40 ME. W. P. PTCEAFT ON THE 



b. Orbit very large ; interorbital septum thick ; antorbital plate spongy ; roof of 



skull arched with supraorbital processes ; postorbital processes of great size, 

 projecting far outwards ; tympanic cavity extending upwards as a narrow gorge 

 between the postorbital and squamoso-tympanic process ( = post-cavernum) ; 

 temporal fossae wanting ; vomer vestigial Photodilus. 



c. With a small, ill-defined post-cavernum ; postorbital processes large, laterally 



projecting, and with the free edge passing into the supraorbital rim of the 



frontal, which is sharply defined. 



a'. Remains of vomer blade-shaped; palatines with mesial borders of posterior 



ends straight and meeting in middle line ; pterygoids sharply truncated, 



expanded distally and touching the parasphenoidal rostrum ; maxillo- 



palatines rising upwards so as nearly to obliterate the lachrymo-nasal fossa ; 



lachrymal small, not reaching the quadrato-jugal bar Ketupa. 



b'. Vomer vestigial ; lachrymal reaching the quadrato-jugal bar. 



a". Palatines with mesial borders of posterior ends hollowed, enclosing a 

 small space caudad of the vomer shut in by the articulation with 

 pterygoids ; with large triangular supraorbital processes ; lachrymo- 

 nasal fossa extremely reduced Pulsatrix. 



b" . Palatines with strap-shaped processes on mesial border, keeping articular 

 ends apart. 

 «'". Fronto-nasal region of interorbital roof widest ; lachrymal very large ; 



temporal fossa never bridged Bubo. 



V" . Widest portion of interorbital region of roof caudad of vestigial supra- 

 orbital processes. 

 a\ Temporal fossa frequently bridged by bar of bone from squamosal wing 



of tympanic Scops. 



b*. Quadrato-jugal with a triangular process below postorbital process. . T Ninox. 



^ Sceloglaux. 

 c'. With prominent, blunt, supraorbital processes overarching middle of orbit ; 



frontal laterally constricted behind supraorbital processes so as to cause 



postorbital processes to stand out prominently ; palatines with large 



space caudad of vomer ; vomer vestigial / yrmum. 



C Ciccaba. 

 d'. Tympanic cavity closed above by junction of squamoso-tympanic wing with 



postorbital process. 



a". Tympanic chamber symmetrical. 



a'". Temporal fossa large. 



a\ Supraorbital processes long and pointed ; nostrils nearly circular . . Speotijto. 



b*. Supraorbital processes vestigial ; nostrils oblong Gymnasio. 



b". Tympanic cavity markedly unsymmetrical ; temporal fossae vestigial . . Nyctala. 



e'. Supraorbital processes long and slender ; quadrato-jugal with a triangular 



process below postorbital process ; tympanic cavity open above ; ramal 



vacuity of mandible large. 



a". Squamosal wing of tympanic with broad, squarely truncated outer border, 



not projecting beyond postorbital process ; pterygoid long, slender, and 



straight ; tympanic cavity comparatively shallow, not rising to the level 



of the floor of the temporal fossa ; palatines wide apart caudad . . . Surnia. 



