410 PEOF. T. JEFFEEY PAEKEE ON THE CEANIAL OiSTEOLOGY, 



Drom^us. 



Occipital plane inclined backwards ; occipital condyle sessile ; occipital crest obscure. 



Length of cranial roof less than three times length of basis cranii. 



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



Width at squamosals nearly twice length of basis cranii. 



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



Temporal fossa nearly vertical ; distance between temporal ridges equal to width of 



craniiim at temporal fossae. 

 Zygomatic process strong and outstanding ; bears facet for quadrate on the inner 



surface of its distal end ; no squamosal prominence. 

 Width of orbit rather greater than width of cranium at paroccipital processes, and 



about one and a half times length of basis cranii ; interorbital septum present ; 



supraorbital ledge narrow, not notched in front, produced behind into a short 



postorbital process. 

 Lacrymal produced into a pointed, backwardly-directed orbital process, and a slender 



descending process, which is perforated for the lacrymal duct. 

 Antorbital well ossified and ankylosed laterad with the descending process of the 



lacrymal ; a deep Harderian fossa. 

 Maxillary process of nasal vestigial ; mesethmoid appears dorsally between posterior 



ends of nasals. 

 Premaxilla weak ; body flat, with a very short prenarial septum ; palatine processes 



long, width of body rather less than length of basis cranii. 

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



palatine thin and pocket-like, containing a wide antrum. 

 Vomer nearly two and a half times length of basis cranii ; broad, flat, and longitu- 

 dinally grooved in front, narrow and deeply forked behind ; ankylosed to ptery- 

 goids. 

 Palatine a thin, oblique plate, somewhat longer than basis cranii, articulating in 



front with maxilla and behind with pterygoid. 

 Mandible weak ; symphysis flat with a narrow ventral ridge. 



Casitarius. 



Occipital plane inclined backwards ; occipital condyle sessile ; occipital crest 



obscure. 

 Cranial roof produced into a large crest ; nearly three times length of basis cranii. 

 Width at paroccipital processes nearly double length of basis cranii. 

 AVidth at squamosals double length of basis cranii. 

 Height of cranium, not counting crest, nearly double length of basis cranii. 



