74 Transactions.—Zoology. 
foregoing vertebra, thus shewing that it belonged to a not quite adult 
individual; on the other hand, in the pelvis of H. assimilis the articular 
surfaces of these two last vertebrz are well anchylosed, and the junction of 
the parapophyses with the lower border of the ilia in its antacetabular part is 
also well accomplished, which is not quite the case in the pelvis of the larger 
species under review, so that we may safely assume that the former belonged 
to a full-grown mature specimen. 
The gluteal ridge is decayed in H. moorei, but is well developed and 
preserved in the smaller species, the gluteal process forming a rounded 
knob (g), which rises well above the pelvic disk, whilst in Aquila this process 
has а convex form, directed downwards, and standing well in advance of the 
ilia. Of the recent species Circus resembles most, in this respect, the extinct 
gigantic form. 
The pre-acetabular iliac plates unite about one-third from their anterior 
end above the summit of the sacral ridge, diverging again after having been 
united for 1:70 inch to form a small interposed neural expansion, anteriorly 
lying scarcely below the upper border of the iliac plates. In this respect it 
resembles Aquila, whilst in Hieracidea, and still more in Circus, the neural 
interposition is continuous all the way, but is narrowest in the region 
where, as observed, the iliac pre-acetabular plates meet in Harpagornis. 
The ischium is very strongly developed at the back part of the acetabulum, 
as might be expected in a bird of such great strength. The tuberosity of the 
ischium, a roundish flat process, 0-72 inch from its posterior termination, rises 
conspicuously above its lamelliform surface (&). The posterior termination of ` 
the coalesced ischium and ilium is not rounded off, as in Aguila, but has a 
rather acute form, which, of recent species, Circus, and still more conspicuously 
Hieracidea, also possess. 
The pubic bone, after forming the lower boundary of the obturator notch, 
gradually loses its trihedral shape and assumes a vertically flattened form, 
continuing to run for some distance parallel with the ischium ; however, as in 
both specimens its posterior portion is broken off, I cannot say how far it may 
have extended. In any case it is longer than in Aquila. 
A thin plate of bone, closely connected with the lower border of the 
ischium and gradually thickening, runs to the termination of that latter bone. 
At its beginning it forms the posterior boundary of the obturator foramen, and 
fills up the space between the ischium and the pubic bone. 
The subacetabular fosse (f), which are very shallow in Aguila and the 
Diurnal Zaptores now living in New Zealand, are deeply excavated. The 
pelvic disk is a strong bone separated on each side by a well-marked line from 
the hind part of the neurapophysial crest, which rises well above it, the latter 
showing, like all the rest of the bones of which the pelvis is formed, a 
