368 PROFESSOR OWEN ON THE GENUS NOTORNIS. 



It is in this part of the skull that the Porphyrio (fig. 2) most departs from the character 

 of the Notornis, the parieto-frontal region of the skull (7, n) being convex and oblong. 

 There are no cerebral or hemispheric convexities in Notornis, The relative extent of 

 the temporal fossa is greater than in any known bird ; the Porphyrio makes the nearest 

 approach to it. The optic foramina are blended together, and the orbits are remarkably 

 small and ill-defined. The petrosal is proportionally large in the interior of the skull ; 

 its central depression (i6, 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 confluence, 

 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 

 (i5, 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 true 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 beak of Notornis 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 blunt-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 

 median palatal opening (pi) 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 slender 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- 

 phyrio (figs. 1, 2, 3) 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 

 aflinities of Notornis. Yet the form, so magnified, is so novel and unexpected, that 



