﻿252 
  PALAEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  . 
  and 
  that 
  the 
  basals 
  in 
  the 
  Blastoids 
  generally 
  wan 
  mono- 
  

   cyclic 
  and 
  not 
  tricyclic. 
  This 
  seems 
  to 
  be 
  also 
  the 
  opinion 
  ..f 
  Bth- 
  

   eridge 
  and 
  Carpenter, 
  although 
  tiny 
  state 
  distinctly 
  that 
  they 
  wish 
  

   to 
  leave 
  the 
  question 
  for 
  farther 
  consideration. 
  

  

  HETr.KoM-iusMA. 
  Wachsmuth, 
  Nov. 
  gen. 
  

  

  The 
  form 
  under 
  consideration 
  is 
  closely 
  allied 
  to 
  C 
  . 
  and 
  

  

  approaches 
  Phanoschuma, 
  Ether, 
  aud 
  Carp. 
  The 
  he 
  lordingto 
  

  

  Ktheridge 
  and 
  Carpenter, 
  differs 
  from 
  r 
  in 
  the 
  following 
  

  

  points: 
  "In 
  the 
  partial 
  exposure 
  of 
  the 
  hydrospire 
  slits, 
  and 
  in 
  

   their 
  presence 
  in 
  the 
  anal 
  interradius, 
  as 
  well 
  as 
  in 
  the 
  four 
  o( 
  

   PhanoBchima 
  in 
  consequence 
  possesses 
  ten 
  gronpe 
  of 
  h\ 
  

   whilst 
  Codaster 
  has 
  only 
  eight. 
  Further 
  the 
  former 
  genua 
  

   tively 
  smaller 
  oral- 
  thin 
  the 
  latter, 
  and 
  it 
  may 
  .possess 
  outer 
  - 
  

   plates 
  to 
  the 
  ambulacra." 
  (Ann. 
  and 
  Mag. 
  Nat. 
  Hi-t.. 
  April, 
  

  

  127.) 
  

  

  Hetero8chitma 
  stands 
  intermediate 
  between 
  the 
  two 
  form-, 
  it 
  ag 
  

   in 
  the 
  above 
  characters 
  with 
  Pharuuekuma 
  except 
  that 
  it 
  has 
  hut 
  

   eight 
  groups 
  of 
  hydrospires 
  in 
  place 
  of 
  ten. 
  

  

  Admitting 
  that 
  the 
  ditference 
  in 
  the 
  number 
  of 
  hydrospiral 
  gi 
  

   alone 
  is 
  sufficient 
  for 
  a 
  separation 
  from 
  Coda$ter, 
  the 
  intermediate 
  

   form 
  must 
  be 
  placed 
  either 
  together 
  with 
  that 
  genus, 
  or 
  be 
  arrai 
  

  

  under 
  B 
  now 
  mime. 
  I 
  follow 
  the 
  latter 
  OOUrse, 
  as 
  I 
  the 
  

  

  structural 
  differences 
  in 
  the 
  oral 
  plates 
  as 
  important 
  as 
  the 
  numer- 
  

   ical 
  difference 
  in 
  the 
  bydrospires, 
  the 
  more 
  as 
  they 
  involve 
  other 
  

  

  important 
  structural 
  complications. 
  In 
  the 
  typical 
  form 
  of 
  I 
  

   including 
  the 
  more 
  flat-topped 
  with 
  small 
  

  

  plate- 
  cover 
  almost 
  the 
  who!.' 
  of 
  the 
  truncate 
  Upper 
  face 
  of 
  the 
  

  

  body, 
  ' 
  with 
  their 
  lateral 
  si; 
  inst 
  the 
  inflected 
  upper 
  

  

  part 
  of 
  the 
  liml.s. 
  The 
  oral 
  of 
  mon 
  

  

  mark 
  • 
  or 
  elevated 
  ridges, 
  which 
  occupy 
  nearly 
  the 
  full 
  width 
  

  

  of 
  the 
  holy. 
  To 
  both 
  are 
  placed 
  tl 
  i 
  

  

  -pin-, 
  all 
  located 
  within 
  the 
  limits 
  of 
  I 
  -mall 
  

  

  portions 
  of 
  them 
  b( 
  ing 
  continued 
  along 
  the 
  sides 
  of 
  the 
  limbs, 
  In 
  

   tl,,. 
  more 
  olavate 
  form 
  with 
  small 
  orals, 
  for 
  whiofa 
  I 
  propose 
  the 
  

   name 
  Hi 
  "''•> 
  only 
  i 
  (posed 
  to 
  new 
  ; 
  the 
  

  

  found 
  the 
  mouth; 
  tic 
  con- 
  

  

  I 
  portions, 
  which 
  underneath 
  i 
  t<> 
  the 
  two 
  inner 
  

  

  rlapp 
  d 
  by 
  the 
  • 
  ode 
  of 
  t* 
  is 
  limbs. 
  

  

  