﻿XX11 
  INTRODUCTION. 
  

  

  degenerate 
  survivors. 
  It 
  is 
  equally 
  impossible 
  to 
  justify 
  the 
  

   conception 
  of 
  the 
  groups 
  " 
  Lepidosteoidei 
  " 
  and 
  " 
  Amioidei," 
  most 
  

   of 
  the 
  extinct 
  fishes 
  which 
  are 
  still 
  commonly 
  ascribed 
  to 
  the 
  

   former 
  being 
  proved 
  in 
  the 
  Catalogue 
  to 
  be 
  much 
  more 
  closely 
  

   related 
  to 
  the 
  latter. 
  

  

  This 
  result 
  is 
  merely 
  the 
  logical 
  outcome 
  of 
  the 
  new 
  departure 
  

   in 
  Ichthyology 
  made 
  by 
  Traquair 
  in 
  1876, 
  1 
  when 
  he 
  published 
  his 
  

   classic 
  memoir 
  on 
  the 
  systematic 
  position 
  of 
  the 
  Palseoniscidse. 
  

   The 
  characters 
  which 
  Traquair's 
  researches 
  have 
  proved 
  to 
  be 
  

   secondary 
  in 
  the 
  group 
  to 
  which 
  these 
  typically 
  Palaeozoic 
  fishes 
  

   belong, 
  are 
  similarly 
  shown 
  to 
  be 
  of 
  comparatively 
  small 
  taxonomic 
  

   value 
  in 
  the 
  higher 
  groups 
  of 
  Mesozoic 
  age 
  to 
  which 
  the 
  present 
  

   volume 
  specially 
  refers. 
  It 
  therefore 
  seems 
  unnecessary 
  to 
  recapi- 
  

   tulate 
  and 
  discuss 
  the 
  various 
  classifications 
  which 
  have 
  been 
  

   proposed 
  ; 
  for 
  nearly 
  all 
  of 
  them, 
  even 
  those 
  published 
  during 
  the 
  

   last 
  fifteen 
  years, 
  fail 
  to 
  distinguish 
  between 
  the 
  fundamental 
  and 
  

   the 
  secondary 
  features, 
  which 
  the 
  memoirs 
  cited 
  have 
  made 
  quite 
  

   clear. 
  

  

  It 
  only 
  remains 
  to 
  add 
  that, 
  in 
  a 
  work 
  of 
  this 
  kind, 
  a 
  more 
  or 
  

   less 
  definite 
  judgment 
  must 
  sometimes 
  be 
  pronounced 
  in 
  cases 
  

   where 
  the 
  known 
  facts 
  , 
  scarcely 
  suffice 
  for 
  more 
  than 
  premature 
  

   speculation 
  ; 
  and 
  it 
  is 
  always 
  difficult 
  to 
  express 
  a 
  tentative 
  result 
  

   in 
  terms 
  which 
  cannot 
  be 
  exaggerated 
  in 
  quotation. 
  The 
  present 
  

   volume, 
  like 
  its 
  predecessors, 
  is 
  therefore 
  to 
  be 
  accepted 
  merely 
  as 
  

   a 
  convenient 
  basis 
  for 
  further 
  research, 
  full 
  of 
  imperfections 
  which 
  

   each 
  specialist 
  will 
  readily 
  discover 
  for 
  himself. 
  A 
  few 
  partly 
  

   novel 
  conceptions 
  have 
  been 
  introduced, 
  to 
  direct 
  attention 
  to 
  

   certain 
  problems 
  which 
  seem 
  hitherto 
  to 
  have 
  been 
  inadequately 
  

   considered. 
  A 
  careful 
  examination 
  of 
  nearly 
  all 
  the 
  available 
  

   specimens 
  has 
  enabled 
  the 
  writer 
  to 
  attempt 
  a 
  more 
  detailed 
  

   account 
  of 
  the 
  osteology 
  of 
  the 
  principal 
  genera 
  than 
  has 
  previously 
  

   been 
  published. 
  For 
  continued 
  generous 
  co-operation, 
  thanks 
  are 
  

   not 
  only 
  due 
  to 
  the 
  many 
  scientific 
  colleagues 
  at 
  home 
  and 
  abroad, 
  

   to 
  whom 
  indebtedness 
  has 
  already 
  been 
  expressed 
  in 
  the 
  previous 
  

   volumes 
  ; 
  they 
  are 
  likewise 
  gratefully 
  tendered 
  to 
  the 
  Government 
  

  

  1 
  E. 
  H. 
  Traquair, 
  ' 
  The 
  Ganoid 
  Fishes 
  of 
  the 
  British 
  Carboniferous 
  Forma- 
  

   tions,' 
  Part 
  I. 
  (Mon. 
  Palseont. 
  Soc., 
  1876). 
  See 
  also 
  Memoir 
  on 
  Platysomidse 
  

   already 
  quoted, 
  and 
  " 
  Eeport 
  on 
  Fossil 
  Fishes 
  collected 
  by 
  the 
  Geological 
  

   Survey 
  of 
  Scotland 
  in 
  Eskdale 
  and. 
  Liddesdale," 
  Trans. 
  Eoy. 
  Soc. 
  Edinb. 
  

   vol. 
  xxx. 
  pp. 
  15-71, 
  pis. 
  i.-vi. 
  (1881), 
  and 
  " 
  Notes 
  on 
  Chondrosteus 
  acipen- 
  

   Agassiz," 
  Geol. 
  Mag. 
  [3] 
  vol. 
  iv. 
  pp. 
  248-257, 
  figs. 
  1-5 
  (1887). 
  

  

  