CLASSiriCATION, AND PHTLOGENT OF THE DINOENITHID^. 409 



Vomer more than double length of basis cranii ; flattened in front, trough-like and 

 forked behind ; articulates with maxillo-palatines ; connected with palatines by 

 ligament. 



Palatine slender ; expanded posteriorly and ankylosed to pterygoid ; about two and 

 a half times length of basis cranii. 



Mandible weak ; symphysis flat, with very obscure median ventral ridge. 



Rhea. 



Occipital plane inclined backwards ; occipital condyle sessile ; occipital crest 



obscure. 

 Length of cranial roof nearly three times that of basis cranii. 

 Width at paroccipital processes about one and a half times length of basis cranii. 

 Width at squamosals less than double length of basis cranii. 

 Height of cranium about one and a half times length of basis cranii. 

 Temporal fossae continued on to parietal region ; distance between temporal ridges 



about one third less than width of cranium at temporal fossae. 

 Zygomatic process slender, outstanding ; no squamosal prominence. 

 Width of orbit about equal to width of cranium at paroccipital processes, or one and 



a half times length of basis cranii; interorbital septum present; supraorbital 



ledge narrow, not notched in front, produced behind into short blunt post- 

 orbital processes. 

 Lacrymal produced into pointed, backwardly-dixected orbital process and curved 



descending process which passes mesiad of lacrymal duct. 

 No maxillary process to nasal ; mesethmoid appears on dorsal surface between 



posterior ends of nasals. 

 Antorbital quite unossified in the skulls examined. 

 Premaxilla weak ; body flat, with no prenarial septum ; long palatine processes ; 



width of body rather less than length of basis cranii. 

 Maxilla broad; anterior end does not reach to body of premaxilla ; maxillo-palatine 



a broad, thin plate, perforated by small and variable apertures, and produced 



dorsad into a narrow vertical plate, at the base of which is a vestige of the 



antrum. 

 Vomer about double length of basis cranii ; flattened and deeply forked in front, 



carinate and deeply forked behind ; not ankylosed to palatines. 

 Palatine a broad, thin, curved plate, not ankylosed to pterygoid, and shorter than 



basis cranii. 

 Mandible weak; symphysis flat, with a median ventral ridge. 



