﻿P. 
  E. 
  Raymond 
  — 
  Beecher's 
  Classification 
  of 
  Trilobites. 
  201 
  

  

  impetus 
  of 
  late 
  years 
  by 
  the 
  reference 
  by 
  Lake 
  of 
  Orometopus* 
  

   to 
  the 
  Trinucleidse. 
  (Using 
  Trinueleidse 
  in 
  a 
  broad 
  sense, 
  as 
  

   including 
  the 
  Raphiophoridee.) 
  

  

  The 
  question 
  of 
  the 
  facial 
  suture 
  may 
  be 
  taken 
  up 
  first. 
  

   Reed 
  is 
  the 
  latest 
  writer 
  on 
  the 
  Trinucleidse, 
  and 
  his 
  excellent 
  

   seriesf 
  of 
  papers 
  have 
  added 
  much 
  that 
  was 
  new 
  about 
  the 
  

   family. 
  Dr. 
  Reed 
  seems, 
  however, 
  to 
  have 
  changed 
  his 
  mind 
  

   about 
  the 
  sutures 
  several 
  times 
  in 
  the 
  course 
  of 
  preparation 
  of 
  

   the 
  papers, 
  a 
  thing 
  for 
  which 
  anyone 
  who 
  has 
  studied 
  this 
  puz- 
  

   zling 
  family 
  can 
  readily 
  forgive 
  him. 
  On 
  page 
  170 
  of 
  the 
  con- 
  

   cluding 
  article 
  he 
  states 
  : 
  — 
  "No 
  satisfactory 
  evidence 
  of 
  such 
  

   sutures 
  [across 
  the 
  cheeks 
  and 
  apart 
  from 
  the 
  marginal 
  suture 
  

   round 
  the 
  fringe] 
  in 
  young 
  or 
  adult 
  has 
  been 
  produced, 
  and 
  Mc- 
  

   Coy's 
  figures 
  and 
  description 
  of 
  their 
  presence 
  in 
  his 
  genus 
  

   Tretaspis 
  are 
  not 
  supported 
  by 
  the 
  specimens 
  which 
  he 
  used." 
  

   Yet 
  on 
  the 
  final 
  page 
  he 
  concludes 
  that 
  the 
  fixed 
  and 
  free 
  cheeks 
  

   are 
  fused 
  and 
  the 
  eyes 
  degenerate. 
  He 
  does 
  not 
  anywhere 
  

   deny 
  the 
  reality 
  of 
  the 
  marginal 
  suture, 
  but 
  offers 
  two 
  possible 
  

   explanations 
  of 
  it, 
  the 
  second 
  of 
  which 
  he 
  adopts. 
  Firstly, 
  the 
  

   ventral 
  plate 
  may 
  represent 
  a 
  second 
  undertnrned 
  segment 
  of 
  

   the 
  ancestral 
  annelid, 
  or 
  secondly, 
  the 
  marginal 
  suture 
  may 
  rep- 
  

   resent 
  a 
  secondary 
  facial 
  suture 
  to 
  assist 
  in 
  moulting 
  and 
  com- 
  

   pensate 
  for 
  the 
  one 
  lost 
  by 
  fusion. 
  

  

  The 
  first 
  of 
  these 
  suppositions 
  can 
  not 
  in 
  our 
  present 
  state 
  

   of 
  ignorance 
  of 
  the 
  ancestor 
  of 
  the 
  trilobites 
  be 
  profitably 
  dis- 
  

   cussed. 
  It 
  may 
  be 
  remarked 
  however, 
  that 
  if 
  Bernard 
  was 
  

   right 
  in 
  considering 
  the 
  oculiferous 
  segment 
  of 
  the 
  ancestral 
  

   annelid 
  to 
  have 
  been 
  the 
  first, 
  then 
  another 
  ancestor 
  for 
  Trinu- 
  

   cleus 
  than 
  for 
  the 
  remainder 
  of 
  the 
  trilobites 
  would 
  be 
  called 
  

   for. 
  The 
  second 
  point, 
  however, 
  needs 
  further 
  consideration. 
  

  

  If, 
  as 
  Reed 
  claims, 
  the 
  marginal 
  suture 
  is 
  secondary 
  after 
  

   complete 
  fusion 
  of 
  the 
  primary 
  sutures, 
  then 
  this 
  splitting 
  

   must 
  have 
  taken 
  place 
  after 
  the 
  animal 
  had 
  become 
  fully 
  

   adapted 
  to 
  that 
  mode 
  of 
  life 
  which 
  led 
  to 
  the 
  obliteration 
  of 
  

   the 
  true 
  sutures. 
  In 
  other 
  words, 
  the 
  fringe 
  must 
  have 
  been 
  

   fully 
  developed 
  before 
  the 
  splitting 
  took 
  place. 
  Now 
  what- 
  

   ever 
  the 
  primary 
  functions 
  of 
  the 
  perforations 
  of 
  the 
  fringe, 
  

   the 
  numerous 
  invaginations 
  certainly 
  greatly 
  strengthen 
  the 
  

   brim 
  and 
  reduce 
  rather 
  than 
  enhance 
  the 
  chances 
  that 
  it 
  would 
  

   split. 
  Moreover, 
  if 
  the 
  whole 
  fringe 
  were 
  merely 
  the 
  doublure 
  

   of 
  the 
  free 
  cheeks, 
  as 
  would 
  be 
  necessary 
  in 
  his 
  interpretation, 
  

   why 
  is 
  the 
  pattern 
  of 
  the 
  lower 
  side 
  unlike 
  the 
  upper? 
  The 
  

   fact 
  that 
  the 
  patterns 
  are 
  unlike 
  certainly 
  argues 
  for 
  the 
  inde- 
  

   pendent 
  origin 
  of 
  the 
  lower 
  plate. 
  Among 
  Opisthoparian 
  

  

  * 
  British 
  Cambrian 
  Trilobites, 
  Palaeontogr. 
  Soc, 
  vol. 
  lxi, 
  p. 
  46, 
  pi. 
  4, 
  figs. 
  

   6-10, 
  1907. 
  

  

  t 
  Geol. 
  Mag. 
  Dec. 
  5, 
  vol. 
  ix, 
  pp. 
  346 
  and 
  385, 
  1912 
  ; 
  Dec. 
  6, 
  vol. 
  i. 
  p. 
  349, 
  

   1914 
  ; 
  Dec. 
  6, 
  vol. 
  iii, 
  pp. 
  118 
  and 
  169, 
  1916. 
  

  

  