Skull. Pl. XI.
What remains of the skull is well preserved, every process being sharp and distinct, as in a freshly-macerated specimen, but unfortunately the following appendages have been lost:—the quadrate, jugal, pterygoid, and lachrymal bones. The shape of the head, including the lower jaw, and allowing the usual proportion for the quadrate, would have been:—Height, two-thirds the length; transverse diameter, one-half the length.
The brain-case is short, high, and compressed laterally, its posterior-inferior diameter being greatest. The nasal portion of the skull, which is distinctly shorter than the cranial, is detached; and the mobility of the upper mandible, which in such birds is usually effected by the flexibility of the thin nasal bones, must, if it existed, have been effected by a straight joint with thick, irregular margins, somewhat as in the parrot.
In the occipital region the muscular ridges are moderately developed. The
condyle (oc) moderate, reniform, flattened, and excavated above, with a mesial notch, slightly excavated beneath, but not laterally.
The foramen (Fm) is very large, being one-third the height of the occiput in its vertical diameter, which is one-fourth greater than the transverse. It is rounded above, but has the lateral and inferior margins almost straight. The occipital area is rather square in form, with a blunt mesial ridge (So), having a shallow pit (a) on either side, but no fontanelles. A bold par-occipital process (po) extends downwards and backwards on each side, and forms the extremity of the cranium in that direction, giving rise to the most remarkable feature in its external conformation as viewed laterally. A deep perforated pit (b) separates this process from the basi-occipital, which is very largely developed, and has two inferior lateral processes (l) separated by a wide, smooth, sub-condylar notch (c), and then extends forward as a broad, slightly-concave surface, which occupies a large area at the base of the skull (br). The basi-sphenoid (Bs) has a small share in the base of the skull, and has large oval basi-pterygoid facets (bp) only slightly divergent.
The character presented by the tympanic fossa is very remarkable, as it is divided into a posterior and anterior portion by a quadrate ossicle (ms) that connects the tip of the mastoid process with the basi-occipital and with the anterior process of the ex-occipital, thus enclosing a wide canal descending obliquely backwards and outwards, with a sub-circular aperture deeply notched inferiorly. The articular portion of the tympanic fossa, with its two facets, is thus separated from the posterior or auricular portion, a character which appears to be unique. *
The frontal bone (F) is slightly swollen at the vertex and depressed between the orbits, which have strong overhanging orbital processes, on which are rough, deeply-impressed areas (d), which probably gave attachment to a posterior development of the cere of the mandible, these impressions being separated by a smooth groove with only a faint mesial ridge. There appears to have been a deep notch (d′) in the upper part of the orbital border, but the lachrymal bones having been lost this is not very clear. The width of the nasal suture (Fn) is equal to the length of that for the attachment of the lachrymals (Fl), which extends from the glandular groove to the transverse suture. The inter-orbital septum is complete, and there are well-ossified rhinal chambers (Rh). The roof of the orbit is flat, and with a very slight granular groove. The optic foramen is at the posterior and inner angle of the orbit, directly above the front of the basi-pterygoid facet. Behind the post-orbital process is a deep imperforate pit. The brain cavity extends for 6 lines anterior to the optic foramen. The upper mandible has all its elements completely fused; the large nostrils (e) occupy more than half of the superior sloping area, their
[Footnote] * I have since found it, but less marked, in Cereopsis.
aperture being directed outwards, forwards, and upwards, rounded in front and angled behind, and they are separated by a smooth bony interspace (f) which is one-fourth the width of the mandible. The tip is rounded, with a tumid area for the attachment of the horny mandible, the length of which is equal to the width. Interiorly the palatal plate is flat, with deeply-incurved borders, notched on each side of the tip, and deeply excavated by a longitudinal groove (h), which is perforated by two well-defined apertures, the one (h′) large and directed upwards, the other (h″) small, directed backward in a line with the groove. The palatines are firmly united with the vomer, the upper surface of which has a slight groove to receive the pre-sphenoid.
The lower mandible is stout, but broad and compressed in every part, the rami preserving a lamellate structure throughout, and being united by a broad symphysis (sy), the length of which is equal to one-fourth of the mandible, the anterior half being flat and the posterior excavated. Inferiorly the punctate surface of attachment of the horny mandible covers the whole of the symphysial portion.