CLASSIPICATION, AND PHTLOGENT OF THE DINOfiNITHID^. 419 



Body of piemaxilla narrow and pointed ; its length rarely and its breadth never 



more than length of basis cranii. 

 Maxillo-palatine contains a large antrum. 

 Nasal has a slender maxillary process {qu. except in Anomalopteryx, where there is 



a distinct maxillo-nasal bone I). 

 Mandibular symphysis pointed ; its width always considerably less than three fourths 



of length of basis cranii. 

 Length of mandible nearly always less than four times that of basis cranii. 



Genus Pachtornis. 



Occipital plane vertical or slightly inclined backwards ; occipital crest prominent ; 



supraoccipital fossae well marked ; anterior and posterior lambdoidal ridges enclose 



a wide lozenge-shaped area. 

 Paroccipital process short, bluntly pointed. 

 Width of cranium at paroccipital processes from one and a half to nearly twice 



length of basis cranii. 

 Width at squamosals more than double length of basis cranii. 

 Cranial roof strongly and evenly arched ; an irregular shallow depression at base of 



postorbital process. 

 Mamillar tuberosities large. 

 Margin of tympanic cavity evenly curved. 

 Temporal fossa large; distance between temporal ridges about one and a third 



times width of cranium at temporal fossae; width of temporal fossa about three 



fourths length of basis cranii ; mid-temporal ridge small or absent. 

 Temporal and lambdoidal ridges may or may not be in contact. 

 Posterior temporal fossa narrower than in Dinornis and Anomalopteryx, but wider 



than in Mesopteryx and Pachyornis ; inferior temporal ridge strong ; pretympanic 



process short. 

 Zygomatic process long, bluntly pointed. 

 Margin of orbit rather sinuous ; postorbital process angled, consisting of horizontal 



and descending portions. 

 Distance between optic foramina about one half length of basis cranii, 

 Antorbital very thin ; supraorbital fenestra moderate ; postchoanal bar strongly 



curved outwards and forwards and more prominent than in any genus except 



Dinornis. 

 Rostrum broad and flattened in about its posterior 15 mm., then moderately com- 

 pressed as far as the triangular processes, where it becomes broad and rounded 



below (the anterior extremity is lost in all the specimens 1 have examined). 



