﻿S16 
  PALJEONTOLOGT 
  OF 
  ILLINOIS. 
  

  

  A.OA88IZ00BIHUB 
  HEMIsnir.IUcrs. 
  Worthcii. 
  

   PL 
  XXIX. 
  lie 
  7. 
  

  

  AaattiMOcriitUM 
  hemitpl 
  

  

  Hull. 
  -tin 
  No. 
  l. 
  "f 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  Blstorr. 
  i 
  

  

  Body 
  small, 
  bowl-shaped, 
  or 
  hemispherical 
  in 
  outline, 
  about 
  once 
  

  

  and 
  a 
  half 
  a- 
  wide 
  as 
  high 
  to 
  the 
  summit 
  of 
  the 
  radial 
  - 
  unded 
  

  

  at 
  the 
  base, 
  and 
  composed 
  of 
  massive, 
  protuberant 
  pi: 
  

  

  Basals 
  small, 
  projecting 
  hut 
  slightly 
  below 
  the 
  Bubradials, 
  forming 
  

   a 
  little 
  pentagonal 
  star. 
  No 
  columnar 
  facet 
  is 
  visible. 
  

  

  Bubradials 
  a 
  little 
  longer 
  than 
  wide, 
  strongly 
  protuberant, 
  three 
  

   of 
  them 
  pentagonal, 
  and 
  two 
  on 
  the 
  posterior 
  side 
  hexagonal. 
  

  

  Badials 
  pentagonal, 
  three 
  of 
  them 
  rather 
  more 
  than 
  one< 
  and 
  a 
  

   half 
  as 
  wide 
  as 
  long, 
  the 
  two 
  on 
  the 
  posterior 
  side 
  rather 
  narrower 
  

   than 
  the 
  others, 
  and 
  all 
  truncated 
  squarely 
  across 
  their 
  summits 
  for 
  

   the 
  reception 
  of 
  the 
  hrachials. 
  Sutures 
  between 
  all 
  the 
  plates 
  of 
  the 
  

   body 
  distinct. 
  

  

  Brachials 
  as 
  wide 
  below 
  as 
  the 
  radials, 
  hut 
  Btrongly 
  constricted 
  

  

  and 
  Sharply 
  angular 
  above, 
  where 
  they 
  give 
  support 
  to 
  the 
  two 
  di- 
  

   visions 
  of 
  the 
  rays. 
  The 
  arm-plates 
  attach, 
  d 
  are 
  three 
  in 
  numb 
  

   the 
  first 
  nearly 
  twice 
  as 
  Long 
  as 
  the 
  succeeding 
  ones, 
  and 
  all 
  quad- 
  

   rangular 
  in 
  form. 
  . 
  

   Pour 
  anal 
  plates 
  are 
  visible, 
  the 
  first 
  is 
  protuberant, 
  pentangular, 
  

  

  aboul 
  half 
  as 
  large 
  as 
  the 
  largest 
  radiaK 
  and 
  n 
  an 
  ly 
  upon 
  

  

  the 
  truncated 
  apper 
  margin 
  of 
  the 
  right 
  posterior 
  Bubradial 
  and 
  m 
  

   tii. 
  left 
  side 
  of 
  the 
  right 
  posterior 
  radial. 
  Tl 
  1 
  anal 
  is 
  al 
  

  

  half 
  as 
  large 
  as 
  the 
  first, 
  longer 
  than 
  wide, 
  and 
  D 
  the 
  up] 
  

  

  margin 
  "f 
  the 
  left 
  Bubradial. 
  The 
  other 
  anals 
  are 
  smaller; 
  the 
  third 
  

  

  teste 
  between 
  the 
  first 
  and 
  BeOOnd, 
  and 
  the 
  fourth 
  on 
  the 
  summit 
  of 
  

  

  the 
  -.<oiid. 
  Column 
  unknown. 
  

  

  logical 
  position 
  and 
  lotaUt*: 
  Chester 
  lim. 
  landolph 
  county. 
  

  

  Qlirj 
  

   No. 
  2,461, 
  Illinois 
  state 
  ooUeotion. 
  

  

  