﻿200 
  P. 
  E. 
  Raymond 
  — 
  Beecher 
  s 
  Classification 
  of 
  Trilobites. 
  

  

  dse 
  was 
  in 
  the 
  Lower 
  Cambrian, 
  and 
  the 
  specimens 
  bearing 
  the 
  

   eyes 
  are 
  from 
  the 
  Middle 
  Cambrian. 
  Not 
  only 
  that, 
  but 
  these 
  

   species 
  are 
  highly 
  specialized 
  eodiscids, 
  as 
  is 
  shown 
  by 
  the 
  

   reduction 
  to 
  two 
  thoracic 
  segments, 
  the 
  practical 
  obliteration 
  

   of 
  furrows 
  on 
  the 
  pleural 
  lobes 
  of 
  the 
  pygidium, 
  and 
  the 
  great 
  

   axial 
  spines, 
  especially 
  in 
  Pagetia 
  bootes. 
  

  

  The 
  discovery 
  of 
  a 
  genus 
  with 
  two 
  species 
  which 
  bear 
  eyes 
  

   very 
  close 
  to 
  the 
  lateral 
  margins 
  seems 
  to 
  be 
  a 
  confirmation 
  of 
  

   the 
  previous 
  supposition 
  that 
  the 
  Eodiscidse 
  have 
  ventral 
  

   free 
  cheeks. 
  Since 
  the 
  great 
  majority, 
  including 
  the 
  most 
  primi- 
  

   tive 
  of 
  the 
  genera 
  and 
  species 
  of 
  this 
  family, 
  do 
  not 
  show 
  

   free 
  cheeks 
  on 
  the 
  dorsal 
  surface 
  and 
  so 
  come 
  within 
  the 
  limits 
  

   of 
  the 
  Hypoparia 
  as 
  defined 
  by 
  Beecher, 
  it 
  seems 
  to 
  me 
  that 
  the 
  

   family 
  should 
  remain 
  in 
  that 
  order. 
  Like 
  the 
  Agnostidse, 
  the 
  

   Eodiscidse 
  appear 
  to 
  have 
  Proparian 
  tendencies. 
  

  

  Shumardidce. 
  — 
  These 
  little 
  trilobites 
  are 
  still 
  too 
  much 
  of 
  a 
  

   puzzle 
  to 
  be 
  discussed 
  at 
  any 
  length, 
  and 
  the 
  ultimate 
  disposition 
  

   of 
  the 
  family 
  has 
  no 
  particular 
  bearing 
  upon 
  the 
  question 
  at 
  

   hand. 
  

  

  ParjJedidce. 
  — 
  Of 
  this 
  family 
  I 
  have 
  no 
  personal 
  knowledge, 
  

   but 
  as 
  its 
  principal 
  characteristics 
  are 
  even 
  more 
  primitive 
  than 
  

   those 
  of 
  the 
  Trinucleidse 
  and 
  as 
  the 
  organization 
  of 
  its 
  cephalon 
  

   is 
  so 
  closely 
  parallel 
  to 
  that 
  of 
  the 
  latter 
  group, 
  I 
  do 
  not 
  yet 
  see 
  

   any 
  particular 
  reason 
  to 
  remove 
  the 
  family 
  from 
  the 
  position 
  

   in 
  which 
  Beecher 
  placed 
  it. 
  

  

  I 
  have 
  the 
  paper 
  by 
  Kichter 
  mentioned 
  by 
  Swinnerton, 
  

   and 
  though 
  I 
  have 
  the 
  greatest 
  respect 
  for 
  the 
  work 
  of 
  Dr. 
  

   and 
  Fran 
  Richter, 
  still 
  Middle 
  Devonian 
  species 
  of 
  Harpes 
  can 
  

   not 
  be 
  considered 
  as 
  exactly 
  the 
  ones 
  to 
  study 
  in 
  getting 
  at 
  the 
  

   primitive 
  characteristics 
  of 
  this 
  group. 
  There 
  seems 
  no 
  apriovi 
  

   reason 
  why 
  simple 
  or 
  aggregate 
  eyes 
  should 
  not 
  develop 
  on 
  

   trilobites 
  absolutely 
  independently 
  of 
  the 
  compound 
  eye, 
  and 
  

   the 
  presence 
  of 
  such 
  eyes 
  in 
  a 
  Silurian 
  or 
  Devonian 
  trilobite 
  

   whose 
  ancestors 
  were 
  more 
  nearly 
  blind 
  does 
  not 
  seem 
  any 
  

   proof 
  at 
  all 
  that 
  they 
  are 
  remnants 
  of 
  fully 
  developed 
  com- 
  

   pound 
  eyes. 
  

  

  Trinucleidm. 
  — 
  It 
  is 
  in 
  connection 
  with 
  this 
  family 
  that 
  the 
  

   principal 
  objection 
  against 
  the 
  order 
  Hypoparia 
  has 
  been 
  raised. 
  

   The 
  present 
  opinion 
  of 
  a 
  number 
  of 
  paleontologists, 
  best 
  sum- 
  

   marized 
  by 
  Swinnerton, 
  is 
  that 
  the 
  Trinucleidae 
  are 
  degenerate 
  

   descendents 
  of 
  trilobites 
  with 
  eyes, 
  that 
  the 
  free 
  and 
  fixed 
  cheeks 
  

   are 
  coalesced 
  with 
  the 
  obliteration 
  of 
  the 
  suture, 
  and 
  that 
  the 
  

   ocelli 
  on 
  the 
  cheeks 
  represent 
  the 
  degenerate 
  remains 
  of 
  com- 
  

   pound 
  eyes. 
  These 
  paleontologists 
  believe 
  that 
  the 
  facial 
  suture 
  

   of 
  McCoy 
  is 
  the 
  real 
  facial 
  suture 
  and 
  either 
  deny 
  the 
  presence 
  

   or 
  question 
  the 
  morphology 
  of 
  the 
  facial 
  suture 
  of 
  Barrande. 
  

   This 
  idea 
  is 
  of 
  course 
  not 
  new, 
  but 
  has 
  been 
  given 
  especial 
  

  

  