THE CRANIAL PECULIARITIES OF THE WOODPECKERS. 117 
18. NOTE ON SOME OF THE CRANIAL PECU- 
LIARITIES OF THE WOODPECKERS.* 
Constperinc the method adopted by the Woodpeckers for obtaining page 357. 
their food, it is hardly surprising that they possess cranial features 
- peculiar to themselves; for it is scarcely conceivable that the head, 
the most delicately constructed portion of the body, should be em- 
ployed as a powerful hammer or axe whose stroke can be heard at a 
considerable distance, without some modifications in structure which 
would assist in increasing its efficiency for the purpose. 
Accordingly, we find that the bones are thicker and stronger than Page 358. 
in most birds, and there is only a slight movement possible of the 
upper jaw on the head proper. The interorbital septum is thick and 
nearly complete, supporting a median protrusion on the front of the 
skull, which is so considerable as to throw the free extremities of the 
hyoid bones one side or the other, thus causing the skull to be slightly 
unsymmetrical. Further, the axis of the upper beak is peculiarly 
low, being continuous with that of the basicranium ; and this results 
from the lowness in position of the points of junction of the superior 
processes of the premaxille with the frontal region of the skull, which 
renders the angle between the beak and skull less obtuse than is 
generally the case. 
In those birds in which there is considerable hinge-motion of the 
upper beak on the head, as in the Parrots, the basisphenoid rostrum 
is generally long and of uniform thickness for some distance, and the 
conjoined palatine bones, with the vomer between them and the 
pterygoids articulated behind, form a longitudinal flange along the 
upper service of the median junction, which runs backwards and 
forwards on the rail formed by the basisphenoid rostrum during the 
movements of the beak. In the Woodpeckers any considerable 
articulation of this kind would reduce the value of the head as an 
axe; consequently the posterior ends of the palatine bones are not 
well developed, and they scarcely ‘unite in the middle line, while 
further forwards the vomer is not seen in the maxillo-palatine region, 
and these latter bones also are only slightly developed. A similar 
tendency among Passeriniform birds to the reduction of the vomer in 
* “Ibis,” 1872, pp. 357-60. October 1. 
