﻿COCHLIODONTID^, 
  Owen. 
  

  

  Genus 
  PSEPHODUS, 
  Agassiz. 
  

  

  Psephodus, 
  Agassiz, 
  MSS., 
  1859, 
  etc. 
  

  

  The 
  genus 
  Psephodus 
  was 
  recognized 
  by 
  Professor 
  Agassiz 
  iu 
  1859, 
  

   by 
  whom 
  Cochliodus 
  magnus, 
  Ag., 
  of 
  the 
  Irish 
  Mountain 
  limestone, 
  

   was 
  regarded 
  as 
  the 
  typical 
  species. 
  This 
  determination 
  was 
  

   accepted 
  by 
  British 
  palaeichthyologists, 
  and 
  a 
  few 
  years 
  later, 
  1862, 
  

   it 
  was 
  authoritatively 
  published 
  by 
  Messrs. 
  J. 
  Morris 
  and 
  Gr. 
  E. 
  Eob- 
  

   erts, 
  in 
  the 
  Quat. 
  Journ. 
  of 
  the 
  (xeol. 
  Soc. 
  of 
  London, 
  XVIII, 
  p. 
  

   102. 
  At 
  a 
  subsequent 
  date, 
  1866, 
  Messrs. 
  Newberry 
  and 
  Worthen, 
  

   in 
  their 
  investigations 
  of 
  the 
  fossil 
  fishes 
  published 
  in 
  the 
  report 
  of 
  the 
  

   Illinois 
  Geological 
  Survey, 
  Vol. 
  2, 
  p. 
  92, 
  described 
  several 
  congeneric 
  

   species 
  from 
  the 
  American 
  Lower 
  Carboniferous 
  formations, 
  bowever, 
  

   evidently 
  overlooking 
  the 
  prior 
  published 
  conclusions 
  arrived 
  at 
  by 
  

   Professor 
  Agassiz, 
  as 
  they 
  distinctly 
  identify 
  the 
  type 
  species 
  of 
  

   Psephodus 
  with 
  the 
  American 
  species, 
  to 
  which 
  they 
  applied 
  the 
  gen- 
  

   eric 
  designation 
  Aspidodus. 
  In 
  regard 
  to 
  the 
  generic 
  identity 
  of 
  the 
  

   American 
  species 
  described 
  under 
  the 
  latter 
  designation, 
  as 
  also 
  

   those 
  additional 
  ones 
  herein 
  first 
  made 
  known, 
  with 
  Psephodus 
  mag- 
  

   nus, 
  Agass., 
  there 
  is 
  not 
  the 
  least 
  doubt. 
  

  

  In 
  the 
  present 
  work 
  the 
  results 
  of 
  the 
  attempts 
  made 
  to 
  identify 
  

   the 
  probable 
  complete 
  dentition 
  of 
  Psephodus 
  are 
  omitted, 
  only 
  such 
  

   forms 
  receiving 
  brief 
  diagnostic 
  notice, 
  the 
  relations 
  of 
  which 
  may 
  be 
  

   considered 
  as 
  even 
  more 
  than 
  probably 
  determined. 
  These 
  consist 
  

   of 
  two 
  distinct 
  forms 
  of 
  heavy, 
  more 
  or 
  less 
  spirally 
  in-rolled 
  trit- 
  

   urating 
  or 
  crushing 
  plates, 
  investing 
  the 
  median 
  region 
  of 
  the 
  rami 
  

   of 
  the 
  jaws: 
  

  

  

  