620 GEOLOGICAL SURVEY OF THE TERRITORIES. 
rior tibial artery, and is comparatively larger than usually seen in the 
Owls. Behind, the tendinal groove expands, and is bounded distally by 
the concave border formed by the trochlee. Upon its internal margin, 
just above the extremity of the bone, it shows an elongated but feebly 
marked depression of about 3 millimetres in length. This facet articu- 
lates with the os metatarsale accessorium, which is joined to the bone 
by ligament. This little bone in this bird has an average length of 4 
millimetres. It is twisted upon itself, and bears upon one border a con- 
vex, smooth surface for the tarso-metatarsus, while distally it has an 
articulating surface, resembling more the mid-trochlea than any other, 
for the proximal segment of the hallux. Above it is sharply grooved 
for the tendon that goes to that toe. The toes are four in number, and 
their bony segments follow the rule that governs the greater part of the 
Class Aves; that is, first, second, third, and fourth toes have 2, 3, 4, and 
5 phalanges allotted to them, respectively. The first phalanx of the 
hind toe is more compressed from side to side than in the other toes, 
possessing more of the characteristics of the second joints. Its posterior 
facet, that articulates with the accessory metatarsal, fits accurately into 
the cleft surface seen on that little bone. Anteriorly the facet has a 
median groove, forming two vertical convexities for the double concave 
facet on the claw, with its dividing ridge. The claws are alla good deal 
alike, varying in size, the rear one being the most compressed laterally. 
They are pointed, arched, and nearly conical, the horny thec that cover 
them during life only being grooved on the under side. Their proximal 
ends have an articulating facet for the next phalanx behind them; this 
is so arranged that they can be more smartly flexed than any of the 
other joints of the foot, due to the convex articulating surface extending 
well beneath on the phalanx they meet. On the under sides of their 
proximal extremities is a tuberosity for the attachment of the flexor 
tendons; it has on either side, below, an oval foramen to allow vessels 
and a nervelet to pass to the extremities of these ungual phalanges. The 
first joint of the second toe, and the first and second of the third, are 
thickest and short, articulating internally with the tarso-metatarsus, and 
having their facets so arranged as to allow of motion only in the one 
plane. These bones may almost be said to interlock with each other, 
with their superior projecting processes behind fitting closely into the 
deep groove intended to receive them on the anterior faces of the joints 
to their immediate rear. The other underscribed phalanges of these two 
toes resemble the proximal segment of hallux. The fourth or outside 
toe possesses five phalanges, but the three innermost segments are very 
short, and are really nothing more than one of the middle type of pha- 
langeal bones, such as the third on the mid-toe, divided into three nearly 
equal parts, the proximal and distal pieces retaining all the character- 
istics of that bone, while the middle segment is simply a mid-section of 
the shaft. This arrangement, however, together with the manner in 
which the proximal phalanx, if it may be termed so in this bird, articu- 
lates with the long and elevated trochlea on the tarso-metatarsus, gives 
this toe a versatility and a power to be thrown outward and, to a limited 
extent, to the rear, not enjoyed by any of the other toes, constituting one 
of the most interesting anatomical features that we find in the family 
Strigide. 
ee 
