﻿30 
  A. 
  F. 
  Foerste 
  — 
  Relations 
  of 
  the 
  

  

  second 
  annulation 
  usually 
  terminates 
  before 
  reaching 
  

   tlie^ 
  dorsal 
  furrows. 
  There 
  are 
  three 
  pairs 
  of 
  lateral 
  ribs, 
  

   all 
  with 
  free 
  tips. 
  Each 
  of 
  the 
  anterior 
  pair 
  of 
  ribs 
  is 
  

   traversed 
  by 
  a 
  diagonal 
  furrow 
  starting 
  near 
  the 
  an- 
  

   terior 
  margin 
  of 
  the 
  rib. 
  The 
  diagonal 
  furrow 
  on 
  each 
  

   of 
  the 
  second 
  pair 
  of 
  ribs 
  starts 
  farther 
  back 
  from 
  the 
  

   anterior 
  margin 
  of 
  this 
  rib. 
  The 
  third 
  or 
  posterior 
  pair 
  

   of 
  ribs 
  is 
  without 
  any 
  distinct 
  trace 
  of 
  a 
  diagonal 
  furrow, 
  

   the 
  latter 
  evidently 
  having 
  become 
  obsolete 
  in 
  this 
  generic 
  

   group 
  of 
  species. 
  (Ohio 
  Journal 
  of 
  Science, 
  19, 
  p. 
  402, 
  

   1919; 
  Bull. 
  Denison 
  Univ., 
  19, 
  p. 
  72, 
  1919, 
  pi. 
  17, 
  figs. 
  

  

  4A 
  > 
  R 
  ) 
  

  

  The 
  following 
  seven 
  species 
  (one 
  of 
  which 
  is 
  from 
  

  

  Ireland), 
  known 
  both 
  from 
  their 
  cranidia 
  and 
  from 
  their 
  

   pygidia, 
  evidently 
  belong 
  to 
  Acrolichas. 
  (For 
  biblio- 
  

   graphic 
  references 
  see 
  Bassler's 
  Bibliographic 
  Index 
  of 
  

   American 
  Ordovician 
  and 
  Silurian 
  Fossils, 
  1915.) 
  

  

  Lichas 
  minganensis 
  Billings, 
  PL 
  III, 
  figs. 
  I 
  A, 
  B, 
  C, 
  from 
  

   the 
  Chazyan 
  of 
  eastern 
  Canada, 
  Vermont, 
  New 
  York, 
  and 
  

   Virginia. 
  

  

  Lichas 
  cucullus 
  Meek 
  and 
  "Worthen, 
  PI. 
  I, 
  figs. 
  1 
  A-G, 
  

   from 
  the 
  Kimmswick, 
  Prosser, 
  and 
  Trenton 
  of 
  Missouri, 
  

   Illinois, 
  Wiconsin, 
  Minnesota, 
  and 
  in 
  the 
  Lake 
  Winnipeg 
  

   and 
  Ottawa 
  areas 
  of 
  Canada. 
  Also 
  from 
  the 
  Richmond 
  of 
  

   northern 
  Michigan. 
  

  

  Lichas 
  trentonensis 
  (Conrad), 
  PI. 
  I, 
  figs. 
  3 
  A, 
  B 
  ; 
  PI. 
  Ill, 
  

   figs. 
  4 
  A-D, 
  from 
  the 
  Trenton 
  of 
  Pennsylvania, 
  New 
  Jersey, 
  

   and 
  New 
  York. 
  (Not 
  identified 
  with 
  certainty 
  from 
  Canada 
  

   or 
  Missouri.) 
  

  

  Lichas 
  (Conolichas) 
  comutus 
  Clarke, 
  PI. 
  I, 
  fig. 
  5; 
  PI. 
  Ill, 
  

   figs. 
  5 
  A-C, 
  from 
  the 
  Trenton 
  of 
  New 
  York. 
  

  

  Amphilichas 
  conifrons 
  Ruedemann, 
  PI. 
  I, 
  figs. 
  4 
  A-C 
  

   (Bull. 
  New 
  York 
  State 
  Mns., 
  No. 
  189, 
  p. 
  90, 
  PL 
  30, 
  figs. 
  5-8), 
  

   from 
  the 
  Trenton 
  of 
  New 
  York. 
  

  

  Lichas 
  harrisi 
  Miller, 
  PL 
  III, 
  figs. 
  6 
  A-C, 
  from 
  the 
  Liberty 
  

   member 
  of 
  the 
  Richmond, 
  in 
  Ohio. 
  

  

  Lichas 
  hibemicus 
  (Portlock), 
  PL 
  III, 
  figs. 
  9 
  A, 
  B 
  (Geol. 
  

   of 
  Londonderry, 
  Tyrone, 
  and 
  Fermanagh, 
  1843, 
  p. 
  274, 
  Pis. 
  

   IV 
  and 
  V), 
  from 
  the 
  Llandeilo 
  of 
  Ireland. 
  

  

  To 
  this 
  list 
  probably 
  should 
  be 
  added 
  the 
  following 
  

   five 
  species, 
  known 
  only 
  from 
  their 
  cranidia 
  : 
  

  

  Lichas 
  jukesii 
  Billings, 
  PL 
  II, 
  figs. 
  1 
  A, 
  B, 
  from 
  the 
  

   Chazyan 
  of 
  eastern 
  Canada. 
  

  

  Lichas 
  {Hoplolichas) 
  robbinsi 
  Ulrich, 
  PL 
  II, 
  fig. 
  2, 
  from 
  

   the 
  Prosser 
  of 
  Minnesota. 
  

  

  