SHUFELDT.] OSTEOLOGY OF THE SPEOTYTO. 613 
birds cases where it becomes confluent with its fellow, forming a broad 
U-shaped arch, though never a very strong one. In a ease of this kind 
the bone was finely cancellous throughout, with an extremely attenuated 
layer of compact tissue outside, scarcely covering it. In Pl. I, and 
other individuals like it, the clavicles were pneumatic. Again, in "both 
young and old, it may have any of its lower parts completed by carti- 
lage; it never displays a mesial expansion of bone at the point of 
confluence. We believe in the Barn Owl (Aluco) it anchyloses with 
the sternum at the carinal angle, by its bending backwards and meet- 
ing it at its lowest and median point. 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 
overhangs it above; next below is the clavicle, closing it in anteriorly ; 
lowest of all the scapula behind. <A plane passed through the superior 
margins of this aperture would look upwards, inwards, and backwards. 
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 inclosed groove of the coracoid just de- 
scribed. In the scapula the foramen is usually single and in the acro- 
mion 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 apertures, 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 Raptores, this Owl possesses, particularly the older individuals, 
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 might ex- 
ist. These are the humerus of the arm, the radius and ulna of the fore- 
arm, two free carpals, the metacarpal, and four phalanges. (See Pl. L.) 
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 re- 
minds one of the curve in the small italic letter Ws being ¢ concave above 
towards 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 mid- 
shaft, at which point a minute aperture exists for the passage of the 
nutrient vessels that are distributed to the osseous tissue and its inter- 
nal lining. This foramen enters the bone very obliquely, its external 
orifice being nearest the proximal extremity. This end is well ex- 
panded and surmounted above by a strongly developed radial crest 
that overhangs the shaft slightly towards the palmar aspect. It occu- 
pies a line on the bone from the articular facet for the shoulder-joint to 
an extent shownin Pl. I. The ulnar crest, or lesser tuberosity, incloses 
quite an extensive fossa below, which acts also as a partial screen to the 
pneumatic foramina, for the humerus is highly pneumatic. They usu- 
ally consist of one circular opening, surrounded by a group of many 
smaller ones. In young birds a very large foramen is generally pres- 
ent; this closes in as age advances. Between the two tuberosities is 
the vertical and elliptical convex facet for articulation with the glenoid 
eavity 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 reverse 
