﻿Mr. 
  R. 
  Lydekker 
  on 
  Nototlierium 
  and 
  Zygornaturus. 
  151 
  

  

  Mr. 
  De 
  Vis 
  (I. 
  c. 
  p. 
  115) 
  that 
  the 
  Nototherium 
  skull 
  was 
  of 
  

   the 
  Diprotodont 
  type 
  and 
  unlike 
  no. 
  33259. 
  

  

  Again, 
  Mr. 
  De 
  Vis 
  states 
  (p. 
  116) 
  that 
  the 
  mandible 
  of 
  

   the 
  so-called 
  Zygomaturus 
  is 
  unknown 
  ; 
  but 
  no. 
  33259 
  has 
  

   with 
  it 
  the 
  cast 
  of 
  a 
  mandible 
  which 
  appears 
  to 
  have 
  been 
  taken 
  

   from 
  a 
  specimen 
  associated 
  with 
  the 
  cranium. 
  This 
  man- 
  

   dible, 
  although 
  not 
  showing 
  the 
  premolar, 
  is 
  that 
  of 
  a 
  typical 
  

   Nototherium. 
  

  

  Sufficient 
  has 
  now 
  been 
  said 
  to 
  show 
  that 
  Mr. 
  De 
  Vis 
  has 
  

   not 
  a 
  leg 
  to 
  stand 
  upon 
  in 
  the 
  new 
  view 
  propounded 
  ; 
  and 
  

   since 
  he 
  suggests 
  that 
  the 
  humerus 
  in 
  question 
  may 
  have 
  

   belonged 
  to 
  his 
  so-called 
  Zygomaturus, 
  the 
  original 
  reference 
  

   of 
  that 
  bone 
  to 
  Nototherium 
  remains, 
  at 
  least 
  for 
  the 
  present, 
  

   undisturbed. 
  

  

  There 
  is, 
  however, 
  still 
  the 
  question 
  as 
  to 
  what 
  the 
  tooth 
  

   on 
  the 
  right 
  side 
  of 
  no. 
  33259 
  really 
  is. 
  Now 
  it 
  appears 
  to 
  

   me 
  that 
  this 
  tooth 
  is 
  either 
  an 
  abnormality, 
  or 
  that 
  it 
  is 
  not 
  

   homologous 
  with 
  the 
  tooth 
  on 
  the 
  left 
  side, 
  or 
  that 
  it 
  has 
  been 
  

   inserted 
  in 
  a 
  skull 
  to 
  which 
  it 
  does 
  not 
  belong 
  *. 
  The 
  last 
  

   suggestion 
  appears 
  to 
  me 
  to 
  be 
  the 
  most 
  probable 
  one, 
  although 
  

   it 
  would 
  leave 
  unexplained 
  to 
  what 
  animal 
  this 
  tooth 
  and 
  the 
  

   somewhat 
  similar 
  one 
  figured 
  by 
  Mr. 
  De 
  Vis 
  really 
  belong. 
  

   It 
  is 
  clear 
  that 
  the 
  skull 
  in 
  question 
  is 
  adult, 
  so 
  that 
  this 
  

   tooth 
  cannot 
  be 
  pm 
  - 
  3 
  if 
  it 
  belong 
  to 
  that 
  skull, 
  while 
  its 
  dis- 
  

   similarity 
  from 
  the 
  true 
  molars 
  forbids 
  the 
  view 
  that 
  it 
  can 
  be 
  

  

  mm. 
  4 
  

  

  On 
  the 
  other 
  hand, 
  there 
  is 
  a 
  certain 
  similarity 
  between 
  

   this 
  tooth 
  and 
  some 
  specimens 
  of 
  ' 
  )m 
  - 
  4 
  of 
  Diprotodon, 
  although 
  

   it 
  is 
  larger 
  than 
  any 
  specimens 
  of 
  that 
  tooth 
  which 
  I 
  have 
  

   seen. 
  Assuming 
  that 
  this 
  type 
  of 
  tooth 
  is 
  not 
  an 
  abnormal 
  

   last 
  premolar 
  of 
  Nototherium, 
  it 
  may 
  be 
  suggested 
  that 
  

   it 
  may 
  possibly 
  be 
  the 
  deciduous 
  ?™^? 
  of 
  Diprotodon. 
  

   So 
  far 
  as 
  we 
  know 
  at 
  present 
  there 
  is 
  no 
  evidence 
  of 
  any 
  

   tooth- 
  change 
  or 
  of 
  the 
  presence 
  of 
  a 
  deciduous 
  pm 
  - 
  3 
  in 
  either 
  

   Diprotodon 
  or 
  Nototherium 
  ; 
  but 
  the 
  loss 
  of 
  such 
  change 
  

   being 
  evidently 
  an 
  acquired 
  character, 
  we 
  might 
  reasonably 
  

   expect 
  to 
  meet 
  with 
  reversionary 
  instances 
  in 
  which 
  such 
  

   a 
  change 
  took 
  place. 
  The 
  rarity 
  of 
  this 
  type 
  of 
  tooth, 
  to 
  

   which 
  Mr. 
  De 
  Vis 
  alludes, 
  so 
  far 
  as 
  it 
  goes, 
  is 
  in 
  favour 
  of 
  

   this 
  suggestion. 
  

  

  I 
  can 
  of 
  course 
  say 
  nothing 
  as 
  to 
  what 
  may 
  be 
  the 
  nature 
  

   of 
  the 
  crushed 
  Diprotodon-like 
  skulls 
  which 
  Mr. 
  De 
  Vis 
  would 
  

  

  * 
  In 
  ■writing 
  the 
  ' 
  Catalogue' 
  my 
  attention 
  was 
  not 
  especially 
  directed 
  

   to 
  this 
  discrepancy 
  in 
  the 
  two 
  teeth. 
  I 
  may 
  take 
  this 
  opportunity 
  of 
  

   stating 
  that 
  no. 
  47840 
  (Cat. 
  p. 
  108), 
  which 
  was 
  labelled 
  by 
  Sir 
  E,. 
  Owen 
  

   Nototherium 
  Mitchelli, 
  and 
  so 
  catalogued, 
  really 
  belongs 
  to 
  Diprotodon. 
  

  

  