﻿3i 
  A. 
  F. 
  Foerste 
  — 
  Relations 
  of 
  the 
  

  

  notch 
  between 
  the 
  tips 
  of 
  the 
  posterior 
  ribs. 
  Instead 
  of 
  

   this, 
  the 
  posterior 
  end 
  of 
  the 
  axial 
  lobe 
  of 
  Platopolichas 
  

   is 
  still 
  wide 
  enough 
  to 
  embrace 
  the 
  notch. 
  The 
  cranidia 
  

   of 
  Platopolichas 
  have 
  no 
  resemblance 
  to 
  those 
  of 
  Acro- 
  

   lichas. 
  The 
  anterior 
  lateral 
  glabellar 
  lobes 
  are 
  not 
  dif- 
  

   ferentiated 
  from 
  the 
  second 
  pair 
  of 
  lobes 
  along 
  the 
  entire 
  

   length 
  of 
  the 
  intervening 
  line, 
  but 
  the 
  posterior 
  pair 
  of 
  

   lobes 
  is 
  distinctly 
  defined. 
  

  

  If 
  the 
  pygidia 
  have 
  not 
  been 
  incorrectly 
  associated 
  by 
  

   European 
  authors 
  with 
  the 
  cranidia 
  in 
  their 
  descrip- 
  

   tion 
  of 
  species, 
  then 
  such 
  cases 
  of 
  parallelism 
  occur 
  

   also 
  between 
  other 
  genera 
  of 
  Lichadidse. 
  This 
  greatly 
  

   increases 
  the 
  difficulty 
  of 
  grouping 
  species 
  into 
  genera. 
  

   Evidently 
  neither 
  the 
  cranidia 
  alone 
  nor 
  the 
  pygidia 
  

   alone 
  form 
  a 
  satisfactory 
  basis 
  for 
  the 
  erection 
  of 
  genera. 
  

   Both 
  must 
  be 
  taken 
  into 
  account. 
  

  

  9. 
  The 
  East 
  Baltic 
  genera 
  Hoplolichas 
  and 
  Conolichas. 
  

  

  The 
  East 
  Baltic 
  Ordovician 
  genera 
  Hoplolichas 
  and 
  

   Conolichas 
  are 
  of 
  interest 
  because 
  three 
  American 
  

   Lichads, 
  here 
  referred 
  to 
  Acrolichas, 
  originally 
  were 
  

   referred 
  to 
  these 
  East 
  Baltic 
  genera. 
  Using 
  the 
  East 
  

   Baltic 
  generic 
  names, 
  the 
  original 
  designations 
  of 
  these 
  

   species 
  were 
  Hoplolichas 
  robbinsi 
  Ulrich, 
  Hoplolichas 
  

   bicornis 
  Ulrich, 
  and 
  Conolichas 
  cornutus 
  Clarke. 
  

  

  The 
  genotype 
  of 
  Hoplolichas 
  is 
  Lichas 
  tricuspidatus 
  

   Beyrich 
  (PL 
  IV, 
  figs. 
  7 
  A, 
  B) 
  from 
  the 
  Eeval 
  formation 
  of 
  

   the 
  East 
  Baltic 
  provinces, 
  approximately 
  equivalent 
  to 
  

   our 
  upper 
  Stones 
  River 
  strata. 
  The 
  posterior 
  lateral 
  

   lobes 
  of 
  the 
  glabella 
  always 
  are 
  distinctly 
  defined, 
  but 
  the 
  

   line 
  of 
  separation 
  between 
  the 
  first 
  and 
  second 
  pairs 
  of 
  

   lobes 
  may 
  be 
  obsolete 
  in 
  some 
  specimens. 
  The 
  neck 
  ring 
  

   has 
  a 
  long 
  and 
  prominent 
  spine 
  projecting 
  from 
  its 
  pos- 
  

   terior 
  margin, 
  but 
  the 
  presence 
  of 
  this 
  spine 
  scarcely 
  can 
  

   be 
  regarded 
  as 
  a 
  generic 
  characteristic. 
  The 
  associated 
  

   pygidia 
  are 
  imperfectly 
  known, 
  but 
  it 
  is 
  certain 
  that 
  the 
  

   axial 
  lobe 
  does 
  not 
  terminate 
  posteriorly 
  in 
  a 
  point 
  reach- 
  

   ing 
  the 
  notch 
  between 
  the 
  tips 
  of 
  the 
  posterior 
  ribs. 
  

  

  The 
  genotype 
  of 
  Conolichas 
  is 
  Lichas 
  aequilobus 
  Stein- 
  

   hardt 
  (PL 
  IV, 
  figs. 
  8 
  A, 
  B), 
  from 
  the 
  Kegel 
  formation 
  of 
  

   the 
  East 
  Baltic 
  provinces, 
  corresponding 
  approximately 
  

   to 
  our 
  Trenton 
  strata. 
  In 
  this 
  genus, 
  also, 
  the 
  posterior 
  

   lateral 
  glabellar 
  lobes 
  are 
  distinctly 
  defined, 
  but 
  the 
  

  

  