﻿182 
  Beecliev 
  — 
  Natural 
  Classification 
  of 
  the 
  Trilobites. 
  

  

  limitations 
  of 
  the 
  families. 
  This 
  would 
  require 
  discussions 
  of 
  

   priority 
  and 
  synonymy, 
  and 
  otherwise 
  detract 
  from 
  the 
  direct 
  

   purpose 
  of 
  the 
  writer 
  ; 
  viz., 
  to 
  establish 
  a 
  basis 
  for 
  a 
  natural 
  

   classification, 
  and 
  in 
  this 
  way 
  to 
  apply 
  what 
  is 
  currently 
  known 
  

   and 
  accepted 
  regarding 
  the 
  trilobites. 
  Nevertheless, 
  some 
  

   notice 
  must 
  be 
  taken 
  of 
  several 
  families 
  and 
  genera 
  which 
  for 
  

   various 
  reasons 
  do 
  not 
  appear 
  here. 
  The 
  family 
  Aglaspidae, 
  

   including 
  the 
  genus 
  Aglaspis 
  Hall, 
  proves 
  to 
  belong 
  to 
  the 
  

   Merostomata, 
  and 
  is 
  therefore 
  omitted. 
  The 
  family 
  Bohemil- 
  

   lidse 
  has 
  been 
  shown 
  by 
  the 
  writer 
  6 
  to 
  have 
  no 
  foundation, 
  

   because 
  the 
  type 
  of 
  the 
  genus 
  Bohemilla 
  Barrande 
  was 
  based 
  

   upon 
  a 
  mutilated 
  specimen 
  of 
  ^Eglina. 
  

  

  

  

  •c 
  

  

  ft 
  

   O 
  

   Oh 
  

  

  >> 
  

  

  w 
  

  

  o 
  

  

  1 
  

  

  O 
  

  

  .2 
  

  

  a 
  

  

  PL, 
  

  

  o 
  

  

  < 
  

  

  H 
  

  

  W 
  

   O 
  

  

  Permian. 
  

  

  

  1 
  

  

  

  1 
  

  

  Carboniferous. 
  

  

  

  

  

  1 
  

  

  Devonian. 
  

  

  

  1 
  

  

  t 
  

  

  i 
  

  

  Silurian. 
  

  

  

  A 
  

  

  Ordovician. 
  

  

  I 
  

  

  ii 
  

  

  Cambrian. 
  

  

  1 
  

  

  i 
  j 
  

  

  

  i 
  j 
  

  

  Pre-Cambrian. 
  

  

  

  v 
  

  

  

  

  Table 
  of 
  Geological 
  Distribution 
  of 
  Trilobites. 
  

  

  Several 
  genera 
  still 
  commonly 
  adopted 
  are 
  not 
  here 
  recog- 
  

   nized 
  in 
  the 
  lists 
  under 
  the 
  families, 
  since 
  from 
  the 
  minute 
  

   size 
  of 
  the 
  individuals 
  described 
  and 
  their 
  immature 
  charac- 
  

   ters, 
  they 
  must 
  be 
  considered 
  as 
  the 
  young 
  of 
  larger 
  forms. 
  

   Such 
  are 
  Conqphrys 
  Callaway, 
  Cyphoniscus 
  Salter, 
  Holometo- 
  

   jpus 
  Angelin, 
  Isooolus 
  Angelin, 
  and 
  Shumardia 
  Billings. 
  Trio- 
  

   pus 
  Barrande 
  has 
  been 
  shown 
  to 
  be 
  a 
  chiton. 
  

  

  Much 
  could 
  be 
  said 
  against 
  some 
  of 
  the 
  recognized 
  genera, 
  

   but, 
  as 
  with 
  the 
  families, 
  the 
  writer 
  has 
  preferred 
  in 
  almost 
  

   every 
  case 
  to 
  adopt, 
  for 
  the 
  present, 
  what 
  has 
  been 
  commonly 
  

   accepted, 
  and 
  thus 
  to 
  avoid 
  the 
  entanglements 
  of 
  dates 
  and 
  

   synonyms 
  which 
  would 
  be 
  out 
  of 
  place 
  in 
  any 
  general 
  discus- 
  

   sions. 
  The 
  type 
  species 
  of 
  every 
  genus 
  is 
  here 
  made 
  the 
  cen- 
  

   tral 
  idea. 
  It 
  is 
  taken 
  as 
  representing 
  the 
  genus 
  more 
  closely 
  

   than 
  any 
  fortuitous 
  assemblage 
  of 
  diverse 
  species, 
  which 
  the 
  

  

  