700 SHUFELDT— OSTEOLOGY OF THE STRIGES. [Deenv5 
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 Raffores, as in 
Accipiter coopert ; 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 Sfeoty/o, 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 ruie 
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. 
