﻿INVERTEBRATES. 
  307 
  

  

  Primary 
  radials 
  three, 
  the 
  first 
  comparatively 
  large, 
  hexagonal 
  or 
  

   heptagonal, 
  the 
  succeeding 
  ones 
  small, 
  one 
  quadrangular 
  and 
  the 
  

   other 
  subtriangular, 
  supporting 
  on 
  its 
  upper 
  angles 
  the 
  secondary 
  

   radial 
  series. 
  

  

  Secondary 
  radials 
  two, 
  the 
  first 
  quadrangular 
  and 
  the 
  second 
  

   pentangular, 
  supporting 
  above 
  the 
  two 
  divisions 
  of 
  the 
  arms, 
  giving 
  

   four 
  arms 
  to 
  each 
  ray. 
  

  

  The 
  two 
  first 
  arm 
  plates 
  are 
  nearly 
  quadrangular, 
  and 
  longer 
  than 
  

   those 
  above. 
  The 
  third 
  and 
  fourth 
  are 
  nearly 
  triangular, 
  and 
  are 
  

   succeeded 
  by 
  a 
  double 
  series 
  of 
  slightly 
  interlocking 
  plates 
  that 
  

   spread 
  out 
  towards 
  their 
  extremities 
  in 
  the 
  manner 
  peculiar 
  to 
  this 
  

   genus. 
  

  

  Interradials 
  three, 
  the 
  first 
  about 
  twice 
  as 
  large 
  as 
  the 
  succeeding 
  

   ones. 
  Anal 
  series 
  unknown. 
  

  

  Column 
  at 
  its 
  junction 
  with 
  the 
  body 
  composed 
  of 
  thick, 
  round 
  

   joints 
  that, 
  a 
  short 
  distance 
  below, 
  are 
  separated 
  by 
  thinner 
  ones 
  

   arranged 
  alternately. 
  

  

  Surface 
  of 
  the 
  body 
  plates 
  finely 
  granulose, 
  with 
  a 
  slightly 
  elevated 
  

   ridge 
  crossing 
  the 
  plates, 
  and 
  extending 
  to 
  the 
  top 
  of 
  the 
  secondary 
  

   series. 
  

  

  This 
  species, 
  minus 
  the 
  arms, 
  closely 
  resembles 
  Batocrlnus 
  caroli 
  

   (Hall's 
  sp.) 
  from 
  the 
  same 
  beds, 
  but 
  differs 
  in 
  the 
  number 
  and 
  

   structure 
  of 
  the 
  arms, 
  that 
  having 
  but 
  sixteen 
  while 
  this 
  has 
  

   twenty. 
  

  

  Position 
  and 
  locality: 
  Warsaw 
  beds 
  of 
  the 
  St. 
  Louis 
  group, 
  War- 
  

   saw, 
  ill. 
  

  

  No. 
  2,459, 
  Illinois 
  State 
  collection. 
  

  

  Genus 
  ONYCHOCRI^TUS, 
  l. 
  and 
  C. 
  

  

  Onychoceinus 
  distensus, 
  Worthen. 
  

  

  PI. 
  XXIX, 
  Fig. 
  5. 
  

  

  Onychocrinus 
  distensus, 
  Woethen, 
  February, 
  1882. 
  

  

  Bulletin 
  No. 
  1, 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  31. 
  

  

  Body 
  of 
  medium 
  size, 
  composed 
  of 
  smooth, 
  massive 
  plates. 
  

   Basals 
  concealed 
  by 
  the 
  column. 
  

  

  Subradials 
  on 
  the 
  anterior 
  side 
  sharply 
  angular 
  beyond 
  the 
  col- 
  

   umnar 
  facet, 
  forming 
  a 
  low, 
  pentagonal 
  cup. 
  

  

  Radials 
  five, 
  the 
  first 
  pentagonal, 
  about 
  one-fourth 
  wider 
  than 
  

  

  