Hague (Netherlands). Conférence Internationale sur.

Proceedings / Linnean Society of New South Wales, Sydney, Volume 18 online

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extremity of the sternum is four-notched, two on either
side, the outer notches being the deeper. Both have rounded
bases, and the processes that separate them are ample and possess
rounded extremities. The border upon which the keel ends poste-
riorly is square, though we have met with specimens in which it was
slightly notched in the median line. The body is oblong, and if
we include the xiphoidal processes on either side, has a length half
as long again as its width. The ventral and convex surface, like
the dorsal, is smooth and presents but two points for examination.
The pectoral ridge, faintly marked throughout its extent, originates
on each side at a point near the outer borders of the coracoid
grooves, running inward and backward, and dies away at the base
of the keel near its middle. This little ridge denotes the line be-
tween the pectoralis major and minor. The keel is moderately
well developed, the distance from the base of the manubrium to the
carinal angle being equal to the distance from the same point at
the base of the manubrium to the base of either costal process or
outer anterior sternal angle. It is compressed, smooth and thin,
but its stability is greatly aided by the carinal ridge on either side,,
which commences strong and well-marked at the base of the manu-
brium, just within the anterior border, running parallel with the
latter, and disappears as it approaches the carinal angle. The ante-
rior border of the keel is sharp and concave ; the inferior border
is convex, with the edge slightly thickened. The point of inter-
section of these two borders anteriorly 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 VertebrcB and Coccygeal Vertebrce, — In the sacrum of the

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Owl now under consideration, with the exception of a few faint
lines indicating the original individuality of the vertebrae, these
bones are thoroughly anchylosed together and to the ossa innomi-
nata. From inspection of this compound bone in immature birds
we find the usual number of sacral vertebrae composing the sacruoi
to be thirteen. The anterior face of the first possesses all the ne-
cessary 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 below to the inter-
spinous h'gament. The neural canal is circular and the prezyga-
pophyses well marked. The articular facet of the centrum is in
the vertical plane, with its curvatures similar to those ascribed to
the anterior facet on the centra of the dorsals. The neural spines
are broad and the transverse processes are strong and raised, with
their enlarged extremities expanded upon and firmly united
with the iliac bones. There is but one pair of sacral ribs, and they
are free ones. Long and slender, they articulate with the first
vertebra in the usual manner, but the relation is much more inti-
mate, as they touch the diapophyses for some little distance
beyond the tubercula toward the capitula. The lower extremities
of these ribs are terminated by little roundish knobs, which articu-
late with the corresponding sternal rib on either side, described
above as being inserted in the posterior border of the fifth sternal
rib. Viewing the bone dorsal-wise, it is to be seen that the thick-
ened 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 back-
ward, is firmly wedged between the ilia until we pass the third ver-
tebra ; 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 millimetres of
each other. The sacrum completely fills in the lozenge-shaped
space thus formed from the third vertebra — first, by continued
broadening and compression of the neural spine, that soon becomes
one with the others of the series ; and secondly, by the expanded
extremities of the di- and parapophyses, the processes themselves
also taking due part. The integrity of the surface is unbroken,
save posteriorly, where a few pairs of foramina exist among the ex-
panded transverse processes, increasing in size from before back-
ward. Anterior to a line joining the acetabula the surface is in the

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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 a majority of
both the diurnal and nocturnal Rapiores. The *' ilio-neural" canals
here present open but small apertures posteriorly at about the point
where the ilia commence to diverge, passing obliquely downward
and forward ; their anterior openings are large enough to allow a
view of their internal walls. The neural spine that divides them
throughout is compressed from side to side ; the ilia which form
their outer boundaries are convex ; the neuro-spinal crest forms the
roof, the basal surface being deficient, formed merely by the spine-
like di- and parapophyses of the Vertebrae and the confluent neural
arches. Now, a line drawn mesially on the centra below, from
the first centrum to the last, gradually rises until opposite the
anterior borders of the ischiadic foramina, then curves rather
abruptly downward to its termination. The centra of the first
two or three vertebrae are compressed from side to side to such
an extent as to cause them to appear wedge shaped, the com-
mon apex or edge being below ; after that, however, they rapidly
broaden, become compressed vertically and more cellular in
structure. They are very broad from the fourth to the ninth, inclu-
sive, then as rapidly become contracted as they approach the
coccyx. Minute but numerous pneumatic foramina are seen at or
near the usual localities. The largest foramina for the exit of the
roots of any pair of sacral nerves is generally in the fifth vertebra ;
they decrease in size as they leave them either way. In the young
only the last few of these foramina are double ; they are all double
in the adult, and placed one above another, a pair on the side of
each centrum at their posterior borders. The tranverse processes
of the anterior five sacral vertebrae are thrown out against the inter-
nal surfaces of the ilia, to which they are firmly attached, and act
as braces to hold the engaged bones together. The parapophyses
of the first form facets for articulation with the sacral ribs; the sec-
ond and third have none ; in the fourth and fifth they also act as
braces in the manner above described, joining the ilia just before
their divergence commences. Reliance seems to have been placed
entirely in the completeness of the sacro-iliac union in the last ver-
tebrae, for the apophysial struts terminate in that portion of the
pelvic vault formed by the sacrum itself, except in the last two ver-
tebrae, where the parapophyses abut against the iliac borders. The

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parapophyses of that vertebra which is opposite the acetabula are
prominent, they being long and ample, reaching to the border and
reinforcing that part of the pelvis that requires it the most, the
vicinity of the leverage for the pelvic limbs. In other Strigidce
several apophyses are thrown out at this point. The posterior
opening of the neural canal in the last sacral vertebra is subcircular,
its diameter being about a millimetre in length. This vertebra also
possesses small postzygapophyses, looking upward and outward for
articulation with the prezygapophyses of the first coccygeal vertebra ;
the articulating facet of the centrum is also small, long trans-
versely, notched in the median line, the surface on either side
being convex. At every point where the sacrum meets the iliac
bones union is firm and complete, though both upon the internal
and external surfaces the sutural traces are permanently apparent.
The anterior iliac margins, as they diverge from the sacral spine,
form an acute angle, concave forward ; they have a well-marked
rim or border, nearly a millimetre in width, raised above the gen-
eral surface of the bone, which disappears on the outer borders as we
follow them backward. The two anterior and outer angles overhang
the sacral pair of ribs and fifth or last dorsal pair. From these last
the marginal boundaries, which necessarily give the bones their
form, are produced backward and outward to a point opposite the
centrum of the third sacral vertebra, then backward and inward,
forming at the above points two lateral angles. From the apices of
the two lateral angles to where the borders terminate on either
side in front of the acetabula with the pubic bones, the direction is
such as to form a concavity on each side ; the line adjoining the
bases of these concavities, points opposite the posterior openings of
the ilio-neural canals, being the narrowest part of the pelvis. The
upper and at the same time the inner margins of the bones in ques-
tion form the anterior and median angle at first approach, soon to
diverge from each other and form the gluteal ridges and borders
of those scale-like projections of the posterior portion of the ilia
that overhangs the acetabula. Produced now as the "gluteal
ridges," they tend almost directly backward, though very slightly
inward, to terminate in the ischial margins. The preacetabular
dorsal iliac surfaces are generally concave, while the postacetabu-
lar, and at the same time that surface which occupies the higher
plane, is flat, having a sloi)e downward and backward, with a ven-
tral reduplication after forming the rounded and concave posterior

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boundary of the pelvis. The preacetabular superficial iliac area is
nearly double the extent of the postacetabular. The antitrochan-
terian facets that surmount the cotyloid cavities have the usual
backward direction, though their surfaces look downward, outward
and a little forward. The external surfaces of the ischia look upward
and outward, having just the reverse direction ventrally. Poste-
riorly these bones are produced beyond the ilia into finely-pointed
extremities, tending to approach each other. The slender pubic
bones, after closing in the obdurator foramen on either side,
touch and unite with the inferior borders of the ischia as far as the
. pointed ends of the latter, beyond which they are produced nearly
to meet behind. The circular and thoroughly perforated acetabula
are formed in the usual manner by the three pelvic bones. They
have a diameter of about three millimetres, and their circumfer-
ences are in the vertical plane. The ischiadic foramina are ellipti-
cal and large ; they are, as usual, posterior to the acetabular and
above the obdurator foramina. These last are also elliptical and
about one-third the size of the others. Viewing the pelvis ven-
tralwise, we observe, in addition to points mentioned when speak-
ing of the sacrum, the reduplication of the ilia, forming pockets
behind and internally, that open outward through the ischiadic for-
amina and inward into the general pelvic cavity. The narrowest
part of the pelvis measures 1.2 centimetres, the widest 2 centi-
metres, being taken between the iliac projections over the ace-
tabula; the average length, including anterior neural spine, is 3 cen-
timetres. Pneumatic foramina occur in the shallow anfractuosities,
between the antitrochanters and gluteal ridges in the ilia. None
of the caudal vertebrae are grasped by the pelvis, the posterior ex-
tremity of the sacrum always assisting to form the posterior pelvic
border. The usual number of these vertebrae is seven, though oc-
casionally an additional one is found, making eight in some indi-
viduals. This enumeration does not include the modified and ulti-
mate coccygeal vertebra, the pygostyle. They are all freely mova-
ble upon one another, and the first upon the last sacral vertebra.
The articular facets upon the centra vary in shape throughout the
series ; that upon the first is long transversely, with a double con-
vexity so arranged as to accommodate itself to the one on the ex-
tremity of the sacrum ; they soon become uniform, to pass to the
subcircular one existing between the last vertebra and the pygo-
style, on which it is concave.

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The pleurapophyses and parapophyses are very rudimentary or
entirely suppressed. Each vertebra bears a prominent neural
spine, which, from the first to the sixth, inclusive, is bifurcated ;
in the last two it appears as a mere primitive knobule. The trans-
verse processes are all deflected downward and outward, very
small in the first and still more so in the last ; are largest in the
fifth and sixth. Prezygapophyses are well marked ; they reach for-
ward and articulate with the feebly developed postzygapophyses.
In a few of the posterior segments there appears to be an effort on
the part of the neurapophyses to overlap the vertebra next beyond
them. The neural canal is pervious throughout, commencing in .
the first with a calibre equal to that in the end of the sacrum ; it
gradually diminishes and terminates in a minute, blind conical
socket in the pygostyle. Hypapophyses are produced downward
in a few of the ultimate vertebrae. They hook forward and articu-
late with the centrum of the vertebra next beyond them. Some-
times they are observed to be free, or rather resting upon a facette
on the anterior margin of one centrum and extending over to the
anterior margin of the centrum of the vertebra anterior to it, to
meet a similar facette, as a tiny styliform process. The spinal col-
umn is completed posteriorly by the pygostyle — that ploughshare-
shaped segment that articulates with the last coccygeal vertebra.
Above its cup-shaped facet this bone arises as a laterally com-
pressed plate, extending backward and bifurcated at its extremity,
as if to imitate the neural spines of the vertebrae of the series of
which it is an ultimate appendage. Below the facet it projects
forward and completes the median sequence of hypapophyses of
the centra, being rather larger than any of them. The posterior
curve is simply inflected downward and forward from its apex.

The Scapular Arch, — The three elements that constitute this
arch are all represented, and all independent or free bones ; the
coracoids articulate with the sternum and scapulae ; coracoids and
clavicle, connected by ligaments, lend their share to form or
strengthen the shoulder-joints. The coracoid, comparatively large
and strong, forms in the usual manner an arthrodial joint of
restricted movement with the sternum, its lower end being in the
coracoid groove on the anterior part of that bone. The inner
angle of its base is about two millimetres from the mesial line, and
four millimetres intervening between it and its fellow of the oppo-
site side in the groove. This extremity is broad, its outer angle

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being beneath the third sternal rib at its point of meeting the cos-
tal border ; it is compressed from before backward. The articu-
lar facet, looking downward, backward and a little inward, is
transversely concave, with a slight dividing ridge running antero-
posteriorly, converting the general concavity into two smaller
ones. The coracoid, when in position, is produced upward, for-
ward and outward, making, with the vertical line through its
base, rather an acute angle. A limited portion of the middle
third of the bone only is subelliptical on section and at all shaft-
like, due to the fact that the coracoid in this bird being perhaps
less than the average length as compared with the size of the bird,
and, secondly, to the unusually enlarged extremities, features
observable, more or less, in Raptores generally. The anterior
groove of the upper extremity, that is arched over by the head of
the clavicle above, is deep and occupies fully the upper third of
the bone. The coraco-clavicular process springs, thin and com-
pressed, from the inner side of the shafk of the bone, at junction
of upper and middle thirds, to turn upon itself, so as to be pro-
jected upward, forward and a little outward, terminating with
an elliptical facet for articulation with the clavicle. The upper
border of this process is concave lengthwise and articulates
throughout its extent with the inferior margin of the acromial
process of the scapula. The lower and thin edge of the coraco-
clavicular process tends obliquely downward, to be lost on the
inner surface of the shaft of the bone near its middle. The outer
wall of the anterior groove is formed by the coracoid itself, the
process just described being really nothing more than a wing-like
extension forming the inner boundary of the groove in this bird ;
it terminates above both clavicle and scapula in a rounded tuber-
ous head. Below this head, anteriorly and still more inwardly, the
coracoid affords a vertical, elongated facet for the clavicle, while
behind, looking a little outward, is the concave elliptical facet that
constitutes about one-third of the glenoid cavity for the humerus.
Internal to this last, and running first directly upward, then mak-
ing a right angle and continuing forward, a little upward and out-
ward, the last direction being the upper margin of the coraco-
clavicular process, is another facet, for the scapula. Behind and
below, this bone displays one or two lines and depressions, bounda-
ries of muscular attachments. In the middle of the anterior
groove, opposite the base of the coraco-clavicular process, the

PBGC. AMBB. PHIL08. 80C. XXXIX. 164. TT. PBINTBD JAN. 19, 1901.

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shaft of the bone is perforated ; this perforation is elliptical length-
wise with the shaft and passes directly through to make its appear-
ance on the posterior convex surface just below the scapula. This
foramen transmits a branch of that cervical nerve coming from
between the twelfth and thirteenth cervical vertebrae. This nerve
branch, after passing through the bone, is distributed to the under
surface of the pectoralis minor muscle, and its filaments ascend
among its fibers. This foramen is observable also in other Owls,.
as Bubo virginianus, and in some of the diurnal Rapiores^ as in
Accipiter cooperi ; in very many birds it is absent. This scapula
presents little that is unusual in that bone among the class gener-
ally. It lends the additional two-thirds of articular surface to
form the glenoid cavity with the coracoid; internal to this the
acromion process extends forward, touching the coracoid as de-
scribed and having a limited bearing on the clavicle. Posteriorly
its blade-like length is produced, expanding, turning slightly out-
ward, to terminate in an obliquely truncate extremity, with its
point over the second dorso-pleurapophysial interspace.

What the scapula lacks in interest is amply made up by the
changes observed in the last bone of the group, the clavicle. This
element is broad above, much compressed from side to side
throughout ; it spans the anterior groove and touches the scapula
as described above, rapidly diminishing in size as it is produced
downward and inward by a gentle curve toward the fellow of
the opposite side. The upper extremities in adult birds are separ-
ated by an average distance of 2.3 centimetres. If the sternum
pointed to feebleness of flight in this little Owl, it is still further
carried out by the ill-developed clavicles, which constitute that
arch in birds when they are thoroughly and firmly united below,
that assists to resist the pressure of the humeri when the wings are
depressed in flight, and send them back to their former position after
the completion of the action. In an old male Speoiyio^ we find this
bone to be simply a pointed styliform process. In other individu-
als, however, and adults, too, the clavicle does not even attain to the
length there shown ; but, as if to bid defiance to any invariable rule
governing its development, we again find in very young birds cases
where it becomes confluent with its fellow, forming a broad
U-shaped arch, though never a very strong one. In a case of this
kind the bone was finely cancellous throughout, with an extremely
attenuated layer of compact tissue outside, scarcely covering it.

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In the figures given in my memoir on Speotyto and other indi-
viduals like it, the clavicles were pneumatic. Again, in both
young and old, it may have any of its lower parts completed by
cartilage ; it never displays a* mesial expansion of bone at the
point of confluence. As already shown, the superior entrance of
the anterior groove on the coracoid is a complete circuit, formed
by the three bones of the group. The head of the coracoid over-
hangs it above ; next below is the clavicle, closing it in anteriorly ;
lowest of all the scapula behind. A plane passing through the
superior margins of this aperture would look upward, inward and
backward. All the bones of the scapular arch are pneumatic,
with the exception sometimes seen in the clavicle ; and the
foramina, to allow the air to enter their interiors, look into the
enclosed groove of the coracoid just described. In the scapula
the foramen is usually single and in the acromion process ; single
again in the clavicle, it is seen in the broadest part of the head,
while in the coracoid there is generally a group of these little aper-
tures, situated in the depression on the surface that overhangs this
entrance to the coracoidal groove.

As in many others of the family, in common, too, with not a few
of the diurnal Raptoresy this Owl possesses an os humero scapulare,
of the usual form, that increases the articular surface of the
shoulder-joint for the humerus.

Of the Upper Extremity, — The upper extremity consists of ten
distinct bones in the full-grown bird, omitting minute sesamoids
• that may possibly exist. These are the humerus of the arm, the
radius and ulna of the forearm, two free carpels, the metacarpal
and four phalanges. The humerus is a long, extremely light and
smooth bone, and when viewed from above in its position of rest,
with the wing closed, it reminds one of the curve in the small
italic letter/, being concave above toward the scapula. And this
bone is so twisted that this same curve is exhibited, though not
quite as well marked, when viewing it laterally. The humerus is 5.5
centimetres long, subcylindrical on section at midshaft, at which
point a minute aperture exists for the passage of the nutrient ves-
sels that are distributed to the osseous tissue and its internal lining.
This foramen enters the bone very obliquely, its external orifice be-
ing nearest the proximal extremity. This end is well expanded, and
surmounted above by a strongly developed radial crest that over-
hangs the shaft slightly toward the palmar aspect. It occupies a

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line on the bone from the articular facet for the shoulder-joint to a
point one-third down the shaft. The ulnar crest, or lesser tuber-
osity, encloses quite an extensive fossa below, which acts also as a
partial screen to the pneumatic foramina, for the humerus is highly
pneumatic. These foramina usually consist of one circular open-
ing, surrounded by a group of many smaller ones. In young
birds a very large foramen is generally present ; this closes in as
age advances. Between the two tuberosities is the vertical and
elliptical convex facet for articulation with the glenoid cavity of
the shoulder- joint, constituting the ** head of the humerus." The
radial crest displays palmad, a ridge for the insertion of the tendon
of the pectoralis major. The distal end of the humerus is also ex-
panded in the vertical plane and gently convex anconad — the re-
verse condition of the proximal extremity. It presents for exam-
ination the articular facets for the ginglymoid joint it forms with

Online LibraryHague (Netherlands). Conférence Internationale surProceedings / Linnean Society of New South Wales, Sydney, Volume 18 → online text (page 65 of 68)