﻿ECHINODERMATA. 
  159 
  

  

  syzj-gy. 
  Ten 
  arms. 
  First 
  brachials 
  wider 
  without 
  than 
  williin, 
  in 
  

   contact, 
  with 
  a 
  convex 
  median 
  protuberance 
  along 
  their 
  distal 
  edge 
  ; 
  

   the 
  second 
  with 
  sides 
  a 
  little 
  more 
  regular 
  ; 
  the 
  third 
  almost 
  square, 
  

   a 
  syzygy. 
  The 
  fourth 
  to 
  seventh 
  joints 
  a 
  little 
  wider 
  than 
  long; 
  

   eighth 
  or 
  ninth 
  a 
  syzygy. 
  The 
  succeeding 
  joints 
  wedge-shaped, 
  

   with 
  their 
  free 
  margins 
  a 
  little 
  overlapping 
  and 
  slightly 
  toothed. 
  

   About 
  5-8 
  joints 
  between 
  the 
  succeeding 
  syzygies. 
  

  

  The 
  earlier 
  pinnules 
  are 
  extraordinarily 
  stiff; 
  the 
  first, 
  which 
  is 
  

   on 
  the 
  second 
  brachial, 
  is 
  much 
  shorter 
  than 
  the 
  second 
  or 
  third, 
  

   which 
  are 
  of 
  about 
  the 
  same 
  length 
  and 
  made 
  up 
  of 
  rather 
  less 
  than 
  

   20 
  joints, 
  most 
  of 
  which 
  are 
  longer 
  than 
  wide, 
  and 
  have 
  their 
  distal 
  

   edge 
  enlarged 
  and 
  slightly 
  denticulated. 
  There 
  are 
  10 
  or 
  }2 
  stiff 
  

   pinnules 
  ; 
  the 
  succeeding 
  ones 
  are 
  shorter, 
  and 
  then 
  again 
  longer. 
  

  

  Arras 
  more 
  than 
  120 
  millim. 
  long 
  ; 
  disk 
  not 
  more 
  than 
  7 
  millim. 
  

   in 
  diameter. 
  The 
  radials 
  and 
  the 
  earlier 
  brachials 
  have 
  their 
  

   infero-lateral 
  edge 
  produced 
  into 
  a 
  kind 
  of 
  ledge. 
  The 
  more 
  

   proximal 
  joints 
  have 
  the 
  appearance 
  of 
  being 
  tuberculated, 
  and 
  

   there 
  is 
  a 
  taint 
  median 
  dorsal 
  ridge 
  ; 
  at 
  the 
  sides 
  they 
  are 
  com- 
  

   pressed. 
  

  

  Colour 
  dark 
  slate. 
  

  

  The 
  stiff 
  pinnules, 
  the 
  long 
  arms, 
  and 
  the 
  small 
  disk 
  are 
  very 
  

   striking 
  characters 
  in 
  this 
  species. 
  

  

  Port 
  Denison. 
  

  

  The 
  large 
  Myzostomum 
  found 
  on 
  it 
  has 
  been 
  named 
  M. 
  coriaceum 
  

   by 
  Dr. 
  Graff. 
  

  

  8. 
  Antedon 
  decipiens. 
  (Plate 
  XI. 
  figs. 
  B, 
  a.) 
  

  

  Centrodorsal 
  small 
  ; 
  drri 
  on 
  three 
  levels, 
  about 
  20 
  in 
  number, 
  

   with 
  25 
  joints, 
  of 
  which 
  the 
  fourth 
  to 
  tenth 
  are 
  longer 
  than 
  wide 
  ; 
  

   the 
  rest, 
  which 
  gradually 
  become 
  shorter, 
  are 
  provided 
  with 
  a 
  well- 
  

   marked 
  spine 
  ; 
  these 
  decrease 
  towards 
  the 
  end, 
  but 
  the 
  penultimate 
  

   one 
  is 
  larger 
  again. 
  

  

  First 
  radials 
  quite 
  distinct 
  ; 
  the 
  second 
  oblong, 
  three 
  times 
  as 
  

   long 
  as 
  wide, 
  partly 
  in 
  contact 
  ; 
  the 
  third 
  almost 
  triangular. 
  The 
  

   arms 
  may 
  or 
  may 
  not 
  divide, 
  so 
  that 
  there 
  are 
  from 
  about 
  14 
  to 
  18. 
  

   The 
  first 
  brachials 
  or 
  first 
  distichals 
  are 
  always 
  wide, 
  and 
  touch 
  ; 
  

   where 
  the 
  arms 
  divide 
  there 
  are 
  three 
  distichals, 
  and 
  the 
  axillary 
  

   may 
  be 
  a 
  syzygy. 
  The 
  first 
  brachials, 
  which 
  have 
  sharp 
  overlapping 
  

   distal 
  edges, 
  are 
  pretty 
  regularly 
  oblong 
  ; 
  at 
  about 
  the 
  seventh 
  they 
  

   become 
  alternately 
  wider 
  on 
  either 
  side, 
  to 
  again 
  become 
  more 
  

   regular 
  later 
  on. 
  

  

  Syzygies 
  3, 
  12-15, 
  22-25; 
  then 
  from 
  ] 
  0-12 
  joints 
  between 
  each 
  

   syzygy. 
  

  

  First 
  pinnule 
  on 
  second 
  distichal 
  (when 
  present), 
  that 
  and 
  the 
  

   one 
  on 
  the 
  third 
  brachial 
  short 
  ; 
  those 
  on 
  fifth 
  to 
  ninth 
  much 
  lon"-er 
  

   the 
  basal 
  joints 
  very 
  stout, 
  the 
  free 
  ends 
  very 
  delicate, 
  and 
  their 
  

   outer 
  side 
  produced 
  into 
  a 
  well-marked 
  conicfti 
  process. 
  The 
  suc- 
  

   ceeding 
  pinnules 
  are 
  shorter, 
  and 
  these 
  again 
  increase 
  in 
  length 
  • 
  

   they 
  are 
  not 
  composed 
  of 
  a 
  large 
  number 
  of 
  joiuts. 
  

  

  