292 MR. W. K. PARKER ON THE OSTEOLOGY OF BALZNICEPS REX. 
region. In the latter non-typical birds, e.g. Dromaius and Rhea, the process is obsolete 
which in ordinary birds descends from the nasal to the maxillary; and in Rhea the 
broad single nasal process of the coalesced pre-maxillaries is unusually short, being 
succeeded by the nasals, which here meet at the mid-line for some distance, divaricating 
again as they pass, narrow and splint-like, between the large lacrymals. This meeting 
of these bones along the mid-line is very exceptional in birds; yet they really do 
approach each other more nearly than would appear from a casual view of the matter. 
In such birds as the Pigeon, the thin splint-like mesial and lateral processes form but 
a small part of the bone, which, higher up, becomes cellular, meets its fellow, and 
forms a large mesial oval part of the forehead, pushing the narrow anterior portions of 
the great sphenoido-frontals aside. In birds with very cellular foreheads,—e. g. the 
Owls (Strix, Ulula, Asio, &c.), the Balearic Crane (Grus pavonina), the Woodcock 
(Scolopax),—the thin tips of the pre-maxillaries pierce the bone of this frontal region, 
wedging themselves in between the roof-bones and upturned centrum of the anterior 
sphenoidal cincture. But the nasals do more than this—they lose their lath-like cha- 
racter, and help to form the rich diploé of this region, most of which is contributed by 
the sphenoido-frontals. Generally in birds these ethmoidal roof-bones may be distin- 
guished more easily than most of the elements of the upper surface of the head, if we 
except the lacrymals ; and in several Struthious birds, Galline birds, and Rails, they 
continue pretty distinct throughout life, whilst in a great proportion of species traces of 
the sutural lines are persistent. This character, combined with their thin, fibrous, 
elastic condition, makes them very traceable. But this is not always the case; for in 
birds with a dense, close skull-wall, e. g. Parrots, Hornbills, Toucans, and Balzniceps, 
—and even with a cellular skull, as in the Podargus,—the traces of composite structure 
in these regions are most of them entirely obliterated. In most typical birds, the nasal 
either overlaps, pushes aside, or passes under the great frontal (its successor), becoming 
more or less anchylosed with it: anteriorly it splits or bifurcates, the upper process 
passing along the inferior and outer margin of the nasal process of the pre-maxillary, 
whilst the lower process passes downwards and forwards to join the palatal process of 
the maxillary and the maxillary itself. The extreme degree of coalescence which has 
taken place in this somewhat immature skull of the Baleniceps makes it impossible to 
point out the boundaries of the nasals ; but some large skulls of the Common Duck 
scarcely half a year old, in which the sutures are still very evident, and the skull of 
the Heron will give a good idea of the relations and extent of this bone. The Adjutant 
(Leptoptilus), moreover, even in old age shows the sutural lines in this region, in rows 
of canals and passages, just as the facial extent of the lacrymal of Balzniceps is shown. 
In the latter bird, the width of the bone in front of the great cranio-facial hinge is 
barely two inches ; in the former it is slightly above that measurement, and yet the width 
is not eked out by the lacrymals as in Baleniceps. The nasal processes of the pre- 
maxillaries in the Adjutant are each half an inch wide at the hinge, the nasals being of 
