﻿ECHINODERMATA. 
  161 
  

  

  line 
  of 
  junction 
  of 
  the 
  second 
  and 
  third. 
  Distichals 
  2 
  ; 
  palmars 
  2 
  : 
  

   in 
  neither 
  case 
  is 
  the 
  axillary 
  a 
  syzygy, 
  and 
  in 
  both 
  cases 
  there 
  is 
  a 
  

   slight 
  conical 
  protuberance 
  where 
  the 
  two 
  joints 
  meet, 
  and 
  in 
  both 
  

   cases 
  also 
  the 
  more 
  proximal 
  of 
  the 
  two 
  joints 
  is 
  in 
  close 
  lateral 
  

   contact 
  with 
  its 
  fellow. 
  First 
  brachials 
  a 
  little 
  wider 
  along 
  their 
  

   outer 
  than 
  their 
  inner 
  side 
  ; 
  along 
  the 
  latter 
  they 
  are 
  again 
  in 
  close 
  

   contact 
  with 
  their 
  fellow 
  ; 
  as 
  the 
  second 
  brachial 
  is 
  also 
  wider 
  

   without 
  than 
  within, 
  there 
  is 
  a 
  feebly-marked 
  diamond-space 
  

   interval. 
  The 
  third 
  brachial 
  is 
  nearly 
  oblong, 
  and, 
  being 
  syzygial, 
  

   has 
  somewhat 
  the 
  appearance 
  of 
  a 
  dice-box. 
  For 
  the 
  next 
  three 
  

   or 
  four 
  joints 
  there 
  is 
  no 
  wedge-shaped 
  arrangement 
  ; 
  at 
  first 
  

   feebly 
  indicated, 
  it 
  rapidly 
  becomes 
  more 
  marked 
  ; 
  further 
  out 
  it 
  

   diminishes, 
  and 
  the 
  terminal 
  joints 
  are 
  nearly 
  oblong. 
  As 
  in 
  

   A. 
  jlageUata 
  (see 
  Carpenter, 
  Notes 
  Leyd. 
  Mus. 
  iii. 
  p. 
  183), 
  the 
  

   earlier 
  brachials 
  are 
  flattened 
  on 
  their 
  outer 
  side. 
  

  

  The 
  first 
  syzygy 
  is 
  on 
  the 
  third 
  brachial, 
  the 
  next 
  about 
  the 
  

   fifteenth, 
  and 
  there 
  are 
  then 
  intervals 
  of 
  9-10 
  joints 
  between 
  the 
  

   syzygies. 
  

  

  The 
  species 
  is 
  at 
  once 
  to 
  be 
  distinguished 
  from 
  A. 
  Jlagellata 
  by 
  

   the 
  fact 
  that 
  the 
  third 
  is 
  shorter 
  than 
  the 
  first 
  pinnule 
  ; 
  of 
  the 
  first 
  

   three 
  the 
  second 
  is 
  the 
  longest. 
  The 
  first 
  is 
  on 
  the 
  second 
  brachial, 
  

   and 
  is 
  but 
  little 
  shorter 
  than 
  the 
  second 
  ; 
  the 
  first 
  three 
  pinnules 
  

   all 
  have 
  broad 
  basal 
  and 
  elongated 
  distal 
  joints, 
  but 
  though 
  longer 
  

   than 
  the 
  next 
  succeeding 
  they 
  are 
  by 
  no 
  means 
  remarkable 
  in 
  their 
  

   length. 
  

  

  Colour 
  : 
  brownish 
  flesh-coloured 
  arms 
  ; 
  the 
  peristome 
  very 
  much 
  

   darker 
  ; 
  the 
  cirri 
  much 
  darker 
  on 
  their 
  ventral 
  than 
  their 
  dorsal 
  

   aspect. 
  

  

  Disk 
  incised, 
  with 
  a 
  diameter 
  of 
  7*5 
  millim. 
  ; 
  arms 
  about 
  

   80 
  millim. 
  long 
  ; 
  cirri 
  21 
  millim. 
  long. 
  

  

  Thursday 
  Island. 
  

  

  12. 
  Antedon 
  irregularis. 
  (Plate 
  XIII. 
  figs. 
  A, 
  a-c.) 
  

  

  Centrodorsal 
  fiattened, 
  small 
  ; 
  cirri 
  marginal, 
  in 
  two 
  rows, 
  about 
  

   25 
  in 
  number 
  (but 
  there 
  may 
  be 
  not 
  more 
  than 
  15), 
  with 
  30-35 
  

   joints, 
  the 
  lowermost 
  short, 
  fourth 
  to 
  ninth 
  longer 
  than 
  wide, 
  then 
  

   again 
  shortening 
  ; 
  no 
  spine, 
  except 
  on 
  the 
  penultimate 
  joint, 
  and 
  

   that 
  exceedingly 
  small. 
  

  

  First 
  radials 
  not 
  (or 
  barely) 
  visible 
  ; 
  second 
  wide, 
  in 
  contact, 
  

   with 
  a 
  median 
  convex 
  protuberance 
  ; 
  the 
  third 
  almost 
  perfectly 
  tri- 
  

   angular. 
  

  

  Arms 
  11-22. 
  Three 
  joints 
  in 
  the 
  first 
  division, 
  the 
  axillaries 
  

   syzygies 
  ; 
  when 
  there 
  is 
  a 
  second 
  division 
  there 
  are 
  two 
  joints, 
  the 
  

   axillaries 
  not 
  syzygies. 
  The 
  earlier 
  joints 
  of 
  the 
  arm 
  have 
  a 
  well- 
  

   rounded 
  convex 
  dorsal 
  surface 
  and 
  are 
  broader 
  than 
  long 
  ; 
  soon, 
  

   however, 
  they 
  become 
  very 
  markedly 
  wedge-shaped 
  and 
  form 
  a 
  

   prominent 
  projection 
  alternately 
  on 
  either 
  side. 
  Towards 
  the 
  end 
  

   of 
  the 
  arms 
  these 
  disappear. 
  

  

  