92 Prof. R. Owen on the Solitaire. 
thereto. The action of the outer beam upon the maxillary is 
conjoined with that of the lower beam upon the premaxillary 
by the overlapping broad palatal plate of the maxillary, 
which is more or less confluent with the palatine and pre- 
maxillary bones beneath. 
The movements of the mandibular part of the bill are 
transferred by the long bar-like rami of the lower jaw to the 
lower end of the tympanic, with which those rami are movably 
articulated by a combined double ball-and-socket and also 
trochlear articulation. 
When the tympanics are swung forward they communicate 
that motion by their six converging bony bars to the upper 
and lower cores, raising the former, depressing the latter—in 
short, opening the mouth. When the tympanics swing back- 
ward, opposite movements are transferred forward by the con- 
necting bars, and the beak is shut. 
But when in this state it is used (as by the Woodpecker) as 
a pick or wedge, the strength of the blow transferred back- 
wards by the three divergent pairs of bars is met, not by a 
rigid basis, which might have involved fracture of those bars 
or of some of them, but by a yielding one, as in the butts with 
elastic buffers terminating a railway line, for arresting and 
receiving the shock of a train. 
The beak as a whole, and especially its outward and visible 
portions, have suggested to ornithologists characters of groups 
with good and accepted descriptive terms ; the modifications 
of a part of the mechanism, a single beam, seem inadequate to 
sustain a new nomenclature. 
The basisphenoid (PI. VIII. fig. 2, 5) in advance of the 
ridge or process which underhangs the bony outlets of the 
Eustachian tubes loses breadth and seems narrowest where 
impressed by the abutting ends of the pterygoids (21). 
The postarticular end of the mandible of Dedus differs from 
that in most Columbide in not being abruptly truncated, but 
produced in the form of a short right, or rather open, angle 
with the apex obtuse*. That of Pezophaps (Pl. VII. fig. 1) is 
more columbaceous; it is produced a short way behind the 
articulation, and is vertically truncate, without loss of depth. 
It agrees in this respect with Didunculus. 
There is nothing extraordinary in the conformation of the 
pelvis of Pezophaps. The acetabulum is situated in the ante- 
rior half, as in Didus. The ischium (Pl. VII. 63) coalesces 
with the ilium (2) at two points, circumscribing a moderate 
* ‘Dodo and its Kindred,’ pl. viii.; ‘Memoir on the Dodo,’ pl. i. 
