710 SHUFELDT—OSTEOLOGY OF THE STRIGES. (Dec. 7, 
seen at this end of the tarso-metatarsus ; one just at the external 
termination of the bony bridge mentioned above, and the other 
outside and a little above it. Their posterior openings are immedi- 
ately behind the anterior ones, or, in other words, they do not 
pierce the shaft in any way obliquely. The shaft of this bone is 
notably square on section for the major part of its extent, being 
encroached upon, however, both before and behind, by the afore- 
said tendinal grooves. The tendons, especially those that occupy 
the posterior canal, are very prone to ossification, forming quite 
sizable bones in the adult, the largest of these being equal to the 
fibula in bulk, exclusive of course of the head of that bone, and not 
being as long. Returning to the tarso-metatarsus, we find at its 
distal extremity, for examination, the trochleze that articulate with 
the rear segment of all the toes except hallux. Viewing this end 
with the bases of these trochlez toward one, we find the general 
outline made by them to be crescentic, with the horns having a 
tendency to approach each other behind. ‘The outer trochlea is the 
highest and longest from before backward ; the other two are about 
on the same level, the inner one having a posterior and internal 
process, while the middle one is possessed of a median cleft travers- 
ing its face antero-posteriorly. They are sharply divided from each 
other by narrow slits that extend up as far as the articulating part, 
and are continued on the anterior aspect of the shaft for a short 
way as delicate groovelets. A foramen is situated in the outer of 
these that gives passage to the antcrior tibial artery, and is com- 
paratively larger than is 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 three millimetres in length. This 
facet articulates with the os metatarsale accessorium, which is joined 
to the bone by ligament. This little bone in this bird has an aver- 
age length of four millimetres. It is twisted upon itself, and bears 
upon one border a convex, 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 joints follow the 
rule that governs the greater part of the class 4ves—that is, first, 
second, third and fourth toes have two, three, four and five pha- 
— —-_ 
