76 PROFESSOR OWEN ON THE 
Dromaius and Casuarius, yet the length of those foramina (which are unclosed) in 
Struthio and Apteryx, concomitant with the greater relative length of the pelvis, shows 
the difference of Didus from the cursorial Brevipennates in this part of the skeleton. 
The ischia of the winged Pigeons resemble those of the Dodo; but the imer longitu- 
dinal ridge is more strongly marked in Didunculus: in the Goura it is less developed 
than in Didus; the bone is longer also in proportion to its breadth, and the ischiadic 
foramen is longer and narrower: the proportions of that in Didunculus are more like 
those in Didus. In Didunculus the pubis coalesces with the ischium behind the small 
obturator foramen, but leaves a second or posterior elongate ischio-pubic vacuity. The 
greatest amount of resemblances with the pelvis of the Dodo is found in that of different 
members of the Dove-tribe. 
In comparing the pelvis of the Dodo with that of the Vulture (Pl. XXIV, fig. 6), we 
find in the latter that the first two confluent sacral vertebree supporting moveable ribs 
are succeeded by several with short abutting ribs, the extent of this part of the sacrum 
being nearly one-half of the whole, instead of one- -fourth as in Didus and the Doves. 
The reappearance of rib-abutments after four ribless sacrals is in the posterior third of 
the sacrum, and they are continued to the end of that bone from the last four vertebree 
of the series, constituting a very marked difference, both as to number and the character 
of the vertebra in the sacral part of the pelvis. 
With regard to the iliac bones, the anterior concave track occupies two-thirds of the 
extent of the bone in Vultur, not one-half as in Didus and most Doves ; the breadth of the 
posterior parts of the ilia with the intervening sacrum in the Vulture is relatively less 
than in the winged Doves, and differs in a greater degree from that characteristic part in 
the sacrum of Didus. In Ciconia the antacetabular part of the pelvis is relatively 
longer, and the iliac bones are more expanded anteriorly. In Platalea the proportions 
are more nearly those in Didus. In Ofis the ilia touch the fore part of the sacro-spinal 
ridge, but leave both posterior and anterior apertures of the ilio-neural canals widely 
open. In Edicnemus and Charadrius they are grooves, the ilia not reaching the sacral 
spines. The external concavity of the ilium is longer, narrower, and deeper, in most 
waders, than in Didus. In Eudyptes and Aptenodytes the ilia are more expanded ante- 
riorly, but the whole pelvis is narrower and longer than in Didus. The Gar-fowl 
(Alca impennis)', Uria, Podiceps, and Colymbus, all show still longer and narrower pro- 
portions of the pelvis. 
In the Doves of flight the proportions and relative position of the three compart- 
ments of the cranial cavity differ from those in the Dodo. Both the pros- and mesen- 
cephalic ones are proportionally larger than the epencephalic; and the mesencephalic 
compartment lies more directly below the prosencephalic one. A very thin stratum of 
finely cellular diploé divides the two tables of the skull along the medial line of the 
upper surface: it is thicker between the orbits. The falcial ridge at the inner surface 
* Trans. Zool. Soe. vol. v. pl. 51. 
