﻿598 
  Mr. 
  II. 
  L. 
  Clark 
  on 
  the 
  

  

  Bull. 
  Inst. 
  Egypt, 
  (4) 
  iv.) 
  confirms 
  A. 
  Agassiz's 
  view 
  that 
  

   the 
  two 
  are 
  identical, 
  it 
  is 
  desirable 
  to 
  have 
  decided 
  which 
  is 
  

   the 
  typical 
  form. 
  

  

  Leslie's 
  genus 
  Echinocyamus 
  contains 
  thirteen 
  nominal 
  

   species, 
  all 
  based 
  on 
  Van 
  Phelsum' 
  s 
  figures. 
  Lamarck 
  

   (1816) 
  includes 
  the 
  same 
  group, 
  so 
  far 
  as 
  he 
  recognizes 
  them 
  

   at 
  all, 
  in 
  his 
  genus 
  Fibularia. 
  The 
  two 
  names 
  were 
  used 
  

   interchangeably 
  for 
  many 
  years, 
  some 
  writers 
  using 
  Leske's 
  

   and 
  others 
  preferring 
  Lamarck's, 
  until, 
  in 
  1847, 
  Agassiz 
  

   and 
  Desor 
  (Ann. 
  Sci. 
  Nat. 
  (3) 
  vii. 
  pp. 
  140-142) 
  restricted 
  

   Echinocyamus 
  to 
  the 
  flat 
  forms 
  (" 
  Oursins 
  plat") 
  and 
  Fibu- 
  

   laria 
  to 
  the 
  high 
  ones 
  (" 
  Forme 
  subspherique 
  ou 
  ovo'ide 
  "). 
  

   As 
  angulosus 
  is 
  the 
  only 
  one 
  of 
  Leske's 
  thirteen 
  species 
  

   which 
  they 
  mention, 
  and 
  as 
  it 
  stands 
  first 
  in 
  their 
  list 
  of 
  

   Echinocyamus 
  species, 
  it 
  may 
  well 
  be 
  considered 
  the 
  type 
  of 
  

   that 
  genus. 
  Under 
  Fibularia 
  they 
  mention 
  two 
  of 
  Lamarck's 
  

   species, 
  ovuluni 
  and 
  triyona 
  ; 
  but 
  as 
  the 
  former 
  is 
  now 
  

   generally 
  considered 
  a 
  synonym 
  of 
  the 
  latter, 
  trigona 
  is 
  

   doubtless 
  the 
  type 
  of 
  the 
  genus. 
  

  

  Were 
  the 
  history 
  of 
  the 
  name 
  Echinarachnius 
  exactly 
  as 
  

   recounted 
  in 
  the 
  ' 
  Revision 
  of 
  the 
  Echini,' 
  it 
  would 
  be 
  im- 
  

   possible 
  for 
  us 
  to 
  retain 
  it 
  for 
  the 
  sand-dollars 
  in 
  the 
  sense 
  

   in 
  which 
  it 
  has 
  been 
  used 
  for 
  seventy 
  years; 
  but 
  fortunately 
  

   quite 
  another 
  interpretation 
  of 
  Leske's 
  use 
  of 
  the 
  name 
  than 
  

   that 
  given 
  in 
  the 
  ' 
  Revision 
  ' 
  is 
  not 
  only 
  permissible, 
  but 
  is 
  

   apparently 
  more 
  reasonable. 
  On 
  p. 
  153 
  of 
  his 
  ' 
  Additamenta 
  

   ad 
  Klein 
  ' 
  Leske 
  refers 
  to 
  a 
  clypeastroid 
  under 
  a 
  " 
  Genus 
  1 
  " 
  

   which 
  he 
  says 
  Van 
  Phelsum 
  called 
  Echinarachnius 
  , 
  and 
  on 
  

   the 
  next 
  page 
  (154) 
  he 
  describes 
  it 
  as 
  iC 
  Species 
  74, 
  Echin- 
  

   arachnius." 
  Further 
  on 
  he 
  says 
  it 
  is 
  identical 
  with 
  Echinus 
  

   placenta. 
  L. 
  Van 
  Phelsum, 
  however, 
  did 
  not 
  call 
  the 
  animal 
  

   Echinarachnius, 
  and 
  on 
  p. 
  8 
  Leske 
  himself 
  translates 
  Van 
  

   Phelsum's 
  colloquial 
  name 
  as 
  Arachnoides, 
  which 
  is 
  Klein's 
  

   " 
  Genus 
  unicum" 
  and 
  obviously 
  Leske's 
  " 
  Genus 
  1." 
  Is 
  it 
  

   not 
  clear, 
  then, 
  that 
  it 
  is 
  no 
  mistake 
  of 
  Leske's 
  in 
  calling 
  

   Echinarachnius 
  a 
  species 
  rather 
  than 
  a 
  genus 
  ? 
  He 
  evidently 
  

   intends 
  to 
  retain 
  Klein's 
  name 
  Arachnoides 
  for 
  the 
  genus, 
  

   and 
  as 
  Klein 
  gives 
  no 
  specific 
  name, 
  Leske 
  proposes 
  echin- 
  

   arachnius, 
  but 
  states 
  that 
  it 
  is 
  equivalent 
  to 
  placenta, 
  L. 
  

   Gray 
  (1825, 
  op. 
  cit.) 
  errs 
  in 
  attributing 
  the 
  genus 
  Echin- 
  

   arachnius 
  to 
  Leske, 
  for 
  he 
  was 
  himself 
  the 
  first 
  writer 
  to 
  use 
  

   the 
  name 
  as 
  a 
  generic 
  term. 
  He 
  includes 
  three 
  species 
  in 
  

   his 
  genus 
  — 
  placenta, 
  L., 
  and 
  Scutella 
  parma 
  and 
  lenticularis, 
  

   Lamk. 
  In 
  1841 
  Agassiz 
  restored 
  placenta 
  to 
  the 
  genus 
  

   Arachnoides 
  and 
  put 
  lenticularis 
  in 
  Scutel/ina, 
  so 
  that 
  parma 
  

   becomes 
  the 
  type 
  of 
  Echinarachnius. 
  As 
  placenta 
  is 
  the 
  only 
  

  

  