﻿188 
  Mr. 
  M. 
  A. 
  ('. 
  Hinton 
  

  

  (b) 
  Forest-Bed 
  Beavers. 
  

  

  Forsyth 
  Major 
  * 
  lias 
  shown 
  that 
  two 
  species 
  of 
  Castor 
  

   occur 
  in 
  the 
  Forest-Bed 
  lioiizon 
  exposed 
  at 
  East 
  Runton, 
  

   Norfolk. 
  One, 
  characterized 
  bj 
  its 
  broader 
  incisors, 
  slightly 
  

   larger 
  cheek-teeth, 
  and, 
  above 
  all, 
  by 
  the 
  " 
  complex 
  and 
  

   elegant 
  plication 
  " 
  of 
  the 
  enamel 
  of 
  its 
  molars, 
  is 
  identical 
  

   with 
  C. 
  plicide7is, 
  Major, 
  a 
  species 
  described 
  from 
  the 
  Upper 
  

   Pliocene 
  of 
  the 
  Val 
  d'Arno 
  ; 
  the 
  other, 
  with 
  narrower 
  iricisors, 
  

   smaller 
  molars, 
  and 
  much 
  less 
  plicated 
  enamel, 
  makes 
  a 
  

   nearer 
  approach 
  to 
  the 
  recent 
  species, 
  and 
  it 
  is 
  the 
  only 
  form 
  

   whicli 
  has 
  been 
  found 
  hitherto 
  in 
  the 
  Upper 
  Freshwater 
  Bed 
  

   at 
  WestRunton. 
  Recently 
  Mr. 
  Savin 
  has 
  found 
  in 
  the 
  latter 
  

   deposit 
  two 
  young 
  U})per 
  cheek-teeth 
  of 
  Castor, 
  each 
  being 
  

   eitlier 
  the 
  right 
  ^ 
  or 
  ^J 
  (pi_ 
  ym. 
  f^gg. 
  2 
  & 
  3). 
  Each 
  tooth 
  

   presents 
  the 
  usual 
  enamel 
  pattern, 
  and 
  in 
  each 
  the 
  enamel, 
  as 
  

   exposed 
  at 
  the 
  grinding-surface 
  (figs. 
  2 
  a, 
  3 
  a), 
  is 
  free 
  from 
  

   jilication. 
  An 
  examination 
  of 
  their 
  bases 
  shows 
  that, 
  while 
  

   in 
  the 
  smaller 
  tooth 
  the 
  enamel 
  would 
  remain 
  unerimped 
  

   (fig. 
  3 
  b), 
  in 
  the 
  larger 
  one 
  (fig. 
  2 
  h) 
  it 
  acquires 
  in 
  deeper 
  strata 
  

   of 
  the 
  crown 
  the 
  complex 
  and 
  elegant 
  plication 
  of 
  C. 
  plicidens. 
  

   Boscot 
  has 
  shown 
  that 
  the 
  jaw 
  from 
  the 
  Val 
  d'Arno, 
  on 
  

   which 
  Forsyth 
  ilajor 
  based 
  his 
  C. 
  rosinai\^ 
  is, 
  in 
  fact, 
  a 
  

   young 
  jaw 
  of 
  C. 
  plicidens 
  ; 
  the 
  enamel 
  at 
  the 
  grinding- 
  

   surface 
  of 
  the 
  little-worn 
  teeth 
  of 
  this 
  jaw 
  is 
  free 
  from 
  plica- 
  

   tion, 
  but 
  a 
  section 
  made 
  through 
  the 
  basal 
  parts 
  of 
  the 
  teeth 
  

   shows 
  that 
  the 
  ty})ical 
  ])lication 
  is 
  developed 
  in 
  the 
  deeper 
  

   portions 
  of 
  the 
  teeth, 
  just 
  as 
  in 
  the 
  West 
  Runton 
  specimen. 
  

   it 
  may 
  be 
  mentioned, 
  further, 
  that 
  whereas 
  in 
  the 
  molars 
  of 
  

   the 
  loAver 
  jaw 
  from 
  East 
  Runton 
  figured 
  by 
  Forsyth 
  Major 
  

   the 
  jilication 
  principally 
  affects 
  the 
  enamel 
  of 
  the 
  first 
  and 
  

   third 
  inner 
  folds, 
  in 
  the 
  West 
  Runton 
  tooth 
  all 
  three 
  of 
  the 
  

   corresponding 
  oute)- 
  folds 
  display 
  it. 
  

  

  Mr. 
  Savin 
  possesses 
  a 
  large 
  right 
  ramus 
  from 
  the 
  Forest 
  

   Bed 
  of 
  Bacton 
  with 
  all 
  the 
  teeth 
  in 
  place. 
  It 
  belonged 
  to 
  an 
  

   old 
  individual. 
  The 
  molars 
  are 
  greatly 
  worn 
  and 
  some 
  of 
  

   them 
  are 
  mutilated 
  ; 
  tlieir 
  crowns 
  still 
  show, 
  particularly 
  in 
  

   the 
  antero-internal 
  fold 
  of 
  each 
  tooth, 
  traces 
  of 
  a 
  strong- 
  

   plication 
  of 
  the 
  enamel. 
  The 
  incisor 
  is 
  very 
  broad. 
  This 
  

   jaw 
  also 
  may, 
  peihaps, 
  be 
  referable 
  to 
  C. 
  plicidens. 
  

  

  * 
  Forsytli 
  Major, 
  Proc. 
  Zool. 
  Soc. 
  1908, 
  p. 
  630. 
  

  

  t 
  Bosco, 
  o}). 
  cit. 
  p. 
  88. 
  

  

  ;J; 
  Forsyth 
  Major, 
  Arch, 
  per 
  I'autrop. 
  e 
  Tetnografia, 
  vol, 
  vi. 
  p. 
  'Mo 
  (1870). 
  

  

  