﻿Anatomy 
  q/'Paljeechinus 
  (Scolder), 
  M'Coy. 
  205 
  

  

  and 
  primaries 
  subequal, 
  and 
  there 
  is 
  no 
  crowding 
  to 
  form 
  

   demi-plates 
  or 
  to 
  crush 
  out 
  parts 
  of 
  plates 
  from 
  the 
  interradial 
  

   sutures. 
  The 
  plates 
  are 
  Cidaridean 
  in 
  their 
  simplicity 
  and 
  

   each 
  has 
  a 
  pair 
  of 
  pores, 
  so 
  that 
  there 
  is 
  one 
  vertical 
  series 
  on 
  

   each 
  side 
  of 
  an 
  ambulacrum. 
  This 
  is 
  the 
  case 
  with 
  P. 
  quadri- 
  

   serialis 
  and 
  with 
  the 
  small 
  Palceechinus 
  in 
  the 
  Woodwardian 
  

   Museum. 
  It 
  must 
  be 
  admitted 
  that 
  the 
  alliance 
  is 
  close, 
  but 
  

   these 
  species 
  cannot 
  enter 
  the 
  same 
  genus 
  as 
  P. 
  gigas 
  for 
  

   instance. 
  Unfortunately 
  M'Coy 
  was 
  not 
  impressed 
  with 
  the 
  

   value 
  of 
  the 
  ambulacral 
  characters, 
  and 
  placed 
  P. 
  gigas, 
  

   P. 
  elegans, 
  P. 
  ellipticus, 
  P. 
  sphcericus 
  and 
  another 
  as 
  types 
  

   of 
  his 
  genus 
  Palceechinus 
  (M'Coy, 
  in 
  Griffith, 
  Foss. 
  Carb. 
  

   Limest. 
  Irel. 
  1842, 
  p. 
  171, 
  see 
  pi. 
  xxiv 
  ), 
  every 
  ambulacrum 
  

   being 
  wrongly 
  figured 
  by 
  his 
  artist. 
  W. 
  Keeping 
  was 
  

   clearly 
  impressed 
  with 
  the 
  want 
  of 
  homogeneity 
  in 
  the 
  genus 
  ; 
  

   and 
  when 
  he 
  met 
  with 
  the 
  specimen 
  in 
  the 
  Woodwardian 
  Mu- 
  

   seum, 
  which 
  has 
  a 
  small 
  test 
  with 
  small 
  plates 
  and 
  straight, 
  

   single, 
  vertical 
  rows 
  of 
  pairs 
  of 
  pores, 
  one 
  series 
  of 
  pairs 
  only 
  

   being 
  found 
  upon 
  each 
  side 
  of 
  an 
  ambulacrum, 
  he 
  defined 
  a 
  new 
  

   genus 
  Rhoechinus 
  (op. 
  cit. 
  p. 
  37). 
  Really 
  this 
  genus, 
  with 
  a 
  

   very 
  slight 
  modification, 
  will 
  embrace 
  the 
  forms 
  of 
  Palce- 
  

   echinus 
  witli 
  uni 
  serial 
  pairs 
  of 
  pores. 
  

  

  From 
  our 
  present 
  knowledge, 
  if 
  Palceechinus 
  is 
  to 
  remain 
  as 
  

   a 
  genus 
  — 
  and 
  it 
  ought 
  to 
  do 
  so, 
  for 
  M'Coy's 
  work 
  claims 
  

   great 
  respect 
  — 
  it 
  must 
  be 
  as 
  Palceechinus, 
  M'Coy 
  (pars), 
  and 
  

   relate 
  to 
  species 
  with 
  a 
  double 
  vertical 
  row 
  of 
  pairs 
  of 
  pores, 
  

   such 
  as 
  P. 
  gigas 
  and 
  P. 
  sphcericus. 
  Rhoechinus, 
  Keeping, 
  

   slightly 
  modified, 
  will 
  then 
  contain 
  P. 
  elegans, 
  possibly 
  P. 
  

   quadriserialis, 
  and 
  certainly 
  the 
  little 
  form 
  in 
  the 
  Wood- 
  

   wardian 
  Museum. 
  

  

  Synonymy. 
  

  

  Genus 
  Palceechinus, 
  M'Coy, 
  pars. 
  

  

  P. 
  gigas, 
  P. 
  sphcericus, 
  P. 
  ellipticus, 
  P. 
  intermedins, 
  

   P. 
  Phillips 
  ice. 
  

  

  Genus 
  Rhoechinus, 
  Keeping. 
  

  

  R. 
  irregularis, 
  Keeping 
  ; 
  R. 
  elegans, 
  M'Coy, 
  sp. 
  ; 
  R. 
  quadri- 
  

   serialis, 
  J. 
  Wright, 
  sp. 
  ; 
  R. 
  sp. 
  (in 
  the 
  Woodwardian 
  

   Museum, 
  named 
  a 
  Palceechinus). 
  

  

  The 
  two 
  North-American 
  species, 
  which 
  I 
  have 
  not 
  seen, 
  

   Ann. 
  & 
  Mag. 
  N. 
  Hist. 
  Ser. 
  6. 
  Vol. 
  iii. 
  15 
  

  

  