﻿INVEETEBEATES. 
  337 
  

  

  Collected 
  by 
  A. 
  H. 
  Worthen 
  from 
  the 
  Chester 
  limestone 
  in 
  Monroe 
  

   and 
  Pope 
  counties. 
  

   No. 
  2,478, 
  Illinois 
  State 
  collection. 
  

  

  Abch^ocidaris 
  Edgarensis, 
  Sp. 
  nov. 
  

  

  PL 
  XXX, 
  Fig. 
  15. 
  a. 
  b. 
  c. 
  

  

  Primary 
  spines 
  long, 
  gradually 
  tapering, 
  cylindrical; 
  articulating 
  

   end 
  perforated 
  with 
  a 
  round 
  aperture, 
  and 
  enlarged 
  in 
  a 
  space 
  of 
  

   about 
  a 
  quarter 
  of 
  an 
  inch 
  into 
  a 
  strongly 
  striated 
  ring, 
  from 
  which 
  

   it 
  rapidly 
  decreases 
  above 
  to 
  its 
  normal 
  diameter 
  at 
  the 
  articu- 
  

   lating 
  extremity. 
  The 
  upper 
  portion 
  of 
  the 
  primary 
  spines 
  for 
  about 
  

   three-fourths 
  of 
  their 
  entire 
  length 
  are 
  rather 
  thickly 
  set 
  with 
  short 
  

   lateral 
  spinules, 
  that 
  project 
  upwards 
  towards 
  the 
  extremity 
  of 
  the 
  

   spine, 
  where 
  the 
  latter 
  terminates 
  in 
  a 
  mucronate 
  point. 
  

  

  Interambulacral 
  plates 
  hexagonal, 
  length 
  and 
  breadth 
  nearly 
  

   equal, 
  with 
  a 
  single 
  row 
  of 
  granules 
  on 
  the 
  rim 
  of 
  the 
  smaller 
  

   plates, 
  while 
  on 
  the 
  larger 
  ones 
  two 
  or 
  more 
  rows 
  of 
  small 
  granules 
  

   may 
  be 
  seen. 
  

  

  This 
  species 
  bears 
  some 
  resemblance 
  to 
  A. 
  mucronatus, 
  Meek 
  and 
  

   Worthen, 
  described 
  and 
  figured 
  in 
  Volume 
  2 
  of 
  these 
  reports, 
  page 
  

   295, 
  PI. 
  23, 
  fig. 
  3, 
  a. 
  b. 
  c. 
  That 
  species 
  was 
  obtained 
  from 
  the 
  

   Chester 
  limestone, 
  and 
  the 
  A. 
  Eclgarensc 
  may 
  be 
  readily 
  distin- 
  

   guished 
  from 
  that 
  by 
  its 
  shorter 
  and 
  more 
  numerous 
  spinules, 
  its 
  

   strongly 
  striated 
  ring, 
  and 
  the 
  less 
  robust 
  character 
  of 
  its 
  primary 
  

   spines. 
  

  

  Position 
  and 
  locality 
  : 
  Upper 
  Coal 
  Measures, 
  one 
  mile 
  east 
  of 
  Bald- 
  

   winsville, 
  Edgar 
  county, 
  111. 
  

  

  No. 
  2,447, 
  Illinois 
  State 
  collection. 
  

  

  Arceleocidaris 
  spino-clavatus, 
  Sp. 
  nov. 
  

  

  PI. 
  XXX, 
  fig. 
  14. 
  a, 
  b, 
  c, 
  d, 
  e, 
  and 
  Vol. 
  5, 
  PI. 
  XXIV. 
  fig. 
  13, 
  a, 
  b, 
  c, 
  d, 
  e 
  

  

  Primary 
  spines 
  rather 
  long, 
  moderately 
  stout, 
  cylindrical 
  at 
  the 
  

   base 
  and 
  gradually 
  increasing 
  in 
  diameter 
  toward 
  the 
  upper 
  ex- 
  

   tremity 
  to 
  twice 
  or 
  three 
  times 
  the 
  diameter 
  below, 
  and 
  then 
  rapidly 
  

   diminishing 
  to 
  an 
  obtuse 
  termination. 
  

  

  The 
  enlarged 
  upper 
  portions 
  of 
  the 
  spines 
  are 
  sometimes 
  subtri- 
  

  

  angular 
  in 
  section 
  and 
  thickly 
  covered 
  with 
  nodose 
  spinules, 
  which 
  

  

  are 
  longest 
  on 
  the 
  angles, 
  and 
  directed 
  upward 
  toward 
  the 
  apex 
  of 
  

   —22 
  

  

  