﻿American 
  Ordovician 
  Lichadidce. 
  L3 
  

  

  two 
  additional 
  ones 
  being 
  presented 
  by 
  the 
  present 
  writer 
  

   in 
  the 
  Ottawa 
  Naturalist, 
  in 
  1917 
  (PL 
  6, 
  figs. 
  26 
  A, 
  B). 
  

  

  Lichas 
  cuculhis 
  apparently 
  has 
  a 
  very 
  extensive 
  geo- 
  

   graphical 
  range. 
  In 
  the 
  Kimmswick 
  limestone 
  it 
  ranges 
  

   from 
  Alexander 
  county, 
  at 
  the 
  southern 
  end 
  of 
  Illinois, 
  

   northward 
  to 
  various 
  localities 
  in 
  Jefferson 
  county, 
  Mis- 
  

   souri; 
  Calhoun 
  county, 
  Illinois 
  (PL 
  I, 
  fig. 
  ID, 
  G) 
  ; 
  and 
  

   Kails 
  county, 
  Missouri 
  (PL 
  I, 
  figs. 
  1C, 
  F). 
  In 
  the 
  

   Prosser 
  limestone 
  it 
  is 
  known 
  at 
  Wykoff 
  in 
  Minnesota. 
  

   In 
  strata 
  regarded 
  as 
  of 
  Black 
  River 
  age, 
  it 
  occurs 
  at 
  

   Janesville, 
  Wisconsin, 
  and 
  on 
  Lake 
  Winnipeg, 
  in 
  Canada. 
  

   In 
  the 
  collection 
  of 
  James 
  E. 
  Narraway, 
  of 
  Ottawa, 
  Can- 
  

   ada, 
  both 
  cranidia 
  and 
  pygidia 
  occur, 
  from 
  the 
  Trenton 
  

   of 
  Hull, 
  immediately 
  across 
  the 
  river 
  from 
  Ottawa 
  (PL 
  

   I, 
  figs. 
  1A, 
  B, 
  E). 
  Lichas 
  is 
  listed 
  also 
  from 
  1 
  'Original, 
  

   nearly 
  50 
  miles 
  east 
  of 
  Ottawa, 
  and 
  from 
  the 
  east 
  end 
  of 
  

   Seche 
  Bay, 
  in 
  Mansfield 
  township, 
  about 
  50 
  miles 
  north- 
  

   west 
  of 
  Ottawa. 
  As 
  far 
  as 
  known 
  Lichas 
  trentonensis 
  

   does 
  not 
  occur 
  north 
  of 
  the 
  Prontenac 
  axis, 
  in 
  Canada, 
  so 
  

   that 
  these 
  citations 
  of 
  Lichas 
  from 
  POriginal 
  and 
  Seche 
  

   Bay 
  may 
  belong 
  to 
  Lichas 
  cucullus. 
  

  

  Considering 
  the 
  great 
  geographical 
  range 
  of 
  Acro- 
  

   lichas 
  cucullus, 
  and 
  its 
  occurrence 
  apparently 
  at 
  several 
  

   distinct 
  horizons, 
  it 
  is 
  not 
  unlikely 
  that 
  eventually, 
  when 
  

   the 
  associated 
  cranidia 
  and 
  pygidia 
  become 
  better 
  known, 
  

   several 
  species 
  will 
  be 
  differentiated 
  among 
  the 
  speci- 
  

   mens 
  now 
  referred 
  to 
  the 
  single 
  species 
  cucullus. 
  Dif- 
  

   ferences 
  are 
  noted 
  more 
  frequently 
  among 
  the 
  pygidia, 
  of 
  

   the 
  forms 
  here 
  discussed, 
  than 
  among 
  the 
  cranidia. 
  For 
  

   instance, 
  in 
  the 
  pygidium 
  from 
  the 
  Kimmswick 
  on 
  San- 
  

   ders 
  Branch, 
  in 
  Ralls 
  county, 
  Missouri 
  (PL 
  I, 
  ^g. 
  IF), 
  

   provisionally 
  regarded 
  as 
  typical 
  of 
  the 
  species, 
  the 
  free 
  

   tips 
  of 
  the 
  ribs 
  are 
  more 
  pointed 
  than 
  in 
  the 
  pygidium 
  

   from 
  Hull, 
  in 
  Canada 
  (PL 
  I, 
  fig. 
  IE). 
  

  

  In 
  the 
  Richmond 
  on 
  the 
  eastern 
  shore 
  of 
  Little 
  Bay 
  de 
  

   Noquette, 
  in 
  Northern 
  Michigan, 
  a 
  cranidium 
  was 
  found 
  

   (Ottawa 
  Naturalist, 
  31, 
  PL 
  6, 
  figs. 
  27A, 
  B, 
  1917) 
  which 
  

   could 
  not 
  be 
  distinguished 
  from 
  the 
  type 
  of 
  Acrolichas 
  

   cucullus. 
  The 
  pygidium, 
  if 
  known, 
  might 
  offer 
  differ- 
  

   ences. 
  

  

  Acrolichas 
  robbinsi, 
  PL 
  II, 
  fig. 
  2. 
  This 
  cranidium, 
  

   from 
  the 
  Prosser 
  limestone 
  of 
  Minnesota, 
  bears 
  a 
  striking 
  

   resemblance 
  to 
  Metopolichas 
  long 
  ero 
  stratus 
  (Schmidt) 
  

   (PL 
  IV, 
  fig. 
  2) 
  from 
  the 
  East 
  Baltic 
  provinces 
  of 
  Europe 
  

  

  