﻿260 
  PALEONTOLOGY 
  OF 
  ILLINOIS. 
  

  

  important 
  oharaoter, 
  not 
  so 
  dearly 
  discernible 
  in 
  the 
  fragment 
  of 
  

   Bpine 
  upon 
  which 
  the 
  existence 
  of 
  the 
  genua 
  was 
  baaed, 
  of 
  the 
  back- 
  

   ward 
  curvature, 
  which 
  removes 
  it 
  from 
  the 
  Drepanacanthi. 
  with 
  which 
  

  

  an 
  some 
  resemblance 
  in 
  the 
  character 
  and 
  disposition 
  of 
  the 
  

   Longitudinal 
  ribs 
  and 
  tubercles 
  occupying 
  the 
  expoaed 
  parts. 
  Unfor- 
  

   tunately 
  the 
  entire 
  section 
  of 
  the 
  spine 
  is 
  not 
  preaerved, 
  so 
  thai 
  we 
  

   are 
  still 
  oninformed 
  in 
  regard 
  to 
  the 
  contour 
  of 
  the 
  posterior 
  face. 
  

   Specifically 
  allied 
  to 
  the 
  Kinderhook 
  Glymmatacantkui 
  Iri$hU, 
  Bi 
  

   .1. 
  and 
  \\\, 
  it 
  is 
  readily 
  distinguished 
  by 
  the 
  more 
  rapidly 
  tapering, 
  

   smaller, 
  transversely 
  elongate, 
  and 
  much 
  more 
  prominent 
  or 
  conical 
  

   tubercles, 
  which 
  are 
  also 
  more 
  closely 
  ranged 
  along 
  thi 
  - 
  . 
  and 
  

   more 
  widely 
  spaced 
  laterally 
  than 
  observed 
  in 
  the 
  unique 
  example 
  

   of 
  the 
  earlier 
  Bpecies 
  just 
  mentioned. 
  

  

  Geological 
  position 
  and 
  locality: 
  Keokuk 
  limestone; 
  Government 
  

   canal 
  excavations 
  around 
  the 
  Keokuk 
  rapids 
  on 
  tin 
  Mississippi, 
  

   above 
  Keokuk, 
  Iowa. 
  

  

  (il.VMMATACANTUUS 
  PETRODOIDKH. 
  St. 
  J. 
  and 
  \Y. 
  

   PL 
  XXV. 
  Fit. 
  J. 
  

  

  A 
  mere 
  fragment 
  of 
  an 
  iohthyodorulite, 
  hardly 
  a 
  centin 
  

   Bquare, 
  in 
  the 
  collection 
  of 
  Dr. 
  Bambaoh, 
  is 
  probably 
  referable 
  to 
  

   the 
  above 
  genu-. 
  The 
  superficial 
  ornamentation 
  ia 
  ao 
  well 
  preserved 
  

  

  enable 
  very 
  satisfactory 
  comparisons 
  with 
  other 
  spi 
  cies 
  of 
  the 
  

   90 
  to 
  show 
  its 
  distinctive 
  features 
  BO 
  fir 
  a- 
  tiny 
  depend 
  

  

  on 
  the 
  oharaoter 
  of 
  the 
  surface 
  ornamentation. 
  The 
  fragment 
  rep- 
  

  

  a 
  bit 
  from 
  the 
  lateral 
  wall.- 
  inolosing 
  the 
  pulp 
  cavity, 
  an.! 
  

  

  probably 
  pertained 
  to 
  a 
  Bpine 
  of 
  medium 
  m 
  longitudinal 
  

   costal 
  show 
  only 
  moderafc 
  convexity 
  with 
  the 
  usual 
  alongafc 
  

   In- 
  punots; 
  closely 
  arranged 
  along 
  their 
  creel 
  itrong 
  

   oonioa] 
  tuberolea 
  which 
  crowd 
  the 
  Burface, 
  and 
  which 
  ai 
  

   graven 
  with 
  sharp, 
  Btrong 
  carina 
  . 
  radiating 
  from 
  the 
  apex 
  and 
  < 
  ■ 
  

  

  -tried 
  d 
  at 
  the 
  base. 
  The 
  latter 
  character, 
  which, 
  on 
  account 
  of 
  the 
  

  

  resemblance 
  to 
  the 
  vertical 
  plication 
  of 
  the 
  oonee 
  of 
  / 
  

  

  nation, 
  also 
  offers 
  a 
  marked 
  and 
  tangible 
  

  

  contrast 
  with 
  the 
  tub. 
  rcular 
  ornamentation 
  observe.) 
  m 
  C01 
  

  

  with 
  thi 
  isl] 
  deaeribi 
  •! 
  i 
  ; 
  

  

  logical 
  j>nsiti<»i 
  „n,l 
  localitg 
  I 
  [meatoi 
  

  

  Illiii. 
  

  

  