﻿some 
  Remains 
  of 
  Rodents. 
  191 
  

  

  narrower, 
  so 
  tliat 
  its 
  plan 
  is 
  triangular 
  instead 
  of 
  nearly 
  

   rectangular. 
  In 
  the 
  beaver 
  the 
  astragalean 
  facette 
  is 
  a 
  

   circular, 
  rather 
  deep 
  basin, 
  with 
  a 
  well-defined 
  posterior 
  rim, 
  

   occupying 
  about 
  half 
  of 
  the 
  proximal 
  surface 
  ; 
  in 
  the 
  fossil 
  it 
  

   is 
  a 
  rather 
  shallow, 
  irregularly 
  shaped 
  concavity, 
  with 
  an 
  

   ill-defined 
  posterior 
  margin 
  occupying 
  fully 
  two-thirds 
  of 
  the 
  

   proximal 
  surface. 
  The 
  distal 
  surface 
  presents 
  the 
  usual 
  

   three 
  facettes 
  for 
  the 
  cuneiforms, 
  and 
  these 
  have 
  a 
  greater 
  

   antero-posterior 
  extent 
  than 
  in 
  the 
  beaver. 
  The 
  facette 
  for 
  

   cuneiform 
  III. 
  is 
  nearly 
  plane 
  instead 
  of 
  concave 
  antero- 
  

   posteriorly 
  ; 
  that 
  for 
  cuneiform 
  11. 
  is 
  relatively 
  wider 
  and 
  

   gently 
  convex 
  from 
  behind 
  forwards, 
  instead 
  of 
  nearly 
  fiat. 
  

   Tlie 
  facette 
  for 
  cuneiform 
  I. 
  is 
  large, 
  crescentic, 
  and 
  concave, 
  

   forming 
  the 
  anterior 
  side 
  and 
  roof 
  of 
  a 
  profound 
  notch 
  which 
  

   cuts 
  almost 
  through 
  the 
  bone 
  from 
  the 
  distal 
  to 
  the 
  proximal 
  

   surface; 
  in 
  the 
  beaver 
  this 
  notch 
  is 
  much 
  less 
  deep 
  and 
  

   the 
  facette 
  is 
  greatly 
  reduced 
  and 
  convex, 
  only 
  tiie 
  anterior 
  

   part 
  of 
  the 
  facette 
  of 
  the 
  fossil 
  being 
  represented. 
  On 
  tlie 
  

   other 
  hand, 
  in 
  the 
  beaver 
  the 
  anterior 
  face 
  of 
  tl\e 
  greatly 
  

   developed 
  descending 
  process 
  or 
  " 
  spur 
  " 
  boars 
  a 
  small 
  addi- 
  

   tional 
  facette 
  for 
  the 
  posterior 
  margin 
  of 
  cuneiform 
  I., 
  which 
  

   is 
  not 
  represented 
  in 
  the 
  fossil. 
  Between 
  the 
  superior 
  border 
  

   of 
  the 
  chief 
  facette 
  for 
  cuneiform 
  I. 
  and 
  the 
  astra^-alean 
  

   surface 
  there 
  is 
  in 
  the 
  beaver 
  a 
  rather 
  large, 
  slightly 
  inclined, 
  

   oval 
  facette 
  for 
  the 
  '^ 
  naviculare 
  tibiale^' 
  ; 
  in 
  the 
  fossil 
  this 
  

   facette 
  is 
  also 
  present, 
  but 
  is 
  narrower, 
  triangnlar 
  in 
  shape, 
  

   and 
  highly 
  inclined. 
  The 
  outer 
  (fibular) 
  side 
  of 
  the 
  bone 
  is 
  

   occupied 
  anteriorly 
  by 
  the 
  cuboid 
  facette. 
  In 
  the 
  beaver 
  

   this 
  is 
  relatively 
  short, 
  low 
  behind, 
  its 
  j)lane 
  nearly 
  vertical, 
  

   and 
  very 
  slightly 
  concave 
  antero-posteriorly. 
  In 
  the 
  fossil 
  

   it 
  is 
  longer, 
  much 
  higher 
  behind, 
  its 
  nearly 
  vertical 
  anterior 
  

   portion 
  faces 
  backwards 
  and 
  outwards, 
  and 
  its 
  oblique 
  hinder 
  

   part 
  faces 
  slightly 
  forwards, 
  downwards, 
  and 
  outwards; 
  the 
  

   outer 
  border 
  of 
  the 
  bone, 
  when 
  viewed 
  from 
  below, 
  conse- 
  

   quently 
  appears 
  widely 
  notched 
  instead 
  of 
  straight 
  or 
  gently 
  

   concave. 
  The 
  posterior 
  spur 
  is 
  much 
  le.ss 
  developed 
  than 
  in 
  

   the 
  beaver 
  ; 
  in 
  the 
  latter 
  its 
  plan 
  is 
  nearly 
  square, 
  its 
  flat 
  

   upper 
  surface 
  ascends 
  posteriorly, 
  while 
  below 
  it 
  is 
  produced 
  

   as 
  a 
  massive 
  projection 
  descending 
  considerably 
  below 
  the 
  

   general 
  level 
  of 
  the 
  distal 
  surface 
  ; 
  in 
  the 
  fossil 
  it 
  is 
  narrower, 
  

   its 
  upper 
  surface 
  is 
  rounded 
  and 
  shelves 
  away 
  behind 
  and 
  

   laterally, 
  while 
  below 
  the 
  descending 
  process 
  is 
  little 
  developed 
  

   and 
  scarcely 
  attains 
  the 
  level 
  ot 
  tlie 
  distal 
  surface. 
  The 
  

   measurements 
  recorded 
  in 
  the 
  following 
  table 
  bring 
  out 
  many 
  

   important 
  distinctions 
  : 
  — 
  

  

  