74 Transactions. — Zoology. 



foi-egoing 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 vertebraj 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 a 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 resjiect 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 Aquila., 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 j)ubic bone. 



The subacetabular fossae (f), which are very shallow in Aquila and the 

 Diurnal Raptores now living in ISfew 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 



