CLASSIFICATION, AND PHYLOGENY OF THE DINOENITHID^. 417 



, These conclusions may be summarized by stating that the Dinornithidse are divisible 

 into three groups, two of highly specialized forms and one of more generalized forms, 

 which last may be again split up into three subgroups. These facts might be expressed 

 equally well by making three genera, and subdividing one of them into three sub- 

 genera, or by making three subfamilies, two of them containing a single genus apiece, 

 and the third including three genera. The latter appears to me the more convenient 

 method. Agreeing, as I do, with Hutton and Lydekker, that the differences between, 

 say, elephantopus and didiformis are of generic value, it appears to me quite clear that 

 those between rohustus and elephantopus or between didiformis and crassus are 

 something more than generic. 



Arranging the groups as nearly as possible according to their affinities as determined 

 by cranial characters, we get the following scheme : — 



Family DINORNITHID^. 



Subfamily a. Dinornithin^. 

 Genus 1. Dinoenis. 



Subfamily^. Anomalopterygin^. 



Genus 2. Pachtoenis. 

 „ 3. Mesoptertx. 

 „ 4. Anomaloptertx. 



Subfamily c. E M E i n ^e. , 

 Genus 5. Emeus. 



8. Summary op Cranial Characters of the Subfamilies and Genera 



OF THE DlNORNITHID^. 



Subfamily Dinornithin^. 



Width of cranium at paroccipital process nearly always more than twice length of 



basis cranii. 

 Distance between optic foramina about two thirds length of basis cranii. 

 Orbit right-angled. 



Greatest length of premaxilla more than two and a half times that of basis cranii. 

 Body of premaxilla deflected, bluntly rounded ; its length and width about one and 



a half times length of basis cranii. 

 Maxillo-palatine contains a large antrum. 

 Nasal has a slender maxillary process. 



