PROFESSOR OWEN ON THE GENUS DINORNIS. 353 



short rough antorbital process (o) , and continued posteriorly into a long and broad com- 

 pressed postfrontal (12) which descends and curves back to coalesce with the mastoid. 

 The upper surface of the frontals presents two feeble convexities (fig. 2), slightly indi- 

 cating the cerebral hemispheres ; and anteriorly has coalesced with the prefrontals 

 (u, fig. 5), the nasals (is, fig. 3) and the premaxillary (22'). The expanded upper surface 

 of the coalesced prefrontals (tig. 5, u) is covered by the naso-maxillary base of the 

 upper bill (is, 22'), but is separated from it by a shallow interspace. In Otis the inter- 

 orbital part of the frontals is deeply and widely excavated. In Didus the frontals are 

 broad and convex, rising singularly above the cranial ends of the nasals and premax- 

 illary, with which they also coalesce. The supraorbital plate presents a rough notch 

 near the fore-part, where in Dinornis there is a shallow emargination. In Dinornis 

 there is a shallow depression with vascular grooves at the outside of the base of the 

 postfrontal, distinct from the temporal fossa, whereas in Didus the temporal fossa 

 extends forwards above the postfrontal and forms there a reniform depression, either for 

 a gland, or, what is less likely, for a coextension of the origin of the temporal muscle. 



Of the vomer there is a portion of the narrow anterior end (is, fig. 3) which has 

 coalesced with the palatines (20) and is grooved as usual above. Below the plate formed 

 by the coalesced frontals, premaxillary and nasals, there is a distinct thin plate of bone 

 formed by the coalesced prefrontals (u, fig. 5j, which are continuous with the antorbital 

 processes of the frontals (a, a), a deep notch indicating the limits of the two bones on 

 each side. The prefrontals form two olfactory chambers, each of the size of a French-bean 

 (fig. 5, 18, 18), smaller therefore, proportionally, than in the before-described crania of 

 Palapteryx, and also more advanced in position. A single olfactory foramen opens into 

 the back-part of each chamber, which also communicates by a larger lateral perforation 

 (6, fig. 1) with the fore-part of the orbit. From each side of the coalesced prefrontals, 

 an antero-posteriorly compressed angular process (u', figs. 1 & 5) extends outwards and 

 downwards, bounding the orbit anteriorly : this process is perforated (e) at its base, and 

 the olfactory chamber is continued upon a concavity at its fore-part (fig. 5) : it does not 

 answer to the position and connections of the lachrymal in other birds, but rather to 

 that process which in many birds, the Bustard (fig. 8, 14'), Owls, e. g., is developed from 

 the fore-part of the interorbital septum, extends outwards and commonly coalesces with 

 the lower end of the true lachrymal. The continuation of the presphenoid and orbito- 

 sphenoid with the prefrontals makes a complete bony interorbital septum in the Dinornis ; 

 but this is slightly swollen and cellular only at its anterior part, and not wholly, and to 

 the enormous extent which characterises it in Apteryx and Didus. Although the nasals 

 (15, fig. 2) have coalesced with the nasal process of the premaxillary (22') as well as with 

 the frontals (11), their form and extent are indicated by linear grooves on both the upper 

 surface of the frontals and the under surface of the nasal plate of the premaxillary 

 (is', fig. 3) : they are broad, convex and slightly raised at their base, where they are 

 separated from each other by the premaxillary ; converge and pass beneath the pre- 



VOL. III. PART V. 3 C 



