﻿270 
  PAL.KoXTOLOGT 
  OF 
  ILLINC! 
  

  

  1. 
  The 
  arms 
  are 
  Btont, 
  and 
  composed 
  of 
  rounded, 
  short, 
  m 
  arly 
  

   j. 
  mallei 
  plates, 
  that 
  give 
  off 
  delicate 
  pinnules 
  from 
  their 
  inner 
  mar- 
  

   gins. 
  The 
  npppei 
  part 
  of 
  the 
  ventral 
  tuhe 
  is 
  exposed 
  by 
  the 
  parti*] 
  

   removal 
  <>f 
  the 
  arms, 
  showing 
  that 
  this 
  organ 
  was 
  trumpet-shi 
  

   and 
  crowned 
  with 
  hea\y 
  hexagona] 
  plate.-, 
  prodoeed 
  at 
  V 
  

   into 
  rather 
  sharp 
  nodes, 
  while 
  below 
  the 
  plafa 
  thinner, 
  and 
  

  

  crossed 
  by 
  about 
  three 
  Bharp 
  ridges, 
  that 
  are 
  most 
  prominent 
  in 
  the 
  

   center 
  of 
  the 
  plate. 
  Similar 
  ridges 
  are 
  also 
  visible 
  on 
  the 
  margins 
  

   of 
  some 
  of 
  the 
  summit 
  plates. 
  Anal 
  plate- 
  unknown. 
  Column 
  

   round 
  and 
  rather 
  stout, 
  composed 
  of 
  thin, 
  even 
  plates. 
  Length 
  of 
  

   body 
  and 
  arras 
  5| 
  inches, 
  breadth 
  at 
  the 
  summit 
  of 
  the 
  ventral 
  

   tube 
  '2; 
  inches, 
  Length 
  of 
  column 
  7: 
  inc 
  

  

  This 
  magnificent 
  specimen 
  of 
  Poteriocrimu, 
  the 
  fin< 
  obtained 
  

  

  from 
  the 
  Keokuk 
  Limestone; 
  I 
  take 
  pleasure 
  in 
  dedicating 
  to 
  Mr. 
  

   I.. 
  V. 
  Cox, 
  of 
  Keokuk, 
  Iowa, 
  to 
  whom 
  it 
  belong-, 
  in 
  recognition 
  of 
  

   hi- 
  zeal 
  ami 
  untiling 
  industry 
  in 
  collecting 
  the 
  orinoids 
  and 
  : 
  

   of 
  that 
  vicinity. 
  

  

  itionand 
  locality: 
  Upper 
  part 
  of 
  the 
  Keokuk 
  Limestone, 
  Ham- 
  

   ilton, 
  111. 
  

  

  Mr. 
  L. 
  A. 
  Cox's 
  collection. 
  

  

  Pol 
  BBS 
  :. 
  Wort 
  hen. 
  

  

  PI. 
  XXVIII. 
  Fin. 
  8. 
  

   i.iry. 
  1»C. 
  

  

  Natural] 
  .5. 
  

  

  Body 
  small, 
  cup-shaped 
  below 
  the 
  summit 
  of 
  the 
  first 
  radial 
  

  

  plates. 
  Basalfl 
  Miiall 
  and 
  conceal- 
  d 
  by 
  the 
  first 
  joints 
  of 
  the 
  column. 
  

  

  Bubradial 
  plates 
  slightly 
  protuberant 
  from 
  the 
  depression 
  of 
  their 
  

   upper 
  angles, 
  curving 
  below 
  into 
  the 
  basal 
  concavity. 
  

  

  Radials 
  pentagonal, 
  about 
  once 
  and 
  a 
  half 
  as 
  wide 
  as 
  Lot 
  

  

  dual- 
  two 
  to 
  each 
  ray. 
  the 
  fust 
  quadrangular, 
  and 
  ti 
  1 
  the 
  

  

  same 
  form 
  as 
  the 
  radial-, 
  and 
  supporting 
  0O 
  their 
  Upper, 
  sloping 
  

  

  the 
  first 
  division 
  of 
  the 
  anna. 
  The 
  arms 
  after 
  the 
  first 
  I 
  

   ion 
  on 
  tl 
  ad 
  brachial 
  plate, 
  divide 
  again 
  on 
  the 
  Birth 
  to 
  the 
  

  

  ninth 
  plate, 
  beyond 
  which 
  they 
  continue 
  simple 
  to 
  their 
  extrem 
  

   making 
  four 
  arm- 
  to 
  each 
  ray. 
  vims 
  composed 
  of 
  slightly 
  « 
  

  

  formi 
  d 
  | 
  the 
  last 
  bifurcation, 
  but 
  

  

  prop 
  r 
  and 
  mOtf 
  ; 
  IB 
  their 
  an 
  

  

  givin 
  rales 
  alternately 
  from 
  their 
  longest 
  sides. 
  

  

  ■ 
  one 
  apparent!] 
  between 
  tw 
  sub- 
  

  

  