xv, i Shufelclt: The Monkey -eating Eagle 53 
the mounted specimen at the United States National Museum, 
so that no comparison can be made here along such lines with 
the corresponding bones in our subject. In the latter the bone 
has a length of about 12 centimeters and an average breadth 
of 2 centimeters. Its summit exhibits two shallow articular 
facets for the condyles of the tibiotarsus. An intercondylar 
tubercle stands between them on the anterior margin, the width 
of the surface being double its depth, while posteriorly is to 
be noted a hypotarsus of the usual aquiline type. This consists 
of a quadrilateral process standing out at right angles to the 
bone — its hinder border being considerably thickened — and its 
base opposite the inner articular concavity at the summit. Op- 
posite the outer one is another process, it being stumpy and 
much aborted; between the two is a wide, shallow valley. 
Posteriorly the shaft of this tarsometatarsus is smooth, broad 
above, and somewhat narrower distally. It is concaved through- 
out its entire extent, its margins being more or less sharpened, 
except where the accessory metatarsal is swung by ligament 
about a centimeter above the inner trochlea. The outer aspect 
of the shaft is flat, being broad at the middle third, and taper- 
ing somewhat to the ends. It is the posterior margin of this 
surface that forms the inner sharpened border of the posterior 
aspect alluded to above. Anteriorly the surface is much twisted 
upon itself, the upper half being concaved longitudinally and 
convexed.for the rest of the extent, the t^vo merging into each 
other. At the upper third, anteriorly, we note the usual twin 
perforations a short distance below the summit; and below 
them, to the outer side, is the elongate tubercle for muscular 
insertion. 
Distally there are three very substantial trochleas for the basal 
phalanges of the toes, the inner one being the largest and at 
the same time the lowest on the shaft. Slightly up on the shaft, 
between the outer and middle condyle, is to be noted the usual 
foraminal perforation present in nearly all birds; it transmits 
the flexor tendon of the outer toe and, it is said, the anterior 
tibial artery. 
The accessory metatarsal is of considerable size, is flattened 
and somewhat twisted upon itself, and supports distally a very 
large, transversely disposed, trochlear facet; the latter is devoted 
to the articulation of the basal joint of the hallux, which is 
a digit of enormous power and strength, as will be appreciated 
through a glance at Plate N. Equally powerful are the joints 
and the talons of the anterior toes, the arrangement and pro- 
