PROFESSOR OWEN ON THE GENUS DINORNIS. 355 



one-sixth of a line, tiie fracture must have been close to the natural anterior termi- 

 nation of the bone ; which, therefore, would seem to have ended by a broad truncated 

 or slightly rounded border, and to have supported an upper bill, shaped like a cooper's 

 adze ; the whole upper bill being slightly and equably arched or curved downwards. 

 The total length of the premaxillary to the thin fractured end is five inches two lines. 

 In Didus the nasal branch of the premaxillary presents an elliptic transverse section 

 where it quits the maxillary processes, diminishes in depth as it retrogrades, becoming 

 depressed and broad where it rests upon and divides the nasals to anchylose with the 

 trontal. Where the nasal and maxillary processes diverge, there is a deep groove ex- 

 ternally terminating in a canal directed forwards into the rostral part or body of the 

 premaxillary. This part is subincurved, pointed, rough, and with irregular vascular 

 perforations, with a sharp inferior border on each side, and a more concave palatal sur- 

 face than in Dinornis. 



The palatal plate of the premaxillary in Dinornis extends one inch nine lines entire, 

 from the fractured end to the anterior border of the palatal orifice of the bony nostrils : 

 it is united to the upper plate by a strong median septum for about an inch and a half 

 of its anterior extent : a loose cancellous tissue fills the lateral spaces between this 

 septum and the lateral or bent-down plates : a rough low longitudinal ridge (r, fig. 1) 

 extends along the outside of these plates, and defines them from the upper surface at 

 the anterior part of the premaxillary. A well-defined rough alveolar border (s s, fig. 3) 

 extends backwards on each side from the premaxillary upon the coalesced maxillaries 

 («', 2i), and terminates by a slightly expanded portion below the anterior boundary of the 

 external nostril (indicated by the dotted line at n, fig. 1). These alveolar borders form 

 the sides of the shallow concavity on the palatine surface of the premaxillary. There 

 are one or two vascular or nervous foramina on each side of this surface with grooves 

 leading forwards from them ; and there are numerous vascular and nervous foramina 

 on the sides of the rostral part of the premaxillary (fig. 1 , 22). Although the maxillaries 

 have coalesced with the premaxillaries at one end and with the palatines at the other, 

 the anterior flattened ends of the latter are defined by hnear impressions, convex for- 

 wards, extending inwards from an angle of the thickened posterior end of the alveolar 

 border («'). The long and slender and almost straight palatines (20, figs. 1 & 3) are concave 

 below, slightly so at their fore-part, but deepening as they pass backwards by the bending 

 down of their outer and still more of their inner border : this part coalesces posteriorly 

 with the vomer, which there unites together the two palatines, bounds with them the 

 palatine nostril posteriorly, and is then continued forward in the middle line, dividing 

 the back-part of the palatine nostril. Here the vomer contracts, but how it terminates 

 anteriorly is not shown, the anterior end being broken off; it is grooved above where it 

 supported the cartilaginous nasal septum : ossification has extended a little way into 

 this septum from the middle of the under surface of the nasal process of the premax- 

 illary (15', fig. 3). The narrow alveolar process of the maxillary, continued backwards 



3 c2 



