﻿some 
  Remains 
  of 
  Rodents. 
  

  

  195 
  

  

  verse 
  crest 
  startincr 
  from 
  its 
  posterior 
  part 
  instead 
  of 
  from 
  

   cusp 
  5. 
  As 
  a 
  result 
  of 
  these 
  differences 
  the 
  anterior 
  and 
  

   posterior 
  transverse 
  valleys 
  are 
  less 
  extensive, 
  the 
  central 
  

   one, 
  ou 
  the 
  other 
  hand, 
  wider 
  and 
  deeper 
  than 
  in 
  S. 
  vulgaris. 
  

   Viewed 
  from 
  the 
  front, 
  the 
  fossil 
  is 
  seen 
  to 
  be 
  rather 
  more 
  

   brachyodont 
  than 
  the 
  recent 
  tooth. 
  Like 
  the 
  latter, 
  the 
  

   fossil 
  has 
  three 
  roots, 
  viz., 
  a 
  large 
  fang 
  supporting 
  the 
  inner 
  

   cone 
  and 
  two 
  small 
  ones 
  on 
  the 
  outer 
  side 
  ; 
  in 
  the 
  fossil 
  the 
  

   outer 
  fangs 
  are 
  of 
  approximately 
  equal 
  size, 
  but 
  in 
  b. 
  vulgaris, 
  

   owing 
  to 
  the 
  greater 
  size 
  of 
  cusp 
  1, 
  the 
  antero-external 
  fang 
  

   is 
  stouter 
  than 
  the 
  postero-external 
  one. 
  As 
  the 
  following- 
  

   dimensions 
  show, 
  the 
  fossil 
  is 
  considerably 
  smaller 
  than 
  the 
  

   recent 
  tooth 
  : 
  — 
  

  

  EXPLANATION 
  OF 
  PLATE 
  VIII. 
  

  

  Fig, 
  1. 
  Castor 
  veterior, 
  Lankester. 
  Part 
  of 
  a 
  right 
  ramus, 
  witn 
  ^, 
  ^TT, 
  

   and 
  11^2, 
  from 
  the 
  Red 
  Crag 
  of 
  Woodbridge, 
  Suffolk. 
  Major 
  

   Moore's 
  collection. 
  A, 
  inner, 
  B, 
  outer 
  view 
  ; 
  C, 
  crown 
  view 
  

   of 
  cheek-teeth. 
  

  

  Fig. 
  2. 
  Castor 
  plicidens, 
  Forsyth 
  Major, 
  from 
  the 
  Upper 
  Freshwater 
  Bed 
  

   of 
  West 
  Runton, 
  Norfolk, 
  a, 
  crown, 
  b, 
  basal 
  view. 
  

  

  Fig. 
  3. 
  Castor 
  sp., 
  from 
  the 
  Upper 
  Freshwater 
  Bed 
  of 
  West 
  Runton. 
  

   rt, 
  crown, 
  6, 
  basal 
  view. 
  

  

  Figs. 
  4 
  & 
  5. 
  Trogontherium. 
  Lateral 
  and 
  sectional 
  views 
  of 
  two 
  young 
  

   left 
  upper 
  incisors 
  from 
  the 
  Upper 
  Freshwater 
  Bed 
  of 
  West 
  

   Runton. 
  

  

  Fig. 
  6. 
  Trogontherium. 
  Left 
  lower 
  incisor 
  from 
  the 
  Upper 
  Freshwater 
  

   Bed 
  of 
  West 
  Runton. 
  6 
  a. 
  Posterior 
  view 
  of 
  tip. 
  6 
  h. 
  Ante- 
  

   rior 
  view 
  of 
  tip. 
  (6 
  a 
  and 
  6 
  much 
  enlarged.) 
  

  

  Fig. 
  7. 
  Trogontherium 
  cuviei-i, 
  Fischer. 
  Right 
  navicular 
  from 
  the 
  Upper 
  

   Freshwater 
  Bed, 
  West 
  Runton. 
  A 
  = 
  proximal, 
  B= 
  distal, 
  

   C 
  = 
  tibial, 
  and 
  D 
  = 
  tibular 
  views. 
  Facettes 
  : 
  «, 
  astragalean 
  ; 
  

   c, 
  cuboid 
  ; 
  HI., 
  II., 
  and 
  I., 
  cuneiform, 
  n.t., 
  naviculare 
  tibiale. 
  

  

  Fig. 
  8. 
  Castor 
  fiber, 
  Linn. 
  Right 
  navicular 
  from 
  the 
  alluvium 
  of 
  the 
  

   Thames. 
  Lettering 
  as 
  in 
  tig. 
  7. 
  

  

  Fig. 
  9. 
  Sciurvs 
  vulgaris, 
  Linn. 
  Right 
  P"^ 
  ^ 
  , 
  recent. 
  X 
  9. 
  

  

  lig. 
  10. 
  Sciurus 
  wititei, 
  s^.n. 
  Right 
  P™- 
  ^ 
  from 
  the 
  Upper 
  Freshwater 
  ' 
  

   Bed, 
  West 
  Runton. 
  X 
  9. 
  

  

  (Except 
  where 
  otherwise 
  noted, 
  all 
  figures 
  are 
  of 
  natural 
  size.) 
  

  

  