﻿IV 
  

  

  In 
  the 
  investigation 
  of 
  fossil 
  echinoids, 
  I 
  was 
  so 
  fortunate 
  as 
  to 
  

   secure 
  the 
  assistance 
  of 
  S. 
  A. 
  Miller, 
  Esq., 
  of 
  Cincinnati, 
  whose 
  

   familiarity 
  with 
  that 
  class 
  of 
  organism 
  renders 
  his 
  determinations 
  

   of 
  more 
  than 
  ordinary 
  value, 
  and 
  his 
  work 
  has 
  resulted 
  in 
  the 
  

   satisfactory 
  elucidation 
  of 
  some 
  very 
  difficult 
  and 
  rather 
  unsatisfac- 
  

   tory 
  material. 
  

  

  The 
  illustrations 
  for 
  this 
  volume 
  were 
  mostly 
  drawn 
  by 
  Mr. 
  

   Charles 
  K. 
  Worthen, 
  and 
  are 
  faithful 
  reproductions 
  of 
  the 
  original 
  

   specimens; 
  and 
  the 
  plates 
  have 
  been 
  engraved 
  and 
  printed 
  by 
  

   Messrs. 
  Julius 
  Mayer 
  & 
  Co., 
  of 
  Boston, 
  in 
  their 
  usual 
  excellent 
  

   style. 
  

  

  One 
  hundred 
  and 
  sixty-live 
  plates 
  of 
  fossils 
  have 
  been 
  published 
  

   in 
  the 
  preceding 
  volumes 
  of 
  the 
  Geological 
  Survey 
  of 
  Illinois, 
  which, 
  

   with 
  those 
  contained 
  in 
  the 
  present 
  volume, 
  brings 
  the 
  aggregate 
  

   number 
  now 
  published 
  up 
  to 
  one 
  hundred 
  and 
  ninety-six. 
  nearly 
  all 
  

   of 
  which 
  have 
  been 
  devoted 
  to 
  the 
  illustration 
  of 
  species 
  new 
  to 
  

   science, 
  and 
  mainly 
  obtained 
  in 
  prosecuting 
  the 
  held 
  work 
  of 
  the 
  

   geological 
  survey, 
  from 
  formations 
  existing 
  within 
  the 
  borders 
  of 
  the 
  

   State. 
  

  

  The 
  work, 
  however, 
  is 
  by 
  no 
  means 
  complete, 
  and 
  at 
  least 
  two 
  

   volumes 
  more, 
  illustrated 
  by 
  forty 
  to 
  fifty 
  plates 
  each, 
  would 
  be 
  re- 
  

   quired 
  to 
  complete 
  the 
  paleontology 
  of 
  the 
  State 
  in 
  the 
  manner 
  

   originally 
  contemplated. 
  These 
  volumes 
  should 
  also 
  include 
  such 
  

   economical 
  results 
  as 
  may 
  be 
  obtained 
  in 
  the 
  meantime 
  by 
  future 
  

   investigations. 
  

  

  Nothing 
  further 
  can 
  be 
  done 
  in 
  this 
  direction, 
  however, 
  until 
  pro- 
  

   vision 
  is 
  made 
  for 
  it 
  by 
  a 
  special 
  act 
  of 
  the 
  General 
  Assembly, 
  and 
  

   it 
  remains 
  for 
  the 
  legislative 
  authorities 
  to 
  determine 
  whctln 
  r 
  the 
  

   work 
  shall 
  be 
  continued 
  and 
  eventually 
  completed, 
  in 
  accordance 
  

   with 
  the 
  original 
  plan, 
  or 
  cease 
  with 
  the 
  publication 
  of 
  the 
  presenl 
  

   volume. 
  

  

  A. 
  II. 
  WORTHEN, 
  

  

  