﻿Genera 
  of 
  Recent 
  Clypeastroids. 
  595 
  

  

  easily 
  determined. 
  Leske 
  included 
  only 
  four 
  species 
  in 
  his 
  

   genus 
  {humilis, 
  alius, 
  ovatus, 
  orbiculatus), 
  and 
  of 
  these 
  

   humilis 
  equals 
  rosaceus, 
  L., 
  and 
  with 
  its 
  near 
  relative 
  alius 
  

   belongs 
  in 
  Clypeaster, 
  where 
  they 
  were 
  placed 
  by 
  Lamarck. 
  

   In 
  1825 
  Gray 
  lemoved 
  ovatus 
  to 
  his 
  new 
  genus 
  Echino- 
  

   lanipas, 
  and 
  therefore 
  orbiculatus 
  alone 
  is 
  left 
  to 
  be 
  the 
  type 
  

   of 
  Echinanthus. 
  As 
  this 
  species 
  is 
  generally 
  agreed 
  to 
  be 
  a 
  

   Pygurus, 
  Agassiz, 
  the 
  latter 
  name 
  becomes 
  a 
  synonym 
  of 
  

   Echinanthus, 
  unless 
  it 
  contains, 
  as 
  established 
  by 
  Agassiz, 
  

   one 
  or 
  more 
  species 
  not 
  congeneric 
  with 
  orbiculatus, 
  Leske. 
  

  

  If, 
  then, 
  the 
  name 
  Echinanthus 
  is 
  no 
  longer 
  available 
  for 
  a 
  

   clypeastroid, 
  and 
  if 
  Clypeaster, 
  Lamarck, 
  must 
  replace 
  

   Echinanthus 
  as 
  used 
  by 
  A. 
  Agassiz, 
  what 
  is 
  the 
  proper 
  name 
  

   for 
  the 
  group 
  called 
  Clypeaster 
  in 
  the 
  ' 
  Revision 
  ' 
  ? 
  Personally 
  

   I 
  think 
  it 
  is 
  practically 
  impossible 
  to 
  separate. 
  the 
  two 
  groups. 
  

   It 
  is 
  true 
  that 
  the 
  internal 
  structure 
  of 
  the 
  test 
  of 
  rosaceus 
  

   is 
  strikingly 
  different 
  from 
  its 
  West-Indian 
  ally 
  subdepressus, 
  

   Gray; 
  but 
  one 
  cannot 
  separate 
  the 
  Pacific 
  forms' 
  by 
  a 
  corre- 
  

   sponding 
  difference, 
  and 
  I 
  think 
  we 
  must 
  consider 
  the 
  

   condition 
  in 
  rosaceus 
  as 
  simply 
  a 
  specific 
  character. 
  There 
  

   can 
  be 
  no 
  doubt 
  that 
  increasing 
  age 
  brings 
  an 
  increasing 
  

   amount 
  of 
  calcareous 
  matter 
  for 
  deposit 
  in 
  the 
  test 
  of 
  clype- 
  

   astroids, 
  and 
  we 
  must 
  therefore 
  be 
  on 
  our 
  guard 
  against 
  

   placing 
  too 
  much 
  weight 
  upon 
  characters 
  shown 
  by 
  the 
  

   internal 
  structure 
  of 
  the 
  test. 
  If, 
  however, 
  it 
  is 
  desirable 
  to 
  

   distinguish 
  rosaceus 
  geuerically 
  from 
  its 
  nearest 
  allies, 
  the 
  

   latter 
  may 
  bear 
  the 
  name 
  Stolonoclypus 
  proposed 
  by 
  

   A. 
  Agassiz 
  in 
  1863. 
  The 
  type 
  of 
  this 
  genus 
  I 
  will 
  here 
  

   designate 
  as 
  Clypeaster 
  prostratus, 
  Ravenel, 
  = 
  Echinanthus 
  

   subdepressa, 
  Gray. 
  

  

  The 
  species 
  called 
  reticulatus 
  by 
  Linne 
  is 
  a 
  more 
  inexcu- 
  

   sable 
  composite 
  than 
  rosaceus, 
  as 
  it 
  is 
  made 
  up 
  of 
  two 
  utterly 
  

   unlike 
  clypeastroids 
  : 
  one 
  is 
  rosaceus 
  itself, 
  as 
  clearly 
  shown 
  

   by 
  Sloane's 
  figures 
  to 
  which 
  Linne 
  refers 
  ; 
  while 
  the 
  other, 
  

   indicated 
  by 
  references 
  to 
  Gualthierfs 
  pi. 
  ex. 
  fig. 
  D, 
  is 
  the 
  

   little 
  Indo-Pacific 
  species 
  long 
  known 
  as 
  Clypeaster 
  scuti- 
  

   formis 
  (Grnel.). 
  The 
  difference 
  in 
  Linne 
  5 
  s 
  diagnoses 
  of 
  

   rosaceus 
  and 
  reticulatus 
  is 
  so 
  trivial 
  that 
  it 
  needs 
  no 
  con- 
  

   sideration. 
  LoveVs 
  attempt 
  in 
  1887 
  (/. 
  c.) 
  to 
  delimit 
  reticu* 
  

   latus 
  was 
  anticipated 
  over 
  a 
  century 
  earlier 
  by 
  Leske, 
  who, 
  

   in 
  1778, 
  clearly 
  restricted 
  the 
  name 
  reticulatus 
  to 
  the 
  Indo- 
  

   Pacific 
  form. 
  As 
  A. 
  Agassiz 
  showed 
  this 
  in 
  the 
  ' 
  Revision/ 
  

   I 
  am 
  at 
  a 
  loss 
  to 
  understand 
  why 
  he 
  preferred 
  the 
  later 
  name 
  

   scutiformis. 
  

  

  Returning 
  again 
  to 
  Linne's 
  list, 
  we 
  find 
  the 
  fourth 
  species 
  

   (orbiculus) 
  recognized 
  as 
  a 
  composite 
  by 
  its 
  author, 
  who 
  

  

  