xv, i Shufeldt: 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 two 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 trochlea? 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 X. Equally powerful are the joints 

 and the talons of the anterior toes, the arrangement and pro- 



