inter-condylar fossa is well marked; the ecto-condvlar fossa is 
moderately large, and very deep. 
Tibio-Tarsus.—This bone is 171 mm. long', with a proximal 
width, including the head of the fibula, of 2<j mm. The anterior- 
posterior dimensions of the same, amount to .26 mm. Proximally 
the pro-cnemial crest rises to 5 mm. above the floor of the con¬ 
tained fossa, and the ecto-cnemial crest develops a hamular pro¬ 
cess. A large number of foramina penetrate the shaft within 
the first 50 mm. of its length, and during dissection blood con¬ 
tinued to ooze from 13 such apertures. This enormous amount 
of vascular penetration into the substance of the shaft, as well 
as the extent to which all the muscles of the leg are supplied 
with blood vessels, must relate to the need for power in striking 
the natural prey of the bird, and the sustained drain upon the 
muscular power during the transit of the prey across long dis¬ 
tances. 1 he shaft of the bone is gradually flattened out as it 
approaches its distal extremity, the measurements in the centre 
being 12 mm. in diameter x 10 mm. in thickness, as against 15 
mm. x <S mm. immediately above the extensor bridge. The 
proximal half of the shaft is bent backwards, and twisted out¬ 
wards. by which latter modification the ankvlosed fibula de¬ 
scribes an arc of a circle ; this is in marked contrast to the 
almost straight tibio tarsus and fibula of the vulture. Distally 
both condyles are developed to an almost similar degree (the 
ecto-condyle being the smaller). The extensor bridge is 5 mm. 
wide, and is set at an angle of 70 degrees to a line drawn ver¬ 
tically through the centre of the shaft. 
Fibula.'—The fibula : s free proximally, but ligamentously 
articulated by the head; then follows an open space 15 mm. 
long and 3 mm. wide; next an ossified tract 40 mm. long, suc¬ 
ceeded by a second space 25 mm. long; lastly, a well ossified 
tract of 40 m'm., after which the bone subsides upon the shaft 
of the tibia. A large nutrient foramen is situated immediately 
above the second space between the two bones. The head of 
the fibula measures 26 mm. x 7 mm. 
1 arso-Metatarsus.—This hone is 118 mm. long, 22 nun. 
wide proximally, and 27 mm. distally. Owing* to the even de¬ 
velopment of the condyles of the tibio-tarsus, as already noted, 
the articular cups show less disproportion in size than usual, and 
are almost upon the same level; that for the ecto-condyle is the 
larger and deeper of the two. There is a single tubercle for 
the attachment of the tibialis anticus. having a face of 8 mm. 
long. Unlike the similar attachment in the leg of the chestnut¬ 
faced owl, there is no tendency to form here a semi-ossified 
bridge. The two foramina, at the proximal end of the bone, 
left for the transmission of blood vessels through the shaft, are 
