﻿INTRODUCTORY. 
  

  

  61 
  

  

  DIAGRAM 
  ILLUSTRATING 
  THE 
  STRATIGRAPHICAL 
  DISTRIBUTION 
  AND 
  THE 
  

   RELATIONS 
  OF 
  THE 
  GENERA 
  OF 
  COCHLIODONTS. 
  

  

  -Kinderh 
  a 
  olr. 
  

  

  Besides 
  the 
  above 
  mentioned 
  Cochliodonts 
  and 
  Psammodonts, 
  a 
  

   considerable 
  number 
  of 
  heretofore 
  undescribed 
  forms, 
  pertaining 
  

   chiefly 
  to 
  Ichthyodorulites, 
  or 
  defensive 
  spines, 
  are 
  noticed, 
  being 
  

   acquisitions 
  acquired 
  since 
  the 
  publication 
  of 
  the 
  preceding 
  volume 
  

   of 
  the 
  Illinois 
  Geological 
  Survey. 
  As 
  in 
  connection 
  with 
  the 
  latter 
  

   work 
  the 
  authors 
  owe 
  acknowledgment 
  to 
  the 
  same 
  gentlemen, 
  who 
  

   have 
  not 
  only 
  contributed 
  material, 
  but 
  have 
  freely 
  shared 
  the 
  

   results 
  of 
  their 
  familiarity 
  with 
  the 
  objects 
  themselves, 
  and 
  the 
  in- 
  

   valuable 
  information 
  relating 
  to 
  their 
  stratigraphical 
  association 
  and 
  

   distribution, 
  so 
  that 
  we 
  feel 
  a 
  double 
  interest 
  with 
  them 
  as 
  con- 
  

   tributors 
  to 
  a 
  knowledge 
  of 
  these 
  early 
  vertebrates. 
  

  

  