﻿INVEETEBEATES. 
  313 
  

  

  Genus 
  DICHOCKLNUS, 
  Munster. 
  

   Dichocrinus 
  Hamiltonensis, 
  Worthen. 
  

  

  PI. 
  XX 
  VII., 
  Fig. 
  10. 
  

  

  Dichocrinus 
  Hamiltonensis, 
  Worthen. 
  February, 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  35. 
  

  

  Body 
  small, 
  length 
  and 
  breadth 
  apparently 
  about 
  equal, 
  though 
  

   from 
  the 
  crushed 
  condition 
  of 
  the 
  body 
  plates 
  the 
  exact 
  proportions 
  

   of 
  the 
  body 
  can 
  not 
  be 
  accurately 
  determined. 
  Basals 
  about 
  half 
  

   as 
  long 
  as 
  the 
  radials, 
  forming 
  by 
  themselves 
  a 
  low, 
  shallow 
  cup. 
  

  

  Eadials 
  quadrangular, 
  nearly 
  once 
  and 
  a 
  half 
  as 
  long 
  as 
  wide, 
  

   with 
  a 
  narrow, 
  articulating 
  scar 
  at 
  the 
  summit 
  for 
  the 
  reception 
  of 
  

   the 
  brachial 
  series. 
  

  

  Brachials 
  three, 
  the 
  last 
  one 
  longer 
  than 
  those 
  below, 
  and 
  sup- 
  

   porting 
  on 
  its 
  upper 
  sloping 
  sides 
  the 
  first 
  arm 
  plates. 
  

  

  Arms 
  two 
  to 
  each 
  ray, 
  as 
  far 
  as 
  can 
  be 
  seen 
  in 
  the 
  specimen 
  

   before 
  me, 
  composed 
  of 
  short, 
  wedge-shaped 
  pieces, 
  rounded 
  ex- 
  

   teriorly, 
  and 
  giving 
  off 
  from 
  their 
  longest 
  sides 
  rather 
  strong 
  

   pinnules. 
  

  

  Column 
  unknown. 
  

  

  This 
  species 
  is 
  nearly 
  related 
  to 
  D. 
  ficus, 
  of 
  Lyon 
  and 
  Casseday, 
  

   but 
  differs 
  from 
  that 
  in 
  the 
  shorter 
  form 
  of 
  the 
  body 
  and 
  in 
  the 
  

   number 
  of 
  its 
  brachial 
  pieces, 
  which 
  in 
  their 
  species 
  is 
  only 
  two 
  to 
  

   each 
  ray. 
  

  

  Position 
  and 
  locality: 
  Upper 
  part 
  of 
  the 
  Keokuk 
  limestone, 
  Ham- 
  

   ilton, 
  111. 
  

  

  No. 
  257 
  of 
  Mr. 
  L. 
  A 
  Cox's 
  collection. 
  

  

  Dichocrinus 
  Coxanus, 
  Worthen. 
  

  

  PL 
  XXVII, 
  Fig. 
  7. 
  

   Dichocrinus 
  Coxanus, 
  Woethen, 
  February, 
  1882. 
  

   Bulletin 
  No. 
  1 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  35. 
  

  

  Body 
  small, 
  ovate 
  in 
  outline, 
  pointed 
  at 
  the 
  base 
  and 
  contracted 
  

   at 
  the 
  summit 
  of 
  the 
  radial 
  series, 
  so 
  that 
  its 
  greatest 
  diameter 
  is 
  

   near 
  the 
  base 
  of 
  the 
  radial 
  plates. 
  

  

  Basal 
  plates 
  nearly 
  three 
  -fourths 
  as 
  long 
  as 
  the 
  radials, 
  forming 
  

   by 
  themselves 
  a 
  rather 
  deep 
  cup. 
  

  

  