﻿some 
  Remains 
  of 
  Rodents. 
  193 
  

  

  tlie 
  tliird 
  and 
  fourth 
  toes 
  in 
  the 
  foot 
  of 
  the 
  beaver 
  is 
  a 
  feature 
  

   seen 
  also 
  in 
  the 
  feet 
  of 
  many 
  otlier 
  aquatic 
  mammals, 
  and 
  is 
  

   a 
  specialization 
  for 
  swinnning. 
  From 
  the 
  circumstance 
  that, 
  

   judging 
  from 
  the 
  navicular, 
  these 
  two 
  digits 
  were 
  less 
  

   specially 
  favoured 
  in 
  Troyoiitherium, 
  we 
  may 
  infer 
  that 
  the 
  

   latter 
  was 
  less 
  aquatic 
  than 
  Castor. 
  

  

  Since 
  writing 
  the 
  above 
  paragraph 
  1 
  have 
  read 
  Owen's 
  

   account* 
  of 
  some 
  limb-bones 
  referred 
  by 
  him 
  to 
  Trogontherium. 
  

   They 
  included 
  the 
  humerus, 
  femur, 
  tibia 
  and 
  anchylosed 
  

   fibula, 
  and 
  the 
  calcaneura. 
  The 
  humerus 
  was 
  much 
  larger 
  

   proportionally, 
  the 
  femur 
  much 
  shorter 
  in 
  relation 
  to 
  the 
  tibia, 
  

   than 
  in 
  Castor. 
  The 
  femur 
  is 
  clearly 
  much 
  less 
  specialized, 
  

   differing 
  principally 
  in 
  the 
  smaller 
  and 
  more 
  highly 
  placed 
  

   third 
  trochanter, 
  the 
  rounder 
  and 
  thicker 
  lateral 
  borders 
  of 
  

   its 
  distal 
  half, 
  and 
  its 
  slighter 
  distal 
  expansion. 
  The 
  tibia 
  is 
  

   longer 
  and 
  has 
  a 
  shallower 
  posterior 
  groove, 
  and 
  the 
  fibula 
  is 
  

   more 
  extensively 
  anchylosed 
  with 
  it 
  below. 
  The 
  calcaneum 
  

   presents 
  features 
  analogous 
  to 
  those 
  described 
  in 
  the 
  navicular. 
  

   As 
  in 
  the 
  latter 
  the 
  posterior 
  non-articular 
  part 
  is 
  shorter 
  

   relatively, 
  the 
  articular 
  part 
  more 
  largely 
  developed; 
  it 
  is 
  

   also 
  broader, 
  and 
  there 
  are 
  similar 
  diflerences 
  in 
  the 
  form 
  and 
  

   curvature 
  of 
  the 
  facettes. 
  It 
  is 
  with 
  satisfaction 
  that 
  I 
  note 
  

   that 
  Owen 
  inferred 
  " 
  from 
  the 
  femoral 
  modifications 
  that 
  the 
  

   Trogontlierhun 
  was 
  less 
  aquatic 
  and 
  a 
  swifter 
  mover 
  upon 
  

   laud 
  than 
  the 
  beaver." 
  

  

  Sciurus 
  whiteij 
  sp. 
  n. 
  

  

  Many 
  years 
  ago 
  Oswald 
  Heer 
  f 
  noticed 
  that 
  some 
  of 
  the 
  

   fir-cones 
  from 
  the 
  Forest 
  Bed 
  bore 
  marks 
  which 
  appeared 
  to 
  

   indicate 
  that 
  they 
  had 
  been 
  gnawed 
  by 
  squirrels. 
  The 
  only 
  

   additional, 
  and 
  quite 
  doubtful, 
  evidence 
  of 
  such 
  an 
  animal 
  in 
  

   the 
  Cromerian 
  fauna 
  which 
  Mr. 
  Newton 
  was 
  able 
  to 
  record 
  in 
  

   1882 
  was 
  that 
  of 
  a 
  humerus 
  in 
  the 
  Green 
  Collection 
  from 
  

   Ostend, 
  Norfolk; 
  this 
  bone 
  agrees 
  closely 
  in 
  form 
  with 
  that 
  

   of 
  IS. 
  vulgaris, 
  and 
  it 
  is 
  not 
  certain 
  whetlier 
  it 
  came 
  from 
  the 
  

   Forest 
  Bed 
  or 
  from 
  a 
  recent 
  alluvial 
  deposit. 
  Until 
  the 
  

   discovery 
  to 
  be 
  described 
  here 
  was 
  made, 
  no 
  further 
  trace 
  of 
  a 
  

   squirrel 
  has 
  been 
  met 
  with 
  in 
  the 
  Forest 
  Bed. 
  A 
  few 
  years 
  

   ago, 
  when 
  he 
  was 
  collecting 
  from 
  the 
  thin 
  bed 
  known 
  as 
  the 
  

  

  * 
  Owen, 
  Geol. 
  Mag. 
  dec. 
  1, 
  vol. 
  vi. 
  p. 
  52 
  (1869). 
  

  

  t 
  Newton, 
  " 
  Vertebrata 
  of 
  the 
  Forest 
  Bed,'' 
  Mem. 
  Geol. 
  Survey, 
  1882, 
  

   p. 
  92. 
  

  

  Ann. 
  d& 
  Mag. 
  JS. 
  Hist. 
  Ser. 
  8. 
  Vol. 
  xiii. 
  13 
  

  

  