172 MR. W. P. PYCRAFT ON THE MORPHOLOGY AND 
The paroccipital processes pass gently forwards at their base into the zygomatic 
process, in all save in the Tinamous and Apterya, Rhea, and Dinornis. In Apteryx and 
the Tinamous they are separated from the zygomatic process by a notch more or less 
deep. In Dinornis they pass forward into the squamosal prominence, and there lose 
themselves. In Rhea only, externally, they are continued upwards as a strong ridge to 
join the posterior boundary of the temporal fossa, and, internally, sweep round towards 
the middle line in the form of a thin, curved, laminated plate of bone to form the inner 
boundary of the tympanic recess. 
The Roof of the Cranium (Pl. XLII. figs. 1-4).—The roof of the cranium is 
produced laterally, in front of the temporal fossa, into a pair of pendent post-orbital 
processes, in all save Apteryx and the Crypturi. In the former, post-orbital processes 
are entirely absent, and in the latter they are reduced to a mere prickle. The anterior 
region of this roof, in all save Dinornis, Afpyornis, Apteryx, and Crypturi, is charac- 
terized by a pair of very long outstanding and backwardly-directed spines, being the 
elongated supra-orbital process of the lachrymal. In Struthio these are continued 
backwards, by means of fused supra-orbital ossicles, to join the frontals ; thus enclosing a 
space between the ossicles and the combined frontal and nasals (fig. 8). 
In Dinornis the lachrymal passes backwards insensibly into the frontal to form a 
broad overhanging ledge to the orbit. In the Crypturi it projects conspicuously on 
either side of the skull, but is without the backwardly-projecting spines. In Apteryx 
the lachrymal has become reduced to a mere vestige fused with the alinasal. 
In all save Apterya and the Tinamous the frontal is produced laterally to form an 
overhanging pent-house to the orbit. In Apteryx, the frontal passes downwards and 
inwards in the form of a smooth convex infolding of the bone, leaving the orbit without 
any sharply defined boundary ; and in the Tinamous this region is deeply hollowed out, 
almost to the middle line, so that the interorbital region of the skull is very narrow. 
Young skulls of Rhea and Dromeus resemble the Tinamous in this respect. 
There is a conspicuous cerebral dome in Apyornis and Dromeus ater. In profile, 
in Dromeus ater, the skull slopes rapidly downwards and forwards in front of this dome; 
in Apyornis the gradient is much less marked. 
The inter-orbital region in Dromeus is very wide, in Rhea very narrow: thus, taken 
in connection with the development of the supra-orbital processes of the lachrymals, 
this forms a useful character for systematic purposes. 
In the Tinamide the frontals bear shallow supra-orbital grooves. 
The Buse of the Skull (Pl. XLII. figs. 5-8).—Casuwarius, Dromeus, Struthio, and the 
Tinamide all agree, more or less closely, in the form of the basitemporal platform. In 
all, viewed below, it takes the form of a flattened, slightly tumid area, roughly penta- 
gonal in shape, the base being caudad. Its postero-lateral angles are not produced into 
mammillary processes, nor are there, save the Eustachian apertures, any sharply defined 
boundaries forwards. Struthio and Dromeus somewhat closely resemble one another 
