﻿20± 
  P. 
  E. 
  Raymond 
  — 
  Beecher's 
  Classification 
  of 
  Trilobites. 
  

  

  than 
  such 
  a 
  form 
  as 
  Orometopus. 
  In 
  fact, 
  the 
  row 
  of 
  pustules 
  

   on 
  the 
  border 
  of 
  some 
  species 
  of 
  Eodisous 
  foreshadows 
  to 
  

   some 
  extent 
  the 
  Trinucleid 
  fringe. 
  The 
  ontogeny 
  of 
  such 
  a 
  

   species 
  as 
  Cryptolithus 
  ornatus 
  (Sternberg) 
  shows 
  that 
  in 
  the 
  

   youngest 
  stages 
  now 
  known 
  the 
  cephalon 
  of 
  Cryptolithus 
  has 
  

   a 
  narrow 
  brim 
  without 
  pits, 
  that 
  at 
  the 
  same 
  time 
  as 
  the 
  devel- 
  

   opment 
  of 
  the 
  first 
  thoracic 
  segment 
  a 
  single 
  row 
  of 
  pits 
  is 
  

   present, 
  and 
  with 
  increasing 
  growth 
  the 
  brim 
  widens 
  with 
  

   successive 
  rows 
  of 
  pits. 
  It 
  is 
  interesting 
  to 
  note 
  that 
  the 
  

   cephalon 
  of 
  the 
  oldest 
  of 
  the 
  Trinucleids, 
  Trinucleus 
  reussi 
  

   Barrande, 
  shows 
  in 
  the 
  adult 
  a 
  form 
  corresponding 
  to 
  the 
  

   second 
  stage 
  in 
  the 
  development 
  of 
  Cryptolithus 
  ornatus^ 
  hav- 
  

   ing 
  but 
  a 
  single 
  well 
  developed 
  row 
  of 
  pits 
  on 
  its 
  narrow 
  

   brim, 
  and 
  showing 
  the 
  same 
  large 
  side 
  lobes 
  on 
  the 
  glabella. 
  

   This 
  form 
  I 
  propose 
  to 
  make 
  the 
  type 
  of 
  a 
  separate 
  genus, 
  

   Trinucleoides. 
  

  

  To 
  summarize 
  for 
  the 
  Trinucleidae 
  then, 
  it 
  may 
  be 
  said 
  : 
  — 
  

   firstly, 
  that 
  there 
  is 
  no 
  positive 
  evidence 
  that 
  the 
  free 
  and 
  fixed 
  

   cheeks 
  are 
  fused, 
  Reed 
  having 
  definitely 
  shown 
  that 
  the 
  suture 
  

   of 
  McCoy 
  is 
  not 
  a 
  facial 
  suture. 
  

  

  Secondly, 
  the 
  ventral 
  plate 
  is 
  an 
  easily 
  separable 
  and 
  inde- 
  

   pendent 
  plate, 
  bounded 
  by 
  sutures 
  which 
  on 
  Beecher's 
  con- 
  

   ception 
  of 
  the 
  morphology 
  of 
  the 
  head 
  would 
  be 
  the 
  facial 
  

   sutures. 
  

  

  Thirdly, 
  Orometopus 
  does 
  not 
  in 
  itself 
  present 
  any 
  very 
  

   strong 
  evidence 
  that 
  it 
  is 
  the 
  ancestor 
  of 
  the 
  Trinucleidse. 
  

  

  Fourthly, 
  the 
  ontogeny 
  of 
  the 
  Trinucleids 
  points 
  to 
  an 
  iso- 
  

   pygous 
  ancestor 
  with 
  ventral 
  free 
  cheeks, 
  of 
  the 
  same 
  type 
  as 
  

   Eodiscidse 
  or 
  Aomostidse. 
  

  

  Until 
  some 
  stronger 
  evidence 
  of 
  the 
  degeneracy 
  of 
  the 
  

   Trinucleids 
  from 
  an 
  Opisthoparian 
  ancestor 
  is 
  adduced, 
  I 
  think 
  

   the 
  family 
  may 
  safely 
  be 
  left 
  in 
  the 
  Hypoparia. 
  

  

  Raphiophorido2. 
  — 
  Professor 
  Swinnerton 
  is 
  entirely 
  correct 
  

   when 
  he 
  states 
  that 
  the 
  Raphiophoridse 
  " 
  are 
  presumably 
  

   placed 
  in 
  the 
  Hypoparia 
  because 
  of 
  their 
  evident 
  relationship 
  

   to 
  the 
  Trinucleidse." 
  It 
  is 
  no 
  part 
  of 
  the 
  function 
  of 
  a 
  " 
  natural 
  " 
  

   classification 
  to 
  force 
  apart 
  evidently 
  related 
  families 
  merely 
  to 
  

   be 
  consistent 
  with 
  the 
  definitions. 
  The 
  more 
  natural 
  a 
  classi- 
  

   fication 
  is, 
  the 
  more 
  impossible 
  it 
  is 
  to 
  frame 
  definitions 
  which 
  

   are 
  rigid. 
  The 
  word 
  " 
  generally 
  " 
  must 
  be 
  freely 
  used 
  or 
  

   understood. 
  That 
  the 
  highest 
  families 
  of 
  one 
  order 
  should 
  

   parallel 
  the 
  lowest 
  of 
  a 
  more 
  advanced 
  order 
  is 
  to 
  be 
  expected, 
  

   and 
  may 
  be 
  construed 
  as 
  furnishing 
  a 
  proof 
  of 
  the 
  success 
  

   of 
  a 
  classification, 
  rather 
  than 
  as 
  militating 
  against 
  it. 
  

  

  The 
  Raphiophoridae 
  furnish 
  one 
  point 
  of 
  considerable 
  interest 
  

   in 
  connection 
  with 
  this 
  discussion. 
  It 
  is 
  generally 
  accepted 
  

   that 
  the 
  epistoma 
  and 
  the 
  free 
  cheeks 
  are 
  parts 
  of 
  the 
  same 
  

  

  