CLASSIFICATION, AND PHYLOGBNT OP THE DINOENITHID^. 413 



Zygomatic process short, pointed, and nearly parallel to median plane ; auditory 

 region of skull produced into a strong squamosal prominence. 



Width of orbit about half width of cranium at paroccipital processes, and almost 

 invariably less than length of basis cranii ; interorbital septum absent or greatly 

 reduced ; a broad supraorbital ledge, produced behind into a strong, broad, post- 

 orbital process. 



Lacrymal ankylosed with frontal, forming a preorbital process ; no orbital process ; 

 a descending process ankylosed with outer border of antorbital and notched or 

 perforated for lacrymal duct. 



Mesethmoid produced into paired horizontal triangular processes. 



Antorbital well ossified ; ankylosed to descending process of lacrymal ; perforated 

 dorsally by a supraorbital fenestra of variable size. 



Nasal either has a slender maxillary process, or there is a distinct maxillo-nasal bone ; 

 meets its fellow of the opposite side in the middle line above the ethmoid, so that 

 the latter does not appear on the dorsal surface ; premaxillary groove on upper 

 surface of nasals extends backwards to or beyond naso-frontal suture. 



Premaxilla strong ; body more or less elevated, and with a distinct prenarial septum ; 

 palatine processes broad and produced into more or less definite vomerine processes ; 

 width of body always more than half and sometimes one and a half times length of 

 basis cranii. 



Maxilla short and narrow ; maxillo-palatine a short, flat plate, produced dorsad either 

 into an irregular shell of bone containing a large antrum, or into a thick, obhque 

 plate, containing no, or but little, trace of the antrum. 



Vomer less than one and a half times length of basis cranii ; consists of thin paired 

 plates meeting each other ventrad in an acute dihedral angle, and either quite 

 free or partially ankylosed with one another in front ; firmly ankylosed behind, in 

 fully adult specimens, with palatines and pterygoids. 



Palatine a thin twisted plate, about one and a fifth times length of basis cranii ; 

 pedate posterior end produced into short mesial vomerine process ; articulates at 

 anterior end with maxilla, and posteriorly with vomer and pterygoid, with which, 

 in fully adult specimens, it becomes ankylosed. 



Mandible very strong ; symphysis short, more or less flattened and ridged below ; 

 distal end more or less deflected downwards. 



7. The Classification op the DiNOKNiTHiD.dE. 



At an early period of his investigations— in 1846 — Owen was led to the conclusion that 

 the differences between certain of the Moas were of more than specific value, and 

 instituted the genus Palapteryx for the reception of species {ingens and dromioides) in 

 which the hallux was present. Further investigations, however, convinced him that 

 the retention of a purely vestigial structure was not, even if constant, of sufficient 



VOL. xrii. — PART XI. No. 6. — October, 189^}. 3n 



