66 T'ransactions.—Zoology. 
species was also very powerful Of the latter the linea aspera is not quite 
continuous, being repeatedly interrupted at more or less considerable intervals. 
The form of the proximal orifice is somewhat different from that of H. moorei, 
it being more rounded ; however, this may be a sexual or even individual 
peculiarity, and of no specific value. 
Examining the femora of a male and a female Circus, I observe that this 
proximal orifice in the larger female is also oval, and in the smaller male more 
rounded off. 
I have already alluded to the probability that the portions of the two 
skeletons of extinct birds under consideration might belong to the male and 
female of the same species, owing to a resemblance in their principal 
osteological features and to the great disparity of size of many of the recent 
Diurnal Raptores. 
In order to illustrate this more fully, I would suggest a comparison of the 
femora of Circus assimilis of both sexes, both belonging to full-grown and 
mature birds, obtained under similar conditions. 
Certainly, if these two bones had been found in a fossil state, one would 
not deem it expedient to place them in the same species, owing to their 
remarkable difference in size. 
TIBIA. 
Harpagornis moorei. Pl. VII., Figs. 1 and 2. 
Inches 
Total length : vd 9:52 
Circumference at ipana]. iid ix Т .. 548 
Circumference at distal end : oe ... 4°60 
Circumference of shaft where ылын 2:22 
The same pachydermal character, if I may di express myself, 
distinguishes also this bone, like all those of the posterior limb of this gigantic 
species, from any bird of prey known to inhabit New Zealand at present. 
Even in comparing the same with that of Aquila audax, of Australia, with 
which it has otherwise many features in common, this character is well 
exhibited. 
The form of the surface of the proximal end agrees wellin both species, 
with the exception that the proximal ridge is more rounded off, and the 
intercondylar tuberosity stands higher in Zarpagornis,in which two features 
the fossil bone agrees more with Circus. 
Two narrow and low intermuscular ridges are well marked, the first of 
which begins at the base of the procnemial process and extends to the inner 
side of the extensor tendinal canal, above the bony bridge spanning over the 
precondylar groove; the other at the termination of the vertical fibular ridge, 
descending the shaft in a transverse line till it has crossed two-thirds of its 
