236 MR. W. P. PYCRAFT ON THE MORPHOLOGY AND 
In Struthio the femur, as in Dromeus, is highly pneumatic, and, as in Dromeus, 
bears a large pneumatic fossa between the head of the femur and the great trochanter. 
The shaft is relatively much thicker than in Dromwus or Cassowary, and the fibular 
condyle is much larger than the inner tibial condyle. ‘The groove dividing them is also 
narrower and deeper than in Dromeus. 
The tibio-tarsus, apart from its greater size, is peculiar in the relatively smaller 
size and hooked form of the ectocnemial crest, and the great length of the fibula, 
which extends to within a short distance of the upper border of the proximal tarsal 
mass. The extensor groove is shallow. Furthermore, the lateral borders of the 
posterior trochlear surface are produced backwards and upwards into a pair of 
proximal ridges at right angles to the long axis of the shaft. 
The tarso-metatarsus is of course at once distinguishable by the absence of ento- 
trochlea. It is grooved anteriorly, and bears a pair of foramina dorsad of the scar for 
the tibialis anticus. 
The ungual phalanx of the outer toe is represented by a small nodule. 
In Rhea the femur is non-pneumatic. It may be at once distinguished from that 
of any other Palwognathe by the great depth of the popliteal fossa. 
The tarso-metetarsus resembles that of Struthio in the feeble development and in 
the form of the ectocnemial crest and in the backward projection of the condyle of 
its distal extremity. The femur falls far short of the level of the tarsal mass. The 
tarso-metatarsus has a shallow groove anteriorly, a deep fossa above the scar for the 
tibialis anticus, and a very broad and low intercotylar process. ‘The hypotarsal keel 
lies to the inner side of the median line. In Dromeus and Casuarius it is median in 
position. 
The 1st phalanx of digit 1. is conspicuously lengthened, the 2nd is very short; 
of the tv. digit the proximal phalanx is long, the 2-4 very short. 
In Apterya the femur is relatively large and more slender than in any other living 
Paleognathe, save the Tinamous. It is non-pneumatic, and the popliteal fossa is 
deep. 
The tibio-tarsus proximally is broad and flattened from back to front, neither the 
ecto- nor procnemial crests are much developed. The extensor groove is deep. The 
intercondylar gorge is deep, and the ento-condyle of great size. 
The tarso-metatarsus is shorter than the femur, much flattened from back to front ; 
the intercotylar tubercle is well marked; there is a fossa above the scar for the tibialis 
anticus; the 2nd and 4th trochlee are widely separated from the meso-trochlea. The 
hypotarsus bears a pair of low median ridges. 
There are four digits. The digits contain no conspicuously shortened or elongated 
phalanges, and therein differ from the other Palwognathe herein described. 
In Dinornis the femur is relatively much shorter and thicker than in Struthio. Its 
distal end is of great width; the intercondylar gorge is very wide and shallow and 
