﻿ECHINODEKMATA. 
  163 
  

  

  14. 
  Antedon 
  briareus. 
  (Plate 
  XIV,) 
  

  

  Centrodorsal 
  flattened 
  ; 
  15-20 
  marginal 
  delicate 
  cirri, 
  formed 
  of 
  

   a 
  few 
  short 
  joints. 
  

  

  Arms 
  more 
  than 
  70. 
  

  

  First 
  radials 
  obscured 
  ; 
  second 
  in 
  contact, 
  at 
  least 
  three 
  times 
  as 
  

   long 
  as 
  they 
  are 
  broad 
  ; 
  third 
  widely 
  triangular. 
  Three 
  distichals, 
  

   the 
  axillary 
  a 
  syzygy 
  ; 
  two 
  palmars. 
  If 
  there 
  is 
  another 
  division 
  

   there 
  are 
  again 
  two 
  joints 
  ; 
  no 
  syzygy. 
  The 
  first 
  five 
  or 
  six 
  brachials 
  

   have 
  nearly 
  even 
  edges 
  ; 
  the 
  succeeding 
  ones 
  are 
  markedly 
  wedge- 
  

   shaped. 
  A 
  syzygy 
  on 
  the 
  third 
  brachial 
  ; 
  succeeding 
  syzygies 
  rare. 
  

  

  Second 
  pinnules 
  longer 
  than 
  first, 
  very 
  delicate, 
  made 
  up 
  of 
  a 
  

   number 
  of 
  small 
  joints 
  ; 
  the 
  succeeding 
  pinnules 
  stouter 
  and 
  more 
  

   fleshy. 
  

  

  This 
  is 
  one 
  of 
  the 
  species 
  in 
  which 
  there 
  is 
  a 
  very 
  considerable 
  

   difference 
  in 
  the 
  length 
  of 
  the 
  arms 
  ; 
  here 
  some 
  of 
  the 
  arms 
  may 
  be 
  

   as 
  much 
  as 
  110 
  millim. 
  long, 
  while 
  others 
  are 
  only 
  75 
  millim. 
  

   There 
  is 
  an 
  interradial 
  plating, 
  extending 
  as 
  far 
  as 
  the 
  distichal 
  

   axillary. 
  

  

  The 
  colour 
  (in 
  spirit) 
  is 
  dark 
  brown. 
  

  

  Port 
  Denison. 
  

  

  15. 
  Antedon 
  microdiscus. 
  (Plate 
  XV.) 
  

  

  Centrodorsal 
  rather 
  large 
  a»d 
  prominent 
  ; 
  the 
  cirri 
  marginal, 
  in 
  

   two 
  or 
  three 
  rows, 
  from 
  30-50 
  in 
  number, 
  with 
  from 
  50-70 
  joints, 
  

   none 
  of 
  which 
  are 
  markedly 
  longer 
  than 
  broad 
  ; 
  as 
  a 
  rule, 
  the 
  distal 
  

   two 
  thirds 
  have 
  an 
  inconspicuous 
  dorsal 
  spine, 
  and 
  in 
  the 
  larger 
  

   specimen 
  the 
  penultimate 
  spine 
  is 
  hardly 
  more 
  conspicuous. 
  

  

  The 
  first 
  radials 
  visible 
  ; 
  all 
  very 
  short 
  and 
  wide, 
  the 
  second 
  not 
  

   in 
  contact. 
  Three 
  distichals, 
  the 
  axillary 
  a 
  syzygy. 
  Three 
  palmars, 
  

   the 
  axillary 
  normally 
  a 
  syzj-gy. 
  The 
  arms 
  may 
  divide 
  again, 
  and 
  of 
  

   the 
  three 
  joints 
  the 
  axillary 
  may 
  or 
  may 
  not 
  be 
  a 
  syzygy. 
  Probably 
  

   as 
  many 
  as 
  90 
  arms 
  in 
  an 
  adult. 
  The 
  earlier 
  brachials 
  have 
  fairly 
  

   even 
  edges, 
  are 
  well 
  rounded 
  above 
  and 
  fiattened 
  at 
  their 
  sides 
  ; 
  the 
  

   next 
  succeeding 
  are 
  faintly 
  wedge-shaped, 
  the 
  distal 
  edge 
  of 
  each 
  

   projecting 
  alternately 
  on 
  either 
  side 
  into 
  a 
  slight 
  protuberance 
  ; 
  

   further 
  out, 
  the 
  wedge-form 
  disappears. 
  The 
  arms 
  generally, 
  though 
  

   slender, 
  are 
  very 
  firm 
  and 
  stiff 
  and 
  are 
  set 
  verj' 
  close 
  to 
  one 
  another. 
  

  

  Syzygies 
  3, 
  22-25, 
  40-41; 
  then 
  from 
  10-12 
  joints 
  between 
  

   each. 
  

  

  The 
  earlier 
  pinnules 
  exceedingly 
  long 
  in 
  the 
  adult, 
  with 
  very 
  

   stout 
  slightly 
  keeled 
  basal 
  joints 
  ; 
  the 
  second, 
  which 
  is 
  a 
  good 
  deal 
  

   longer 
  than 
  the 
  first, 
  has 
  as 
  many 
  as 
  50 
  joints 
  and 
  is 
  qiiite 
  fine 
  at 
  

   its 
  free 
  end 
  ; 
  the 
  more 
  distal 
  joints 
  are 
  provided 
  with 
  a 
  spine 
  or 
  tuft 
  

   of 
  spines. 
  

  

  The 
  stiff 
  straight 
  arms 
  are 
  about 
  150 
  millim. 
  long; 
  the 
  cirri 
  

   measure 
  nearly 
  50 
  millim. 
  ; 
  the 
  disk, 
  with 
  rounded 
  incisions, 
  has 
  a 
  

   diameter 
  of 
  about 
  12 
  millim. 
  

  

  The 
  disk 
  and 
  the 
  arms, 
  as 
  far 
  as 
  their 
  last 
  division, 
  are 
  largely 
  

  

  m2 
  

  

  