MR.  R.  OWEN  ON  THE  ANATOMY  OF  THE  CONCAVE  HORNBILL.  121 
c(Bca,  appear  to  be  adapted  only  for  birds  which,  hke  the  HornUll  and  Toucan,  live 
in  the  midst  of  plenty,  and  can  select  their  food  from  both  kingdoms  of  organized 
nature,  so  abundant  and  so  prolific  in  a  tropical  clime. 
With  respect  to  the  differences  observable  between  these  remarkable  genera,  the 
principal  instances  are  met  with  in  the  locomotive  organs  ;  and  their  affinities  to 
other  tribes,  indicated  by  the  obvious  modifications  of  these  parts,  are  confirmed  by 
the  differences  observable  in  the  internal  organs.  The  Toucan  resembles  the  Psit- 
tacid(E  and  other  Scansores  in  the  absence  of  a  gall-bladder,  while  the  Hornbill,  in  the 
capacity  of  that  receptacle,  manifests  its  affinity  to  the  Corvida.  I  may  also  observe, 
that  the  same  disposition  of  the  intestinal  canal  in  long  and  narrow  loops,  is  met  with 
in  the  Raven  as  in  the  HornUll.  It  is  well  known  that  in  treating  of  the  modifications 
of  the  tongue  in  Birds,  comparative  anatomists  derive  their  most  remarkable  examples 
from  the  Scansorial  order :  its  superior  organization  for  the  sense  of  taste,  from  the 
Psittacida  ;  its  remarkable  structure  as  an  organ  of  prehension,  from  the  Picidce  ;  and 
a  third  modification,  equally  curious,  is  presented  by  the  Toucan,  although  the  pur- 
poses for  which  this  structure  is  adapted  are  less  understood.  The  HornUll,  however, 
in  the  simplicity  of  this  organ,  resembles  the  carnivorous  birds. 
The  individual  from  which  the  preceding  description  was  taken,  was  fed  at  the  Gar- 
dens with  small  birds,  mice,  and  pulpy  fruits  ;  but  it  showed  a  decided  preference  for 
the  animal  diet,  and  would  leave  any  kind  of  food  if  a  dead  mouse  was  thrown  to  it. 
This,  after  two  or  three  squeezes  with  the  beak,  was  gorged  entire.  It  was  never  seen 
to  regurgitate  any  castings  ;  but  I  once  observed  it  bring  up  repeatedly  a  portion  of 
apple,  which  it  endeavoured  to  crush  with  the  points  of  the  mandibles,  and  then  again 
swallowed.  Petiver  gives  direct  testimony  as  to  its  regurgitating  habits,  for  which,  as 
in  the  Toucan,  the  structure  of  the  (esophagus  is  well  adapted.  "  Calao  vel  Cagao  In- 
dorum,  Volucris  &  Montana  est  Avis,  vivens  fructibus  Baliti  s.  ficus  Ind.  Sylv.  Pilis, 
s.  Amygdalo-Pistaceis,  Volvuli  Colyat,  et  aliis,  quos  integros  ingurgitat ;  confecto  vero 
cortice  carnoso,  putamina  ossea  illsesis  nucleis  egerit."^  In  sleeping,  the  bill  is  not  dis- 
posed as  ordinarily  beneath  the  wing,  but  lies  along  the  middle  of  the  back  with  its 
point  directed  forwards,  the  cervical  verteUce  being  acutely  bent  upon  the  dorsal :  the 
Pelican  disposes  in  a  similar  manner  of  its  huge  beak  when  asleep.  The  part  of  the 
wings  corresponding  to  the  carpal  joints  overlap  and  defend  the  bill  from  cold. 
The  HornUll  accommodates  its  habits  and  diet  to  the  country  in  which  it  lives  ; 
being  frugivorous  in  the  Tropics,  and  feeding,  like  the  Vultures  and  Croivs,  on  carrion  in 
the  desert  plains  of  Abyssinia.  We  are  told  by  MM.  Quoy  and  Gaimard,  that  in  the 
Papou  Islands  the  HornUll  sits  on  the  summit  of  the  Nutmeg- tree,  and  with  its 
large  beak  seizes  the  fruit,  and  swallows  it  entire.  The  length  and  wedge-like  form 
of  the  mandibles  are  well  adapted  for  pushing  through  thick  and  interwoven  foliage 
without  endangering  the  eyes  and  other  soft  parts  about  the  head.    I  should  consider 
•  Phil.  Trans.,  vol.  xxiii.  p.  1394. 
