171

147

The praetrochanterian ridge (Pl. CVII. fig. 2, h) is linear, and may be traced down the
middle of the fore part of the shaft ; its continuation into the antentocondylar ridge (n)
is interrupted. This ridge, as well as the antectocondylar ridge ( ib. ib. m) , is well
marked, and relatively sharper than in Aquila. The rotular channel is broad and deep.
The popliteal space (ib. fig. 1, z) is shallow. The distal end of the femur is relatively
broader transversely than in Aquila. The intercondular ridge (ib. fig. 4, t') is well
marked. The backward production of the inner condyle dividing the tibial facet (ib.
ib. x) from the fibular facet (y'), is relatively more produced and sharper. Every cha-
racter of the femur indicative of muscular force and strength of joint is better marked
than in the smaller existing Raptorial birds, although inferior, especially as regards the
posterior ridges of the shaft, or 'lineae aperae,' to that bone in the huge objects of prey
of the Harpagornis ( Pls. XX.-XXIII). the least circumference of the femoral shaft
in the larger (female?) Harpagornis is 2 inches 6 lines, in the smaller (male?) specimen
2 inches 3 lines. The admeasurement in the Table, as in the subject in Pl. CVIII.,
is from the larger specimen of the extinct bird of prey.

Tibia. - This bone in Harpagornis corresponds with the femur in its strength, i.e. in
the proportions of breadth to length of shaft.

The procnemial ridge (Pl. CVII. figs. 5 & 6, g) is more produced at its upper part
than in the Eagles, but sooner subsides into the lower less prominent ridge (ib. fig. 6, g'),
which is continued down the fore part of the shaft, inclining toward the innermost of
the distal condyles. The Depression on each side of the procnemial ridge is well
marked ; the inner (tibial) one (ib. fig. 6, l) is bounded by the low, thick, obtuse
'entocnemial' ridge (ib. ib. o) extending from the overhanging inner (tibial) border of
the proximal articular facet of that side of the head, obliquely downward and forward
to join or be lost in the procnemial ridge. The outer depression (ib. 5. 5, k) has the
form of a wide vertical channel, and is bounded externally (fibulad) by the extocnemial
process (ib. ib. h). The fibular ridge (ib. fig. 5, m, m') is well marked ; it is relatively
more prominent, but is of minor longitudinal extent, than in the Eagles. The ectar-
ticular convexity is smoothly rounded ; the rugous facet anterior to it for the 'crucial'
ligament, and that attached to the head of the fibula, are well marked. The two distal
condyles (ib. fig. 5, t, s) show a breadth which exceeds by two fifths that of the same
part of the leg-bone in the Condor or Lammergeyer. In their proportions, shape, and
degree of anterior convexity these condyles exhibit the Falconine characters of this end
of the tibia. The praecondylar groove (ib. ib. p) is crossed by the osseous bridge (q'), as
in the Diurnal division of Raptores. The strength of the 'tibialis anticus" muscle
(p. 61, Pls. XI., XIV. s, Apteryx) is significantly indicated by the size of the bony canal
which was traversed by its tendon.

In the metatarsus (Pl. CVII. figs. 5, 6) of Harpagornis the indications of the power
of the raptorial foot reach their maximum. This will be evident to any one comparing
the above figures with those of the metatarsus of the Golden Eagle (Aquila chrysaetos).

x