MR.  E.  T.  BENNETT  ON  THE  CHINCHILLID^. 
55 
cylindrical  ;  and  they  are  all,  except  the  smaller  terminal  ones,  furnished  with  V-shaped 
apophyses.  The  sternum  is  composed  of  six  bony  pieces,  in  addition  to  the  xiphoid  car- 
tilage ;  of  these  the  manubrium  is  long,  hroadly  expanded  in  its  anterior  half,  and  some- 
what paddle-shaped  ;  the  penultimate  is  by  much  the  smallest.  Seven  pairs  of  the  ribs 
are  directly  articulated  with  the  sternum. 
The  clavicle  is  perfect,  but  slender  and  slightly  curved ;  and  the  scapula  small,  with 
the  spine  nearly  median  and  httle  elevated  posteriorly,  but  terminating  in  a  long  acro- 
mion, the  free  portion  of  the  spine  being  nearly  equal  to  the  whole  attached  length.  On  the 
outer  and  upper  part  of  the  humerus  there  is  a  strongly  marked  deltoid  process,  from  which 
a  ridge  is  continued  downwards.  The  olecranon  is  large ;  and  the  radius  and  ulna,  although 
distinct,  are  so  closely  applied  to  each  other  at  their  carpal  extremity,  as  to  appear  an- 
chylosed  for  one  half  of  their  length  in  Chinchilla,  and  one  fourth  in  Lagotis.  The  four 
fingers  of  Lagotis  are  composed  of  three  phalanges,  additional  to  the  metacarpal  bones, 
and  there  is  not  the  smallest  vestige  of  a  thumb.  In  Chinchilla  the  phalanges  of  the  cor- 
responding fingers  are  formed  upon  the  same  plan  ;  and  the  thumb  has  two  distinct  pha- 
langes in  addition  to  its  proper  metacarpal  bone.  The  pelvis  is  long  and  narrow,  the  crista 
of  the  ilia  being  much  extended  forwards,  and  the  great  size  of  the  obturator  foramina 
giving  rise  to  a  similar  projection  of  the  ischia  backwards.  The  femur  is  straight  and 
cylindrical ;  it  is  half  as  long  again  as  the  humerus.  The  tibia  is  twice  the  length  of 
the  radius.  The  fibula  is  complete  and  detached,  but  very  slender.  The  length  of  the 
soles  of  the  hinder  feet,  from  the  calcaneum  to  the  tip  of  the  longest  toe,  is  nearly  three 
times  that  of  the  anterior  from  the  carpal  articulation  outwards.  The  whole  length  of 
the  free  portion  of  the  posterior  limbs  is  consequently  about  double  that  of  the  anterior. 
The  metatarsal  bones  are  four  in,  number ;  and  each  toe  has  three  phalanges,  the  outer- 
most of  the  four  just  reaching  the  base  of  the  next  adjoining  toe. 
The  comparative  measurements  of  the  bones  in  the  two  animals  are  as  follow  : — 
Lagotis. 
No. 
Ft. 
In. 
No. 
Ft.  In. 
Length  of  the  head  .... 
3-2 
2-3 
 vertebra,  cervical 
7  . 
1-3 
7  . 
•8 
 dorsal 
12  . 
3-3 
13  . 
2-3 
 lumbar 
7  . 
3-6 
6  . 
2-2 
 sacral 
2  . 
•8 
2  . 
•5 
 caudal 
27  . 
.  1 
0-4 
23  , 
6- 
Total  length  .    .  . 
.  2 
0-6 
1  2-1 
Length  of  the  skull  .... 
3-2 
2-3 
Breadth  of  do. 
at  the  meatus  auditorii  . 
zygomata  . 
1-5 
1-7 
Chinchilla. 
1-2 
1-2 
