276 MR. W. K. PARKER ON THE OSTEOLOGY OF BALANICEPS REX, - 
In Baleniceps, as in the great Maccaws, the orbital margin of the frontal is higher (in 
the former ith of an inch) than the mesial part of the bone; and this marginal elevation 
in both kinds subsides gently into the slightly concave upper interorbital surface of the 
frontals. In the Maccaws and in the Baleniceps, the highest part of the cranium is 
between the post-frontal processes ; and in the latter the shape of the cranial cavity is 
in some degree marked out on the external table of the frontal and parietal bones. 
The orbital margin of the frontal (or, as Professor Goodsir calls it, the sphenoido- 
frontal) in Baleniceps is, as is usual in this class, more or less notched or perforated 
by vessels. In the Boat-bill and in the Heron, the large eye-ball has elevated the 
orbital margin of the sphenoido-frontal ; but this takes place most in the latter, in which 
bird the concavity between these margins is unusually deep. 
In the rough, unevenly convex cranium of the Adjutant, the orbital margin is nearly 
half an inch below the mid-line of the frontal. 
In Baleniceps, a gentle ridge of bone, arising from the posterior edge of the post- 
frontal process (figs. 1,3, 6, pf) passes upwards and backwards to the distance of about 
two-fifths of an inch from the mesial line of the skull in the parietal region, and to one- 
third of an inch in front of the epiotic eminence. This gently curved ridge is the 
anterior boundary of the temporal fossa (Pl. LXV. figs. 1 & 3, ¢f), which is subtrian- 
gular in shape, and has for its posterior margin a line, nearly at right angles to its 
anterior boundary, which line runs outwards, downwards, and backwards, losing itself 
in the ridged crest of the upper mastoid eminence. The inferior margin of the tem- 
poral fossa is incomplete in front, there being a large semi-oval space between the 
post-frontal process and the articular surface of the base of the squamosal for the 
external condyle of the head of the os quadratum. Behind this external quadrato- 
squamosal facet a rough ridge of bone runs horizontally across, losing itself in the 
fossa between the upper mastoid eminence and the ‘ par-occipital’ ala; this ridge 
defines the temporal fossa below and behind. 
These fossz are ten lines apart in Baleniceps; in the highly arched head of the 
Adjutant they do not meet by two inches; the distance of these fossz in Buceros bicornis 
is one inch and four lines, in the Maccaw one inch and six lines; and in the Pelican 
they do not approximate more than in the Maccaws. 
But in many birds, e. g. the Heron, Boat-bill, Podargus, Diver (Colymbus), and the 
larger Grebes (Podiceps), the temporal fosse are only separated by a sharp interparietal 
crest, whilst their anterior and posterior boundaries are almost parallel. ‘This is like 
what obtains in many other vertebrata, the extreme conditions of this sagittal ridge 
being found in such fishes as the Ephippus, Pagellus, and Platax arthriticus ; in the Cha- 
meleon amongst the reptiles ; and, in the mammals, in such skulls as those of the Tiger, 
Hyena, and certain Bats, e. g. Molossus obscurus. 
The post-frontal process of the Baleniceps is strong, and descends downwards, and 
also slightly outwards and forwards, its length being eight lines. The end of this 
