THE INTERNAL SKELETON, 187 
bone, the palatine is also pushed forward. These simultaneous 
forward thrusts, bend the apex of the upper jaw slightly upwards, 
flexing the skull where the nasals and lateral ethmoids join the 
frontals. But this movement of the upper jaw is very much 
more extensive in the Parrots, where a regular joint extends 
across the skull just in front of the frontals, and facilitates that 
extreme mobility of the upper part of the bill, which is so 
evident when a Parrot eats. 
The Os hyoides or Hyoid.—This curiously shaped bone con- 
sists normally of a central portion formed of two ossicles—one 
in front of the other—and of two pairs of slender and more or 
less elongated branches—called “horns” or cornua, ‘The front 
part of the hyoid lies between and below the rami of the lower 
Fig. 153. 


Os HYOIDES OF A CRANE. 
b, Basi-byal ; g, glosso-hyal ; ge, gc, greater cornua or thyro-hyals ; 
le, 7c, lesser cornua or cerato-hya!s; wu, urohyal. 
? ’ d 7 ’ a 
jaw, with its cornua extending backwards and more or less up- 
wards behind the head. It is entirely disconnected with the rest 
of the cranial skeleton save by soft structures, except that some- 
times (as in Woodpeckers) the apices of the cornua are applied 
to one side of the skull beneath the orbit or within the nasal 
opening. 
The posterior of the two median bones is called the basi- 
hyal and is generally short and thick, but is sometimes slender ; 
the anterior one is the glosso-hyal, and lies within the tongue. A 
bony process which often projects, tipped with cartilage, back- 
wards from the basihyal is called the wro-hyal, and may be a 
distinct bone. 
To either side of the front part of the basi-hyal a styliform 
bone is generally articulated, and may be short or more or less 
elongated. This and its fellow of the opposite side constitute the 
“lesser horns,” lesser cornua, or cornicula, or cerato-hyals. A 
