PHYLOGENY OF THE PALZOGNATILE AND NEOGNATH. 203 
In Rhea the nasal must be regarded as holorhinal, though the maxillary process is 
absent. Inasmuch as this process, when present, serves as the boundary, caudad, of 
the anterior nares, its place must be regarded as being filled by a vertical spike of bone 
arising from the maxillo-palatine process to the anterior border of the lachrymal. In 
Struthio this vertical spike—in [hea separating the anterior nares from the lachrymo- 
nasal fossa—is represented by a ligament which is attached dorsad to the free end of 
the maxillary process of the nasal. 
In Struthio the nasal is holorhinal (Pl. XLII. fig. 5). Its maxillary process is 
well developed, and continued downwards on the maxillo-palatine by ligament. 
The Zinamidw may be regarded as holorhinal, though the nasal cleft has extended 
backwards so far as to lie level with the free end of the nasal process of the premaxilla. 
The maxillary process is not wanting as in Ehea, though reduced to a mere vestige. 
The nasal cleft is bounded externally by a vertical, bony rod, representing the 
maxillary spike found in Rhea. It differs therefrom in being rod-like, very slender, 
and is perfectly free. Above, it articulates, by means of a short inturned process, with 
the anterior border of the lachrymal and the vestigial maxillary nasal process, whilst 
ventrally it articulates with the extreme postero-external border of the maxiilo-palatine 
process where it joins with the rod-shaped portion of the maxilla. This vertical rod 
was regarded by Kitchen Parker as the maxillary process of the nasal. It is, however, 
in all the skulls I have examined, quite distinct from this. 
The Jachrymal, in Dromeus, sends backwards a very long, curved, rod-like process 
to overhang, and thereby greatly increase the size of the orbit (Pl. XLII. fig. 2). It 
sends downwards a large antero-posteriorly flattened limb, the outer border of which 
is produced still further downwards into a short rod-like spine which articulates with 
the quadrato-jugal bar. The body of this ventral process of the lachrymal is perforated 
by a large foramen for the passage of the lachrymal duct. ‘The inner border of this 
ventral process articulates with the antorbital plate. 
In Casuarius the lachrymal differs from that of Dromeus in the greater relative 
shortness of its external orbital process, which is scarcely longer than the internal. A 
further point of difference lies in the fact that the external orbital process passes 
insensibly forwards and downwards into a laterally compressed plate, which, after 
forming the boundary caudad of the posterior narial aperture, turns sharply backwards, 
and becomes the antero-posteriorly compressed ventral process bounding the lachrymo- 
nasal fossa as described in Dromeus. From this it differs in that the laminated portion 
is continued downwards to the level of the quadrato-jugal bar, instead of stopping short 
of this, and sending downwards thereto a spine from its outer border. The foramen for 
the lachrymal duct is smaller than in Dromeus. Internally it articulates with the 
antorbital plate. 
In Rhea the lachrymal resembles that of Dromeus. ‘The supra-orbital process is 
large. ‘The lachrymo-nasal process is also antero-posteriorly compressed, ‘Ihe foramen 
