﻿American 
  Ordovician 
  LichadidcE. 
  47 
  

  

  toward 
  such 
  pygidia 
  in 
  Platopolichas 
  avus, 
  Platopolichas 
  

   incola, 
  and 
  in 
  various 
  species 
  of 
  Dicranopeltis 
  is 
  suffi- 
  

   ciently 
  strong 
  to 
  indicate 
  the 
  possibility 
  of 
  such 
  pygidia 
  

   as 
  those 
  associated 
  by 
  Schmidt 
  with 
  Metalichas 
  in 
  genera 
  

   not 
  closely 
  related 
  to 
  either 
  Acrolichas 
  nor 
  Amphilichas. 
  

  

  At 
  present, 
  the 
  identity 
  of 
  Amphilichas 
  rests 
  upon 
  the 
  

   glabella 
  figured 
  by 
  Schmidt, 
  in 
  his 
  figure 
  5 
  on 
  Plate 
  6, 
  

   under 
  the 
  name 
  Lichas 
  laevis 
  Eichwald. 
  This 
  is 
  a 
  most 
  

   peculiar 
  glabella, 
  with 
  elongate 
  elliptical 
  rather 
  than 
  

   reniform 
  side 
  lobes, 
  resulting 
  in 
  a 
  rotund 
  outline 
  of 
  the 
  

   glabella 
  as 
  a 
  whole. 
  The 
  anterior 
  glabellar 
  furrows 
  tend 
  

   to 
  terminate 
  posteriorly 
  before 
  reaching 
  the 
  occipital 
  

   furrow, 
  especially 
  in 
  case 
  of 
  the 
  outer 
  surface 
  of 
  the 
  test. 
  

  

  In 
  such 
  species 
  as 
  Lichas 
  holmi 
  Schmidt 
  and 
  Lichas 
  

   dalecarlica 
  Angelin, 
  the 
  reniform 
  side 
  lobes 
  of 
  the 
  gla- 
  

   bella 
  suggest 
  closer 
  relationship 
  with 
  Acrolichas, 
  but, 
  in 
  

   the 
  absence 
  of 
  pygidia 
  of 
  the 
  Acrolichas 
  type, 
  strict 
  

   identity 
  remains 
  uncertain. 
  

  

  Under 
  these 
  circumstances 
  it 
  seems 
  preferable 
  to 
  em- 
  

   phasize 
  the 
  wide 
  range 
  of 
  species 
  of 
  the 
  Acrolichas 
  type 
  

   in 
  America, 
  and 
  the 
  lack 
  of 
  definite 
  knowledge 
  of 
  cor- 
  

   responding 
  pygidia 
  in 
  the 
  Baltic 
  areas 
  of 
  Europe, 
  than 
  

   to 
  assume 
  that 
  similarity 
  of 
  glabellar 
  alone 
  is 
  sufficient 
  to 
  

   establish 
  the 
  identity 
  of 
  Acrolichas 
  with 
  Amphilichas, 
  

   thus, 
  by 
  inference, 
  assuming 
  that 
  the 
  European 
  species 
  

   of 
  Amphilichas 
  also 
  have 
  the 
  Acrolichas 
  type 
  of 
  pygi- 
  

   dium. 
  To 
  the 
  present 
  writer 
  it 
  seems 
  preferable 
  to 
  await 
  

   the 
  results 
  of 
  further 
  research. 
  

  

  17. 
  Bibliography. 
  

  

  A 
  full 
  bibliography 
  of 
  American 
  Ordovician 
  and 
  Silu- 
  

   rian 
  Lichads 
  is 
  presented 
  by 
  Bassler, 
  in 
  his 
  Biblio- 
  

   graphic 
  Index 
  of 
  American 
  Ordovician 
  and 
  Silurian 
  

   Fossils, 
  published 
  in 
  1915. 
  Under 
  the 
  genus 
  Lichas, 
  

   references 
  to 
  all 
  the 
  more 
  important 
  foreign 
  publications 
  

   on 
  the 
  Lichadidse 
  are 
  presented. 
  Among 
  these 
  the 
  fol- 
  

   lowing 
  are 
  of 
  especial 
  interest, 
  in 
  connection 
  with 
  the 
  

   recognition 
  of 
  generic 
  types: 
  Dames, 
  Zeitschrift 
  d. 
  

   deutsch. 
  geol. 
  Gesell., 
  29, 
  1877, 
  pp. 
  793-815. 
  Giirich, 
  

   Neues 
  Jahrbuch 
  Min. 
  Geol. 
  Pal., 
  17, 
  Beilage 
  Band, 
  1901. 
  

   Schmidt, 
  Mem. 
  PAcad. 
  Imp. 
  Sci. 
  St. 
  Petersbourg, 
  33, 
  

   1885. 
  ^ 
  Eeed, 
  Quart. 
  Jour. 
  Geol. 
  Soc. 
  London, 
  58, 
  1902. 
  

   To 
  this 
  should 
  be 
  added, 
  especially 
  for 
  Silurian 
  genera, 
  

   Hawle 
  and 
  Corda, 
  Abh. 
  d. 
  k. 
  Bohmischen 
  Gesell. 
  d. 
  Wiss., 
  

  

  