CLASSIFICATION, AND PHYLOGENT OF THE DINORXITHID.^, 393 



* 



Its gently curved alveolar margins are marked, especially in Dinornis, with a broad, 

 shallow groove, and are continued horizontally inwards into a flattened ventral plate ; 

 from this is given off a strong ascending keel, formed posteriorly of paired plates, but 

 solid in front and gradually diminishing in height towards the tip of the beak. The 

 dorsal edge of the triangular vertical keel thus produced is expanded to form a pro- 

 minent median ridge passing behind into the nasal process and in front continued 

 more or less distinctly to the apex of the beak; this ridge is best developed in Dinornis, 

 in Emevs it is almost obsolete. The portion of the vertical keel included between the 

 ridge above and the ventral plate below has a triangular form, and is, as already stated, 

 bilarainar posteriorly ; it constitutes the frenavial septum (Owen), and is especially 

 well-marked in Dinornis ; the extremity of the ankylosed rostrum and mesethmoid 

 fits between its laminae. 



From the ventral plate of the body the thin, horizontal, palatine processes pass 

 backwards, diverging slightly so as to enclose a median palatine notch, through which 

 in the perfect skull (figs. 2 & 6) the anterior end of the vomer and rostrum are seen. 

 In Emeus the posterior end of the inner margin of the palatine plate gives oflF a some- 

 what pedate vomerine process (vo.pr.) which passes inwards and clamps the vomer ; 

 this process is small or absent in the other genera. The proportional length of the 

 palatine process and of the body of the premaxilla differs greatly in the various genera. 



From the posterior end of the alveolar margin of the body is given off the irregular 

 horizontally-riattened maxillary process, which extends backwards (figs. 3 & 7, mx.pr.) 

 dorsad of and in close contact with the anterior end of the maxilla, and ends close to 

 the base of the maxillo-palatine and immediately below the ventral end of the maxillo- 

 nasal. 



The nasal process is a flat plate extending backwards and upwards from the body 



to the front«-nasal suture, its posterior end lying, as already stated, in a shallow, 



parallel-sided groove, the premaxillary fossa, furnished by the mesial portion of the 



nasals. Its anterior or proximal end, where it joins the body of the bone, is slightly 



thickened in Dinornis, considerably thickened and somewhat triangular in section iu 



Anomalopteryx, Pachyornis, and Mesoj^teryx, greatly thickened and almost cylindrical 



in Emeus. 



c. The Maxitlo-jugal Arch. 



This consists of the usual three bones, the maxilla, jugal, and quadrato-jugal. 



The maxilla consists of two parts, a slender external and posterior portion, the 

 maxilla proper, and an irregular expanded antero-mesial portion, the maxillo-palatine 

 process (Plate LVII. figs. 6, 7, & 8, max.pal. ; Plate LXII. figs. 63 & 64). The 

 maxilla proper is a slender rod presenting a flat ventral surface, an oblique lateral 

 surface, a very narrow, smooth mesial surface, and a dorsal surface, to the whole length 

 of which the jugal is applied. 



The maxillo-palatine, in Dinornis, Pachyornis, Mesopteryx, and Anomalopteryx, is a 

 very irregular shell of thin bone, with a spacious cavity, the antrum, opening poste- 



