﻿364 
  

  

  PAL-BONTOLOGI 
  OF 
  [LLINOI8. 
  

  

  rim; 
  four 
  of 
  them 
  are 
  equal, 
  the 
  posterior 
  one 
  is 
  larger, 
  and 
  con- 
  

   fluent 
  with 
  the 
  anal 
  aperture. 
  Bydrospires 
  and 
  summit 
  plates 
  un- 
  

   known. 
  

  

  The 
  ornamentation 
  consists 
  in 
  fine 
  oonoentrio 
  lines 
  following 
  the 
  

   raJ 
  contour 
  of 
  the 
  plates. 
  

  

  Of 
  the 
  two 
  Bpeoimena 
  from 
  which 
  tin- 
  lesoribed, 
  01 
  

  

  nearly 
  perfect 
  and 
  larg< 
  t 
  than 
  the 
  other. 
  On 
  one 
  ride 
  ol 
  the 
  Bmallei 
  

   one 
  is 
  a 
  crushed 
  mass 
  of 
  b1< 
  nd< 
  t 
  arm-, 
  composed 
  of 
  pieces 
  of 
  about 
  

   equal 
  width 
  and 
  height, 
  which 
  possibly 
  may 
  be 
  some 
  of 
  the 
  pinnul 
  

  

  Pentremitidea 
  Americana 
  resembles 
  very 
  closely 
  Peal 
  

   Sehultee— 
  Pentremitidca 
  clavata, 
  Eth. 
  and 
  Car]..-, 
  bo 
  oloa 
  

   that 
  it 
  might 
  almost 
  be 
  taken 
  for 
  it; 
  the 
  latter, 
  however, 
  has 
  com- 
  

   paratively 
  longer 
  basals, 
  is 
  more 
  pentalobate, 
  has 
  wider 
  limbs, 
  with 
  

   decidedly 
  convex 
  sides 
  in 
  place 
  of 
  almost 
  straight 
  ones, 
  a: 
  am- 
  

  

  bulacra 
  extend 
  beyond 
  the 
  general 
  surfa. 
  

  

  Geological 
  position, 
  etc.: 
  In 
  the 
  upper 
  portion 
  of 
  the 
  Hamilton 
  

   group 
  in 
  the 
  Thunder 
  Bay 
  region 
  of 
  Northern 
  Michigan. 
  Ti. 
  

  

  arc 
  in 
  in 
  v 
  own 
  collection. 
  

  

  

  

  