﻿32 
  A. 
  F. 
  Foerste 
  — 
  Relations 
  of 
  the 
  

  

  6. 
  American 
  species 
  of 
  Acrolichas 
  formerly 
  were 
  referred 
  to 
  the 
  

   European 
  genus 
  Amphilichas. 
  

  

  The 
  cranidium 
  of 
  Acrolichas 
  practically 
  is 
  identical 
  in 
  

   structure 
  with 
  that 
  of 
  Amphilichas, 
  a 
  genus 
  of 
  Lichads 
  

   from 
  the 
  Baltic 
  areas. 
  For 
  this 
  reason 
  Raymond 
  pro- 
  

   visionally 
  referred 
  Lichas 
  minganensis 
  to 
  his 
  genus 
  

   Amphilichas, 
  and 
  Slocom 
  later 
  placed 
  both 
  Amphilichas 
  

   clermontensis 
  and 
  Amphilichas 
  rhinoceras 
  in 
  that 
  genus. 
  

   Recently 
  Bassler, 
  in 
  his 
  Bibliographic 
  Index, 
  added 
  

   Lichas 
  bicornis, 
  L. 
  cucullus, 
  L. 
  jukesii, 
  L. 
  robbinsi, 
  and 
  

   L. 
  trentonensis 
  to 
  the 
  list 
  of 
  American 
  species 
  referred 
  

   to 
  Amphilichas, 
  thus 
  making 
  a 
  total 
  of 
  eight 
  species 
  

   then 
  listed 
  under 
  Amphilichas, 
  all 
  of 
  which 
  here 
  are 
  

   placed 
  under 
  Acrolichas. 
  

  

  The 
  name 
  Amphilichas 
  was 
  proposed 
  by 
  Professor 
  

   Percy 
  E. 
  Raymond, 
  in 
  1905, 
  for 
  the 
  group 
  of 
  species 
  

   Lichas 
  Icevis 
  Eichwald, 
  Lichas 
  dalecarlica 
  Angelin, 
  and 
  

   Lichas 
  holmi 
  Schmidt, 
  and 
  he 
  referred 
  to 
  the 
  first 
  of 
  

   these 
  species 
  as 
  the 
  type. 
  In 
  1910, 
  Raymond 
  compares 
  

   Lichas 
  minganensis 
  Billings 
  not 
  with 
  Lichas 
  Icevis 
  Bat 
  

   with 
  Lichas 
  lineatus 
  Angelin. 
  However, 
  in 
  this 
  case 
  ffi 
  : 
  i 
  

   term 
  Lichas 
  lineatus 
  refers 
  to 
  the 
  same 
  species 
  as 
  tha 
  

   described 
  by 
  Schmidt 
  under 
  Lichas 
  Icevis, 
  as 
  shown 
  by 
  

   a 
  footnote 
  (Ann. 
  Carnegie 
  Museum, 
  vol. 
  7, 
  p. 
  73) 
  in 
  

   which 
  the 
  Revision 
  der 
  Ostbaltischen 
  Silurischen 
  Tri- 
  

   lobiten, 
  II, 
  1885, 
  pi. 
  6, 
  fig. 
  5, 
  1885, 
  by 
  Schmidt, 
  is 
  cited 
  

   as 
  giving 
  information 
  regarding 
  Lichas 
  lineatus. 
  This 
  

   figure 
  5, 
  however, 
  consists 
  of 
  three 
  views 
  of 
  a 
  cephalon 
  

   described 
  by 
  Schmidt 
  under 
  Lichas 
  loevis. 
  Evidently 
  it 
  

   is 
  the 
  East 
  Baltic 
  specimen 
  (PI. 
  IV, 
  fig. 
  11A, 
  in 
  the 
  

   present 
  paper), 
  and 
  not 
  the 
  Scandinavian 
  form 
  (PL 
  IV, 
  

   figs. 
  12 
  A, 
  B), 
  which 
  is 
  the 
  genotype. 
  

  

  In 
  structure 
  the 
  cranidia 
  of 
  Acrolichas 
  and 
  Amphi- 
  

   lichas 
  are 
  practically 
  identical, 
  offering 
  an 
  excellent 
  

   illustration 
  of 
  parallelism 
  of 
  structures 
  in 
  different 
  

   genera. 
  The 
  pygidia, 
  on 
  the 
  contrary, 
  are 
  quite 
  dis- 
  

   similar. 
  In 
  the 
  pygidia 
  of 
  typical 
  Amphilichas 
  the 
  axial 
  

   lobe 
  does 
  not 
  narrow 
  posteriorly 
  to 
  a 
  point 
  terminating 
  

   at 
  the 
  notch 
  between 
  the 
  free 
  tips 
  of 
  the 
  posterior 
  pair 
  

   of 
  ribs, 
  as 
  in 
  Acrolichas. 
  In 
  the 
  pygidium 
  associated 
  

   by 
  Schmidt 
  with 
  the 
  genotype 
  of 
  Amphilichas 
  (PI. 
  IV, 
  

   fig. 
  11B, 
  in 
  the 
  present 
  paper) 
  the 
  axial 
  lobe 
  narrows 
  

   posteriorly 
  for 
  about 
  half 
  the 
  length 
  of 
  the 
  pygidium 
  

  

  