412 PKOF. T. JEFFEET PAEKEE OK THE CEANIAL OSTEOLOGY, 



Zygomatic process directed forwards and strongly compressed ; no squamosal 



prominence. 

 Orbit small and ill-defined; no interorbital septum, supraorbital ledge, or post- 

 orbital process. 

 Lacrymal ankylosed to aliethmoid and perforated for lacrymal duct ; no orbital 



process. 

 Antorbital not clearly marked off from rest of aliethmoid, which is strongly convex, 



completely ossified, and extends backwards to the optic foramen. 

 Nasal has maxillary process ankylosed to lacrymal ; mesethmoid appears dorsally 



between posterior ends of nasals, but complete ankylosis of the bones in this 



region takes place in the adult. 

 Premaxilla strong and greatly elongated; body short but high, with a very short 



prenarial septum ; narrow palatine processes ; width of body not more than one- 

 fifth length of basis cranii. 

 Maxilla broad and flat ; articulates in front with maxillary and palatine processes of 



premaxilla; maxillo-paiatine represented by the thin mesial border of the bone; 



no bony antrum. 

 Vomer about twice length of basis cranii ; flattened and narrow in front ; broad, 



keeled, and deeply clelt behind ; ankylosed to palatines and pterygoids. 

 Palatine a thin, twisted plate with pedate posterior end ; about one and three 



quarters length of basis cranii ; ankylosed in front and by its entire outer border 



to maxilla and behind to vomer and pterygoid. 

 Mandible strong ; symphysis occupies more than half its length, narrow, strongly 



keeled below. 



DlNORNITHID^. 



Occipital plane vertical or very slightly inclined backwards or forwards ; occipital 



condyle pedunculate ; occipital crest variable. 

 Length of cranial roof from two to two and a half times length of basis cranii. 

 Mamillar tuberosities usually prominent ; basitemporal platform always well defined 



and separated from occipital condyle by a deep precondylar fossa. 

 Width at paroccipital processes from less than one and a half to more than twice 



length of basis cranii. 

 Width at squamosals from about one and three quarters to two and a half times 



length of basis cranii. 

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

 Temporal fossa extends mesiad to a greater or less extent on to parietal region ; 



distance between temporal ridges varies from about width of cranium at temporal 



fossae to half that width. 



