﻿L6 
  A. 
  F. 
  Foerste 
  — 
  Relations 
  of 
  the 
  

  

  Richmond, 
  both 
  in 
  Ohio 
  and 
  Indiana. 
  Although 
  the 
  

   pygidia 
  from 
  both 
  horizons 
  are 
  characterized 
  by 
  short, 
  

   rounded 
  free 
  tips 
  at 
  the 
  end 
  of 
  the 
  ribs, 
  the 
  granules 
  on 
  

   the 
  surface 
  of 
  the 
  Liberty 
  specimens 
  are 
  coarser, 
  and 
  

   the 
  accompanying 
  transverse 
  narrow 
  ridges 
  are 
  bolder 
  

   than 
  in 
  the 
  AYaynesville 
  type, 
  so 
  that 
  the 
  specimens 
  

   from 
  the 
  Liberty 
  division 
  may 
  represent 
  an 
  undescribed 
  

   species. 
  Finally, 
  pygidia 
  of 
  the 
  same 
  general 
  type 
  occur 
  

   also 
  in 
  some 
  part 
  of 
  the 
  section 
  at 
  Richmond, 
  Indiana, 
  

   a 
  fragment, 
  including 
  all 
  except 
  the 
  anterior 
  pair 
  of 
  

   ribs, 
  occurring 
  in 
  the 
  Misener 
  collection. 
  

  

  Three 
  species 
  of 
  Acrolichas 
  are 
  known 
  from 
  the 
  

   Maquoketa 
  member 
  of 
  the 
  Richmond, 
  in 
  the 
  Missis- 
  

   sippi 
  valley. 
  Acrolichas 
  bicornis, 
  PL 
  II, 
  fig. 
  3, 
  from 
  

   Minnesota, 
  and 
  Acrolichas 
  rhinoceras, 
  PI. 
  II, 
  fig. 
  4, 
  from 
  

   Iowa, 
  have 
  the 
  glabella 
  ornamented 
  with 
  slender 
  spinose 
  

   extensions. 
  Acrolichas 
  clermontensis, 
  PL 
  II, 
  fig. 
  7, 
  from 
  

   Iowa, 
  is 
  characterized 
  by 
  the 
  rapid 
  widening 
  of 
  the 
  

   median 
  lobe 
  of 
  the 
  glabella 
  toward 
  the 
  front. 
  

  

  16. 
  Possible 
  occurrence 
  of 
  Acrolichas 
  in 
  Baltic 
  areas 
  of 
  Europe. 
  

  

  Since 
  at 
  present 
  in 
  America 
  only 
  pygidia 
  having 
  a 
  

   median 
  lobe 
  terminating 
  posteriorly 
  in 
  an 
  acute 
  point 
  

   are 
  known 
  definitely 
  to 
  be 
  associated 
  with 
  glabella? 
  re- 
  

   sembling 
  Amphilichas, 
  it 
  is 
  natural 
  to 
  assume 
  that 
  simi- 
  

   lar 
  associations 
  are 
  to 
  be 
  expected 
  in 
  typical 
  species 
  of 
  

   Amphilichas 
  in 
  the 
  Baltic 
  areas 
  of 
  northwestern 
  Europe. 
  

   Such 
  pygidia 
  might 
  be 
  sought 
  in 
  the 
  forms 
  associated 
  by 
  

   Schmidt 
  with 
  the 
  glabella? 
  of 
  Metalichas 
  cicatricosa 
  

   Loven 
  and 
  Metalichas 
  St. 
  Mathicc 
  Schmidt. 
  Neither 
  of 
  

   these 
  pygidia, 
  however, 
  is 
  sufficiently 
  similar 
  to 
  that 
  of 
  

   Acrolichas 
  to 
  demand 
  its 
  association 
  with 
  Amphilichas, 
  

   on 
  the 
  supposition 
  that 
  Acrolichas 
  is 
  identical 
  with 
  

   Amphilichas. 
  

  

  In 
  Metalichas 
  cicatricosa 
  the 
  furrow 
  limiting 
  the 
  pos- 
  

   terior 
  border 
  of 
  the 
  second 
  axial 
  ring 
  is 
  indistinct 
  medi- 
  

   ally, 
  instead 
  of 
  at 
  the 
  two 
  ends. 
  In 
  Metalichas 
  St. 
  

   Mathice, 
  the 
  furrows 
  traversing 
  the 
  lateral 
  ribs 
  length- 
  

   wise 
  terminate 
  at 
  the 
  angles 
  between 
  the 
  free 
  tips 
  of 
  

   these 
  ribs, 
  a 
  feature 
  unknown 
  not 
  only 
  in 
  Acrolichas 
  but 
  

   also 
  in 
  all 
  other 
  described 
  lichacls. 
  

  

  The 
  mere 
  presence 
  of 
  a 
  pointed 
  posterior 
  termination 
  

   of 
  the 
  axial 
  lobe 
  is 
  not 
  sufficient 
  to 
  stamp 
  a 
  pygidium 
  as 
  

   belonging 
  to 
  Acrolichas 
  or 
  Amphilichas. 
  The 
  tendency 
  

  

  