﻿GOO 
  Mr. 
  H. 
  L. 
  Clark 
  on 
  the 
  

  

  parts, 
  a 
  numeral 
  and 
  a 
  participle, 
  might 
  be 
  construed 
  as 
  an 
  

   indication 
  that 
  the 
  full 
  names 
  {Echino 
  discus 
  guinyuies 
  

   perforatus 
  or 
  5 
  perforatus 
  and 
  E. 
  sexies 
  perforatus 
  or 
  6 
  per- 
  

   foratus) 
  are 
  not 
  binomial, 
  and 
  this 
  would 
  clear 
  the 
  way 
  for 
  

   Gmelin's 
  names 
  ; 
  but 
  this 
  seems 
  to 
  me 
  such 
  an 
  unworthy 
  

   quibble, 
  I 
  cannot 
  bring 
  myself 
  to 
  adopt 
  it. 
  

  

  Other 
  genera 
  which 
  have 
  been 
  suggested 
  at 
  different 
  times 
  

   for 
  Recent 
  clypeastroids 
  seem 
  to 
  me 
  to 
  lack 
  sufficient 
  reason 
  

   for 
  being. 
  Thus 
  the 
  genera 
  Diplothecanthus 
  and 
  Plesianthus, 
  

   Duncan, 
  are 
  due 
  to 
  the 
  recognition 
  of 
  the 
  wrong 
  type 
  for 
  

   Clypeaster 
  and 
  the 
  laying 
  of 
  too 
  much 
  stress 
  on 
  the 
  internal 
  

   structure 
  of 
  C. 
  rosaceus. 
  Mellitella 
  is 
  based 
  on 
  a 
  remarkable 
  

   misconception 
  by 
  Duncan 
  of 
  the 
  character 
  of 
  its 
  type 
  species, 
  

   Mellita 
  stokesii 
  (Agass.). 
  He 
  states 
  that 
  the 
  lunules 
  remain 
  

   open 
  as 
  marginal 
  slits. 
  It 
  is 
  possible 
  that 
  he 
  drew 
  this 
  con- 
  

   clusion 
  from 
  the 
  figure 
  given 
  by 
  A. 
  Agassiz 
  in 
  the 
  ' 
  Revision 
  ' 
  ; 
  

   but 
  he 
  would 
  have 
  avoided 
  error 
  had 
  he 
  read 
  the 
  description 
  

   given 
  in 
  that 
  work, 
  for 
  Agassiz 
  distinctly 
  says 
  that 
  the 
  

   lunules 
  may 
  be 
  completely 
  closed, 
  as 
  in 
  other 
  species 
  of 
  

   Mellita. 
  I 
  may 
  add 
  here 
  that 
  I 
  think 
  there 
  is 
  no 
  longer 
  any 
  

   good 
  reason 
  for 
  doubting 
  that 
  stokesiiis 
  simply 
  the 
  young 
  of 
  

   Eucope 
  micropora 
  ; 
  hence 
  Mellitella 
  becomes 
  a 
  synonym 
  of 
  

   Eucope. 
  The 
  genus 
  Moulinia 
  — 
  or 
  Moulinsia 
  as 
  emended 
  by 
  

   Duncan, 
  — 
  established 
  by 
  Agassiz 
  in 
  1841 
  for 
  a 
  little 
  clype- 
  

   astroid 
  from 
  Martinique, 
  is 
  maintained 
  by 
  Duncan, 
  1885, 
  

   although 
  Liitken 
  and 
  A. 
  Agassiz 
  considered 
  its 
  type 
  to 
  be 
  a 
  

   young 
  Eucope. 
  A 
  re-examination 
  of 
  the 
  available 
  evidence 
  

   has 
  satisfied 
  me 
  that 
  Liitken 
  and 
  A. 
  Agassiz 
  were 
  right, 
  and 
  

   I 
  have 
  therefore 
  discarded 
  the 
  name. 
  

  

  The 
  more 
  one 
  considers 
  the 
  various 
  characters 
  by 
  which 
  

   the 
  families 
  and 
  genera 
  of 
  the 
  clypeastroids 
  are 
  to 
  be 
  distin- 
  

   guished, 
  the 
  clearer 
  it 
  becomes 
  that 
  the 
  position 
  of 
  the 
  

   auricles 
  and 
  their 
  relation 
  to 
  each 
  other 
  is 
  of 
  very 
  great 
  

   importance, 
  although 
  little 
  weight 
  has 
  been 
  attached 
  to 
  it 
  

   hitherto. 
  The 
  condition 
  of 
  theactinal 
  ambulacral 
  furrows 
  is 
  

   also 
  an 
  important 
  character, 
  and 
  fortunately 
  is 
  easily 
  

   observed. 
  The 
  arrangement 
  and 
  relative 
  size 
  of 
  the 
  inter- 
  

   ambulacral 
  plates 
  are 
  characters 
  usually 
  difficult 
  to 
  make 
  out 
  

   in 
  adults, 
  and 
  as 
  they 
  are 
  almost 
  certainly 
  correlated 
  with 
  

   the 
  shape 
  of 
  the 
  test, 
  too 
  much 
  stress 
  should 
  not 
  be 
  laid 
  on 
  

   them. 
  It 
  is 
  hard 
  to 
  decide 
  how 
  much 
  weight 
  may 
  properly 
  

   be 
  given 
  to 
  the 
  arrangement 
  of 
  the 
  internal 
  calcareous 
  

   supports. 
  It 
  is 
  hard 
  to 
  believe 
  that 
  it 
  is 
  of 
  any 
  great 
  signifi- 
  

   cance, 
  and 
  it 
  seems 
  almost 
  certain 
  that 
  the 
  differences 
  are, 
  

   in 
  part 
  at 
  least, 
  due 
  to 
  age. 
  The 
  distinction 
  between 
  

  

  