418 PEOF. T, JEFFEEY PAEKEK ON THE CRAJSTIAL OSTEOLOGY, 



Mandible much deflected, with bluntly rounded symphysis, width of which is at least 



three quarters of, and is usually more than, length of basis cranii. 

 Length of mandible more than four times that of basis cranii. 



Genus Dinornis. 



Occipital plane inclined forwards, condyle projecting beyond middle of supra- 



foraminal ridge ; occipital crest usually indistinct. 

 Paroccipital process short, and evenly rounded below; projects beyond occipital 



condyle. 

 Width of cranium at squamosals from two and a third to two and a half times length 



of basis cranii. 

 Mamillar tuberosities very large and prominent ; a large precondylar fossa. 

 Margin of tympanic cavity forms a continuous curve. 

 Temporal fossa large ; distance between temporal ridges about two thirds of width 



of cranium at temporal fossae ; width of temporal fossa more than half length of 



basis cranii : no mid-temporal ridge. 

 Temporal and lambdoidal ridges usually distinct, but occasionally in contact. 

 Posterior tympanic fossa wide ; inferior temporal ridge prominent, usually stops 



short of pretympanic process. 

 Zygomatic process very short. 



Postorbital process angled, consisting of horizontal and descending portions. 

 Antorbital strong, deeply excavated above by a large supraorbital fenestra ; its ventral 



edge forms a strong transverse postchoanal bar. 

 Prenarial septum very distinct. 

 Maxillo-jugal arch compressed, gently curved. 

 Quadrate has a rather long and compressed orbital process ; pneumatic foramen of 



variable size, but usually very large, on mesial surface of otic process ; occasionally 



two additional foramina on posterior surface. 

 Posterior angular process of mandible small or obsolete. 



Subfamily Anomaloptertgin^. 



Width of cranium at paroccipital processes less than twice length of basis cranii. 

 Distance between optic foramina usually less than one third and never much more 



than one half length of basis cranii. 

 Orbit evenly curved, sinuous, or obtuse-angled (right-angled in Meso])teryx, 



species y). 

 Greatest length of prem axilla less than two and a half times that of basis cranii. 



