68 T'ransactions.— Zoology. 
The shaft in its upper portion is considerably bent backwards, and very 
broad where it is attached to the tibia, after which it decreases rapidly in size. 
Two shallow pits for the insertion of tendons are well marked. 
METATARSUS. 
Harpagornis moorei. Pl. VIL, Figs. 5 and 6. 
The following are the measurements of this important bone :— 
Inches. 
Total length ... i > 9B 
Circumference at its paa dni, We анана ridges 
included  ... Ay cds sve ^ US 
Circumference at its distal «id A $e e. 28 
Cireumference of shaft where thinnest р 25-7190 
In its general form also, this bone resembles in its main features that of 
Aquila, except being somewhat more robust. 
The shaft at its upper end is expanded and transversely flat, gradually 
becoming narrower, and assuming towards its middle a trihedral shape, after 
which it flattens again above the fore and aft canal, between the middle and 
outer metatarsal, near their distal ends. 
In Circus the trihedral portion of the bone is much longer, even in 
comparison to its whole length, than either in the fossil bone or in Aquila. 
The form and position of the trochlear condyles agree more closely with 
Circus, they being broader and with a larger space between them than in 
Aquila. 
The tuberosity for the insertion of tibialis anticus is remarkably developed, 
another proof of the great power the fossil bird must have possessed. 
The ectocondylar concavity is well marked, far more than in the recent 
species, in both of which the outer side of the proximal surface is almost plane. 
The three tendinal grooves between the caleaneal processes and the inner 
posterior ridge are deeply excavated, much more than in Aguila audax. 
Half-way down the shaft they unite to form one concave channel, which, 
above and close to the process for the attachment of the metatarsal of the back 
toe, runs out to a flat surface. 
The two fore and aft foramina in the upper part of the bone, in the grooves 
near the base of the anterior intercondylar prominences, are well marked. 
The surface of the bone running from the outer margin of the ectocondylar 
ridge down to the outer condyle is very broad and flat, as in Aquila, having 
its greatest diameter in the middle portion of the bone, thus forming the base 
of its trihedral form. 
In Circus the base of the bone is situated more in its posterior portion, the 
ridge running towards the centre of the anterior portion of the shaft, giving 
the latter a triangular form for about two-thirds of its entire length. 
