﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  199 
  

  

  proved 
  to 
  belong 
  to 
  the 
  form 
  represented 
  in 
  figures 
  8, 
  9 
  and 
  

   10, 
  the 
  difference 
  between 
  the 
  New 
  York 
  and 
  western 
  speci- 
  

   mens 
  would 
  be 
  still 
  more 
  marked. 
  The 
  individuals 
  reached 
  a 
  

   large 
  size, 
  as 
  is 
  shown 
  by 
  a 
  fragment 
  of 
  one 
  of 
  the 
  thoracic 
  

   segments, 
  having 
  a 
  width 
  of 
  nearly 
  120 
  mm. 
  

  

  Lichas 
  sp. 
  f 
  

  

  Plate 
  34, 
  Fig. 
  12. 
  

  

  The 
  fragment 
  figured 
  is 
  apparently 
  the 
  frontal 
  extension 
  of 
  

   the 
  border 
  of 
  the 
  glabella 
  of 
  a 
  species 
  of 
  Lichas, 
  correspond- 
  

   ing 
  to 
  what 
  is 
  shown 
  in 
  figure 
  la 
  of 
  plate 
  70, 
  vol. 
  ii, 
  Pal. 
  N. 
  Y. 
  

   It 
  is 
  probable 
  that 
  this 
  belongs 
  to 
  the 
  form 
  of 
  which 
  the 
  

   pygidia 
  are 
  represented 
  in 
  figures 
  8, 
  9 
  and 
  10, 
  of 
  the 
  same 
  

   plate. 
  

  

  Lichas 
  emarginatus 
  n. 
  sp. 
  

  

  Lichas 
  breviceps 
  ? 
  Hall. 
  20th 
  Rep. 
  St. 
  Cab. 
  Nat. 
  Hist., 
  p. 
  334, 
  pi. 
  21, 
  figs. 
  12-14. 
  

   1867. 
  Rev. 
  Edit., 
  p. 
  424. 
  [1870.] 
  

  

  A 
  comparison 
  of 
  this 
  form 
  with 
  L. 
  breviceps 
  shows 
  that 
  the 
  

   lateral 
  lobes 
  of 
  the 
  glabella 
  are 
  larger, 
  and 
  the 
  eye 
  tubercle 
  

   smaller. 
  The 
  axial 
  lobe 
  of 
  the 
  pygidium 
  is 
  more 
  prominent 
  

   and 
  longer, 
  marked 
  by 
  four 
  annulations 
  in 
  the 
  anterior 
  por- 
  

   tion, 
  and 
  is 
  gradually 
  narrowed 
  posteriorly, 
  having 
  a 
  dis- 
  

   tinct 
  conical 
  form, 
  with 
  no 
  expansion 
  into 
  the 
  posterior 
  border 
  

   as 
  in 
  L. 
  breviceps. 
  The 
  lateral 
  lobes 
  have 
  the 
  articulations 
  more 
  

   prolonged 
  and 
  bent 
  more 
  directly 
  backward. 
  The 
  pygidium 
  

   is 
  also 
  emarginate 
  behind, 
  while 
  in 
  L. 
  breviceps 
  from 
  Wal- 
  

   dron 
  it 
  is 
  continuous. 
  

  

  It 
  becomes 
  necessary, 
  therefore, 
  to 
  propose 
  a 
  name 
  for 
  the 
  

   Wisconsin 
  specimens 
  which 
  have 
  been 
  referred 
  to 
  L. 
  brevi- 
  

   ceps 
  f 
  . 
  

  

  This 
  species 
  may 
  be 
  compared 
  with 
  L. 
  scabra 
  of 
  Beyrich, 
  

   and 
  L. 
  avis 
  of 
  Barrande, 
  but 
  the 
  lateral 
  articulations 
  of 
  the 
  

   pygidium 
  are 
  much 
  shorter 
  in 
  this 
  species. 
  

  

  