  118 
  and 
  

   140 
  millim, 
  respectively, 
  have 
  these 
  spines 
  less 
  well 
  developed, 
  and 
  

   the 
  diminution 
  is 
  the 
  more 
  marked 
  in 
  the 
  larger 
  specimen 
  ; 
  the 
  

   smaller 
  has 
  one 
  large 
  central 
  tubercle, 
  and 
  the 
  larger 
  has 
  each 
  of 
  

   the 
  whole 
  set 
  of 
  five 
  reduced 
  to 
  growths 
  which 
  are 
  hardly 
  larger 
  

   than 
  the 
  other 
  spines 
  on 
  the 
  disk. 
  

  

  A 
  specimen 
  with 
  six 
  arms, 
  one 
  of 
  which 
  has 
  been 
  injured 
  and 
  

   has 
  commenced 
  to 
  grow 
  again, 
  was 
  collected 
  at 
  Port 
  Molle. 
  

  

  