Prof. R. Owen on the Solitaire. 89 
phaps, rather more than half that of the skull; in Didus it is 
little more than one third. 
The difference is not due to the small relative size of the 
orbits, but to the great relative length of the beak, especially 
of the narial part, in Didus. This part, which includes the 
lateral bony external nostrils, is relatively shorter m Pezo- 
phaps than in Didus. 
The interorbital septum is entire in both genera. 
In both Didus and Pezophaps the upper grooved border of 
the foramen magnum extends further back than the condyle. 
The occiput, in Pezophaps (Pl. VII. fig. 2), is vertical, feebly 
convex vertically and transversely, divided by a pair of 
arched insertional depressions from the rugose, somewhat 
overhanging hind tract of the parietal region (ib. 7). The 
temporal fossa is larger, relatively and absolutely, in Pezo- 
phaps than in Didus; it resembles that of Treron. The 
elevation of the frontal region is due, in Pezophaps, as in 
Didus and Treron, to excess of bony cellular diploé, and 
takes place in advance of the orbits in all Columbide. The 
interorbital tract of the cranium (Pl. VIII. fig. 1, 1) rises 
from the premaxillo-nasal platform (ib. 15, 22) more abruptly 
in Pezophaps than in Didus; but it sooner subsides, and the 
fronto-parietal tract, or vertex, is flatter. This tract is smooth, 
but surrounded by a broad rugose elevated border, continued 
from the superorbital ridge backward over the temporal fossa, 
then across the postparietal region (ib. 7) to meet the ridge 
on the opposite side. The superorbital tracts converge for- 
ward to form the frontal convexity. This, however, is 
mesially cleft, exposing a deeper-seated smooth tract, over 
which a bony fringe projects on each side. This structure 
exists in a minor degree in the female. The superorbital 
tract is more rugose in the male than in the female Pezo-. 
haps. 
The chief difference between Didus and Pezophaps in cra- 
nial structure is the degree in which the cancellous tissue is 
developed between the outer and inner “ tables,”’ the minor 
quantity of that tissue in Pezophaps causing less elevation 
and convexity of the frontals above the orbits as compared 
with that part of the cranium in Dedus. 
The lacrymal, coalesced with the prefrontal part of the 
frontal, curves down and back in front of the orbit; it is 
impressed by a deep, wide, smooth longitudinal channel exter- 
nally, conducting the duct to the naso-lacrymal orifice ante- 
rior to the orbit. 
To view the neurapophyses of the nasal vertebra, the nasals, 
premaxillary, and coalesced part of the frontals must be 
