45 
Bromaius 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 Bidus from the cursorial Brevipennates in this part of the skeleton. 
The ischia of the winged Pigeons resemble those of the Dodo; but the inner longitu- 
dinal ridge is more strongly marked in Bidunculus : in the Goura it is less developed 
than in Bidus ; the bone is longer also in proportion to its breadth, and the ischiadic 
foramen is longer and narrower : the proportions of that in Bidunculus are more like 
those in Bidus. In Bidunculus 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 diiferent 
members of the Dove-tribe. 
In comparing the pelvis of the Dodo with that of the Vulture (PI. XII. fig. 6), we 
find in the latter that the first two confluent sacral vertebrae 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 Bidus 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 vertebrae 
of the series, constituting a very marked difference, both as to number and the character 
of the vertebrae 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 Bidus 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 Bidus. 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 Bidus. In Otis 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 CEdicnemus 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 Bidus. In Eudyptes and Aptenodytes the ilia are more expanded ante- 
riorly, but the whole pelvis is narrower and longer than in Bidus. The Gar-fowl 
[Alca impennisy, JJria, 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 difier from those in the Dodo. Both the pros- and mes-en- 
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 diploe 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. Soc. vol. v. pi. 51. 
