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MR.  R.  OWEN  ON  THE  OSTEOLOGY  OF 
contour  of  the  two  skulls  is  greater  than  is  usually  observable  in  those  of  other  wild 
animals  of  the  same  species,  yet  I  do  not  consider  them  sufficient  to  afford  grounds  for 
specific  distinction.  It  is  probable,  however,  that  they  may  be  indicative  of  varieties  of 
the  Orang  inhabiting  distinct  localities  ;  and  it  would  be  interesting  with  that  view  to 
compare  the  crania  of  ascertained  specimens  from  Borneo  and  Sumatra,  to  which  islands 
this  very  remarkable  animal  appears  to  be  confined. 
PLATE  LIV. 
Base  of  the  skull  of  the  adult  Orang  TJtan :  a  tog.  Rudiments  of  the  permanent  teeth 
taken  from  the  jaws  of  an  immature  specimen. 
PLATE  LV. 
Fig.  1 .  Side  view  of  the  skull  of  a  young  Chimpanzee. 
Fig.  2.  Side  view  of  the  skull  of  a  young  Orang  Utan.  These  views  are  both  of 
the  natural  size,  and  taken  at  corresponding  periods  of  dentition,  when  the  permanent 
teeth  are  advanced  to  the  extent  shown  in  the  preceding  figures. 
PLATE  LVL 
Comparative  views  of  the  skulls  of  the  young  and  old  Chimpanzee  and  Orang  Utan, 
showing  the  changes  of  form  they  respectively  undergo  in  attaining  to  maturity. 
Figg.  1,  5.  Young  Chimpanzee. 
2,  6.  Adult  Chimpanzee. 
3,  7.  Young  Orang  Utan. 
4,  8.  Adult  Orang  Utan. 
A  comparison  of  Fig.  1  with  Fig.  2,  and  of  Fig.  3  with  Fig.  4,  will  show  that  those 
differences  between  the  young  and  old  skulls  that  are  present  in  the  Simia  Satyrus,  and 
which  have  been  chiefly  insisted  upon  as  proofs  of  a  specific  difference  between  them, 
obtain  equally  in  the  Simia  Troglodytes. 
Dr.  Harwood  (loc.  cit.,  p.  474,)  observes,  "  But  the  most  distinguishing  difference 
relates  to  the  proportions  of  the  orbits,  and  the  space  which  separates  them.  They  are 
of  by  far  the  greatest  proportionate  size  in  the  Satyrus ;  for  in  the  very  young  animals 
before  alluded  to  they  measure  transversely  1 5  lines  and  a  half,  while  in  the  skull  of  the 
largest  Pongo  ever  brought  to  this  country,  they  extend  no  more  than  17  lines  and  a 
half.  But  the  difference  in  the  extent  of  the  space  between  the  orbits  is  of  all  the  di- 
stinctions I  have  seen  the  most  apparent ;  for  in  the  Satyrus,  where  the  transverse  ex- 
tent of  the  orbits  is  1 5  lines  and  a  half,  and  the  vertical  1 7  and  a  half,  the  space  between 
the  orbits  is  only  2  lines  and  a  half ;  and  in  the  still  younger  Satyrus  at  the  Royal  Insti- 
