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It is in this part of the skull that the Porphyrio (Pl. XLVII., fig. 2) most departs from 
the character of the Notornis (ib. fig. 8), the parieto-frontal region of the skull (fig. 2 
7,11) being convex and oblong. There are no such cerebral convexities in Notornis. 
The relative extent of the temporal fossa is greater than in any known existing bird, but 
it is shallow ; the Porphyrio makes the nearest approach to this character. ‘The optic 
foramina are blended together, and the orbits, as far as shown in the fossil, are small 
and ill-defined. The petrosal is proportionally large in the interior of the skull; its 
central depression (16, fig. 11) is narrow and deep, with an entry of an hour-glass 
form. The sinus or groove which extends round its fore-part is narrow and deep: 
the foramen ovale is large; the under surface of the frontals, at their coronal con- 
fluence is traversed by a median longitudinal groove, with a parallel broader depression 
on each side of it. The presphenoid has been of considerable depth; but its fore-part, 
together with the prefrontals, is broken away. 
The base of the upper beak, which was attached to the frontals, is a straight border 
(15, 22, 22’, figs. 8 & 9) ten lines in extent and half a line thick: the middle two-fourths 
is formed by the nasal process of the premaxillary (22’), a short linear fissure dividing 
this on each side from the nasals (15), the outer angles of which bend up. The bony 
base of the beak of Porphyrio presents a similar conformation (fig. 2, 15, 22’). The bony 
upper mandible of Nortornis is a long, inequilateral triangle, subcompressed, very 
slightly curved down ; with a quadrate oblique base (fig. 12), a smooth convex upper 
border, very gradually narrowing to the pointed apex ; the sides almost vertical ; the 
under (palatal) surface (22”, fig. 9) deeply grooved along the middle of its anterior half 
as far as this extends in the fossil; the groove deepening and widening to the single 
medial palatal opening (pl) of the nostrils. The alveolar borders are entire and sharp, 
with their inner sides slightly and obliquely grooved. In Porphyrio the palatal surface 
of the premaxillary presents a narrow ridge along the middle of its anterior half ; and 
the excavated surface on each side of this is continued to the sharp alveolar border. 
The external nostrils in both Notornis and Porphyrio are of a narrow ovate form, with 
the great end forwards and the long axis parallel with the upper slope of the beak ; they 
are perforated on each side near the base, quite in the posterior half, of the upper beak. 
They open into a common excavation at the base of this part, the lateral walls of which 
in Notornis are thin above and thick and cellular below, with two openings at the back 
of this cellular part leading into it (fig. 12). A thin transverse plate of bone (22’, fig. 12) 
rises from the lower and fore-part of the external nostrils, spans across the palatal 
nostril, and ascending perpendicularly with a slight curve backwards, closes the fore- 
part of the nasal chamber; there is no trace of bony septum dividing this chamber : 
the under surface of the nasal plate of the premaxillary is almost flat and smooth. 
The repetition of all the essential characters of this bony upper beak in the Por- 
plyrio (figs. 1, 2, 8) is so close, though diminished to the scale of one-half, as to 
preclude the necessity of reference to any other form of bird in the elucidation of the 
AA 
