THE  CHIMPANZEE  AND  ORANG  UTAN. 
377 
d,  e.  The  two  bicuspides. 
f.  The  first  true  molar,  its  fangs  yet  imperfect. 
g.  The  second  molar. 
On  the  right  hand,  a  front  view  is  given  of  the  first  and  second  permanent  incisors,  as 
they  appear  partly  worn  down  in  the  adult. 
PLATE  LII. 
The  base  of  the  skull  of  the  adult  Chimpanzee,  natural  size.  The  rudiments  of  the  per- 
manent teeth,  a  to  g,  are  figured  in  a  position  corresponding  to  those  in  the  jaws  of  the 
adult.  The  formation  of  the  last  molar,  or  dens  sapientits,  h,  had  not  commenced  in 
the  young  cranium  from  which  the  rest  of  the  permanent  teeth  were  taken. 
PLATE  LIIL 
Side  view  of  the  cranium  oi  an  adult  Orang  Utan.  A  front  view  of  the  first  perma- 
nent incisor,  d,  and  the  rudiments  of  the  permanent  teeth,  a  to  g,  from  the  jaws  of  a 
young  Orang  are  subjoined,  proving  its  identity  with  the  adult,  or  supposed  Pongo. 
This  Plate  is  taken  from  a  cranium  in  the  possession  of  Mr.  Cross,  of  the  Surrey 
Zoological  Gardens,  who  obligingly  sent  his  specimen  to  me  for  the  purpose  of  describing 
and  figuring  it.  On  comparing  it  with  the  skull  of  the  Pongo,  or  adult  Orang,  in  the 
Museum  of  the  College  of  Surgeons,  I  noted  the  following  differences  : 
The  skull  belonging  to  Mr.  Cross  is  shorter  in  the  antero-posterior  diameter,  and  rises 
higher  at  the  vertex.  The  supra-orbitary  ridges  are  more  prominent ;  the  plane  of  the 
orbits  is  more  vertical,  and  their  lateral  exceeds  their  perpendicular  diameter.  The 
profile  line  of  the  skull  is  concave  between  the  glabella  and  incisor  teeth,  while  in  the 
specimen  in  the  Museum  of  the  College  it  is  almost  a  straight  line  between  the  same 
parts.  The  symphysis  of  the  jaw,  from  the  interspace  of  the  mesial  incisors  to  the  origin 
of  the  genio-hyoidei  muscles,  measures  2i-  inches  in  Mr.  Cross's  specimen,  but  equals 
34-  inches  in  the  Pongo  in  the  College  Museum.  There  is  also  a  remarkable  difference 
in  the  position  of  the  zygomatic  suture :  in  the  Pongo  of  the  College  Museum  it  com- 
mences at  the  distance  of  a  quarter  of  an  inch  from  the  orbital  process  of  the  malar  bone 
and  extends  obliquely  backwards  to  within  1^  inch  of  the  origin  of  the  zygomatic  pro- 
cess of  the  temporal  bone  ;  in  Mr.  Cross's  specimen,  the  same  suture  commences 
8  lines  from  the  orbital  process  of  the  malar  bone  and  extends  to  within  10  lines  of  the 
origin  of  the  temporal  zygomatic  suture,  so  that  it  is  much  nearer  the  middle  of  the 
zygoma. 
With  these  differences,  however,  there  exist  the  same  form  and  proportions  of  the 
teeth,  and  the  same  peculiarities  of  the  foramina  and  sutures  which  distinguish  the 
Orang  from  the  Chimpanzee.    So  that,  although  the  difference  in  the  shape  and  general 
