﻿ECHINODEEMATA. 
  511 
  

  

  b 
  

  

  3 
  A' 
  -, 
  which 
  seems 
  to 
  be 
  new 
  to 
  science, 
  but 
  of 
  which 
  more 
  mature 
  

  

  specimens 
  must 
  be 
  obtained 
  before 
  the 
  species 
  can 
  be 
  named 
  and 
  

   described. 
  

  

  From 
  the 
  He 
  des 
  Roches, 
  which 
  is 
  on 
  a 
  separate 
  coral-bank 
  from 
  

   the 
  other 
  islands, 
  came 
  : 
  — 
  

  

  Phj'llacanthus 
  baculosus 
  (13 
  fms.). 
  

  

  At 
  Providence 
  Island, 
  which 
  is 
  240 
  miles 
  S.W. 
  by 
  S. 
  of 
  the 
  

   Amirante 
  group, 
  the 
  only 
  Echinoderm 
  obtained 
  was 
  

  

  Opbiothrix 
  propinqua. 
  

  

  This 
  species 
  seems 
  to 
  be 
  somewhat 
  variable 
  in 
  the 
  details 
  of 
  its 
  

   coloration 
  ; 
  originally 
  described 
  by 
  Lyman 
  as 
  having 
  a 
  blue 
  mark- 
  

   ing, 
  some 
  specimens 
  collected 
  by 
  the 
  ' 
  Challenger 
  ' 
  were 
  reported 
  by 
  

   that 
  eminent 
  authority 
  as 
  " 
  red 
  varieties," 
  Such 
  are 
  most 
  of 
  the 
  

   specimens 
  in 
  the 
  present 
  collection. 
  

  

  From 
  Glorioso 
  Islands 
  come 
  : 
  — 
  

  

  Ophiocoma 
  scolopendrina 
  and 
  flolothuria 
  pardalis. 
  

  

  In 
  addition 
  to 
  the 
  more 
  or 
  less 
  well-known 
  species 
  of 
  Ophiurids 
  

   the 
  names 
  of 
  which 
  have 
  just 
  been 
  given, 
  the 
  collection 
  contains 
  

   examples 
  of 
  some 
  very 
  remarkable 
  forms 
  which, 
  so 
  far 
  as 
  I 
  am 
  able 
  

   to 
  tell, 
  have 
  not 
  yet 
  received 
  description 
  at 
  the 
  hands 
  of 
  any 
  

   naturalist. 
  

  

  In 
  one 
  case 
  I 
  feel 
  justified 
  in 
  establishing 
  a 
  new 
  genus, 
  for 
  

   which, 
  as 
  the 
  term 
  Hemiijlax 
  is 
  already 
  in 
  use, 
  I 
  propose 
  that 
  of 
  

   Neoi)lax. 
  

  

  NEOPLAX. 
  

  

  Disk 
  covered 
  with 
  a 
  rather 
  thick 
  skin, 
  not 
  richly 
  granulated. 
  No 
  

   radial 
  shields 
  ; 
  the 
  dorsal 
  arm-platos 
  present, 
  but 
  incompletely 
  

   developed 
  and 
  not 
  touching 
  one 
  another. 
  Arms 
  long, 
  slender, 
  

   coiled 
  on 
  themselves, 
  but 
  not 
  divided. 
  A 
  few 
  mouth-papilla; 
  and 
  a 
  

   few 
  teeth, 
  but 
  no 
  fringe 
  of 
  spines 
  to 
  either. 
  A 
  moderate 
  number 
  of 
  

   short 
  arm-spines, 
  with 
  their 
  basal 
  portions 
  embedded 
  in 
  the 
  skin. 
  

   The 
  tentacle-scale 
  single 
  and 
  very 
  small. 
  The 
  genital 
  slits 
  long 
  

   and 
  the 
  scale 
  large. 
  

  

  This 
  interesting 
  genus 
  appears 
  to 
  belong 
  to 
  Mr. 
  Lyman's 
  third 
  

   group 
  of 
  Ophiurida3, 
  or 
  the 
  Astrojihi/ton-Yike 
  Ophiurans. 
  Notwith- 
  

   standing 
  the 
  absence 
  of 
  radial 
  shields, 
  it 
  does 
  not 
  seem 
  to 
  have 
  any 
  

   special 
  affinity 
  to 
  Opluomyces 
  ; 
  but, 
  on 
  the 
  whole, 
  to 
  stand 
  not 
  very 
  

   far 
  from 
  Opldomijxa, 
  from 
  which, 
  however, 
  it 
  is 
  to 
  be 
  distinguished 
  

   (1) 
  by 
  the 
  complete 
  absence 
  of 
  radial 
  shields, 
  (2) 
  the 
  great 
  reduction 
  

   of 
  the 
  plates 
  at 
  the 
  margin 
  of 
  the 
  disk, 
  (3) 
  the 
  twisted 
  arms, 
  and 
  

   (4) 
  the 
  absence 
  of 
  the 
  modified 
  spines 
  on 
  the 
  oral 
  processes. 
  . 
  

  

  