608 GEOLOGICAL SURVEY OF THE TERRITORIES. 
anterior sternal angle. Itis compressed, smooth, and thin, but its sta- 
bility is greatly aided by the carinal ridge on either side, which com- 
imences strong and well marked at the base of the manubrium, just 
within the anterior border running parallel with the latter, and disap- 
pears as it approaches the carinal angle. The anterior border of the 
keel is sharp and concave; the inferior border is convex, with the edge 
slightly thickened. The point of intersection of these two borders an- 
teriorly is rounded and forms the carinal angle. The inferior border 
expands posteriorly, and the keel terminating a short distance before 
‘ arriving at the posterior sternal border, the two become blended with 
the surface of the body of the bone. 
Sacral vertebre ; pelvis; and coccygeal vertebre.—In the sacrum of the 
Owl now under consideration, with the exception of a few faint lines in- 
dicating the original individuality of the vertebra, these oones are 
thoroughly anchylosed together and to the ossainnominata. From in- 
spection of this compound bone in immature birds, we find the usual num- 
ber of sacral vertebrae composing the sacrum to be thirteen. The anterior 
face of the first possesses all the necessary elements for articulation with 
the last dorsal. The neural spine has a thickened crest that soon meets 
the ilia on either side ; its anterior edge is thin, and gives attachment be- 
low to the interspinous ligament. The neural canal is circular, and the 
prezygapophyses well marked. The articular facet of the centrum is in 
the vertical plane, with its curvatures similar to those ascribed to the an- 
terior facet on the centra of ‘the dorsals. The neurapophyses are broad 
and the diapophyses are strong and raised, with their enlarged ex- 
tremities expanded upon and firmly united with the iliac bones. There 
is but one pair of free sacral pleurapophyses; these are long and 
slender, articulating with the first vertebra in the usual manner, but 
the relation is much more intimate, as they touch the diapophyses for 
some little distance beyond the tubercula towards the capitula. The 
lower extremities of these ribs are terminated by little roundish knobs, 
which articulate with the hemapophysis on either side, described as 
being inserted in the posterior border of the fifth sternal rib. View- 
ing the bone dorsal-wise, it is to be seen that the thickened crest of the 
neural spine of the first vertebra protrudes from the angle made by the 
ilia meeting it anteriorly to a greater or less distance. This broad and 
compressed crest, then continued backwards, is firmly wedged between 
the ilia until we pass the third vertebra; at this point the ilia diverge from 
each other to another point just anterior to the acetabula, then converge, 
terminating in the posterior sacro-iliac border within five or six milli- 
metres of each other. The sacrum completely fills in the lozenge-shaped 
space thus formed from the third vertebra—first, by continued broaden- 
ing and compression of the neural spine, that soon becomes one with the 
neurapophyses; and, secondly, by the expanded extremities of the di- and 
par-apophyses, the processes themselves also taking due part. The in- 
tegrity of the surface is unbroken, save posteriorly, where a few pairs of 
foramina exist among the expanded transverse processes, increasing in 
size from before backwards. Antericr to aline joining the acetabula this 
surface is in the horizontal plane ; posterior to this line there is a decline, 
which declination is accepted also by the innominate bones; this gives 
the entire pelvis a shape that seems to be characteristic of the majority of 
both the diurnal and nocturnal Raptores. The “ilio-neural” canals, here 
present, open by small apertures posteriorly, at about the point where 
the ilia commence to diverge, passing obliquely downwards and for- 
wards; their anterior openings are large enough to allow a view of their 
internal walls. The neural spine that divides them throughout is com- 
A a 
