﻿THE 
  EXTINCT 
  VERTEBRATE 
  ANIMALS 
  

  

  Scotland 
  been 
  as 
  yet 
  only 
  found 
  at 
  Scaat 
  Craig. 
  I 
  have 
  hazarded 
  

   the 
  opinion 
  that 
  they 
  belong 
  to 
  Holoptychius 
  nobilissimus 
  (48, 
  p. 
  35). 
  

   Teeth 
  of 
  a 
  similar 
  shape 
  occur 
  in 
  the 
  allied 
  H. 
  Flemingii, 
  Agassiz, 
  

   from 
  Dura 
  Den, 
  in 
  Fifeshire. 
  

  

  In 
  this 
  category 
  I 
  must 
  place 
  the 
  tooth 
  figured 
  by 
  Duff 
  (7, 
  

   Plate 
  vi. 
  fig. 
  11) 
  as 
  Dendrodus 
  incurvus, 
  and 
  refigured 
  by 
  Agassiz 
  

   as 
  the 
  type 
  of 
  his 
  genus 
  Cricodus. 
  I 
  may 
  here 
  quote 
  my 
  own 
  

   words, 
  as 
  published 
  in 
  1892 
  (48, 
  p. 
  35): 
  — 
  'Agassiz's 
  genus 
  

   Cricodus 
  has 
  been 
  referred 
  to 
  the 
  Rhizodontidse 
  by 
  myself 
  and 
  

   Mr. 
  Smith 
  Woodward 
  on 
  account 
  of 
  Pander's 
  identification 
  

   of 
  it 
  with 
  his 
  Polyplocodus, 
  which 
  assuredly 
  belongs 
  to 
  that 
  

   family, 
  and 
  also 
  because 
  the 
  transverse 
  section 
  of 
  a 
  tooth 
  figured 
  

   by 
  Agassiz 
  as 
  Cricodus, 
  without 
  specific 
  name 
  (Poiss. 
  Foss., 
  vol. 
  ii. 
  

   pt. 
  i. 
  tab. 
  H, 
  figs. 
  11, 
  12), 
  is 
  apparently 
  of 
  Rhizodont 
  character. 
  

   But 
  Agassiz 
  in 
  the 
  text 
  (ibid. 
  p. 
  156) 
  states 
  that 
  the 
  tooth 
  from 
  

   which 
  this 
  section 
  was 
  taken 
  had 
  its 
  large 
  pulp-cavity 
  filled 
  with 
  a 
  

   black 
  matrix 
  ; 
  likewise 
  that 
  it 
  was 
  a 
  fragment 
  broken 
  at 
  both 
  ends 
  

   which 
  1 
  provenait 
  d'une 
  dent 
  enorme, 
  car 
  il 
  avait 
  la 
  grosseur 
  d'un 
  

   doigt.' 
  It 
  is 
  therefore 
  almost 
  certain 
  that 
  this 
  Rhizodont 
  tooth, 
  

   which 
  he 
  says 
  is 
  from 
  Scotland, 
  without 
  naming 
  any 
  precise 
  

   locality, 
  is 
  of 
  carboniferous 
  age, 
  especially 
  seeing 
  that 
  a 
  few 
  pages 
  

   further 
  back 
  (ibid. 
  p. 
  105) 
  he 
  states 
  that 
  Cricodus 
  occurs 
  both 
  in 
  

   Devonian 
  and 
  Carboniferous 
  rocks. 
  It 
  is 
  certainly 
  very 
  different 
  

   from 
  the 
  tooth 
  figured 
  by 
  Duff 
  as 
  Dendrodus 
  incurvus, 
  which 
  Agassiz 
  

   afterwards 
  refigured 
  in 
  his 
  Fossil 
  Fishes 
  of 
  the 
  Old 
  Bed 
  Sandstone 
  as 
  

   Cricodus 
  incurvus, 
  and 
  apparently 
  adopted 
  as 
  the 
  type 
  of 
  the 
  genus, 
  

   seeing 
  that 
  he 
  named 
  no 
  other 
  species; 
  for 
  on 
  examining 
  this 
  

   species 
  of 
  incurvus 
  I 
  found, 
  somewhat 
  to 
  my 
  surprise, 
  that 
  it 
  was 
  

   in 
  reality 
  a 
  Dendrodont 
  or 
  Holoptychian 
  tooth, 
  apparently 
  be- 
  

   longing 
  to 
  Owen's 
  species 
  D. 
  sigmoideus, 
  and 
  this, 
  I 
  have 
  long 
  been 
  

   convinced, 
  is 
  synonymous 
  with 
  Holoptychius 
  nobilissimus 
  of 
  Agassiz. 
  

   The 
  name 
  Cricodus 
  must 
  therefore 
  drop, 
  as 
  no 
  genus 
  can 
  be 
  

   founded 
  on 
  the 
  fragment 
  of 
  which 
  a 
  section 
  is 
  figured 
  in 
  Agassiz's 
  

   larger 
  work.' 
  

  

  Family 
  RHIZODONTID^I. 
  

  

  Genus 
  POLYPLOCODUS, 
  Pander. 
  

   Fragments 
  of 
  dentigerous 
  bones, 
  not 
  at 
  present 
  determinable, 
  but 
  

   showing 
  roots 
  of 
  Rhizodont 
  teeth, 
  from 
  Scaat 
  Craig, 
  in 
  the 
  

   Edinburgh 
  Museum. 
  

  

  