MOEPHOLOGX OP THE OV^S. 39 



3. Buboninse. 



■i. Syrminse= St/ rimmi, Scotiapex, Ciccaha. 



5. liijci<\].ynvd^=^Speotyto, Gymnasio, Ni/ctala. 



6. ^\\ii:n\myd=Surnia, Athene, Glaucidium. 



I do not, however, propose to supersede the classification I originally suggested by the 

 above. It is set down here merely for the purpose of contrasting the results given by 

 the two systems. It is almost certain that the outcome of a study of the myology, 

 convolutions of the intestines, and other characters will suggest yet other combinations. 

 Obviously, therefore, it is best to Avait until a survey can be made of all the factors, before 

 really sound results can be obtained. 



XII. Key to the Families and Species. 



A. Skull. (Plates 1 and 2.) 



Upper jaw markedly hooked ; nostrils holorhinal and impervious ; with functional basipterygoid 

 processes ; lachrymal without supraorbital process and placed far forwards so as to encroach upon the 

 lachrymo-nasal fossa; lachry mo-nasal fossa greatly reduced, partly by the encroachment of the lachrymal, 

 and partly by the great upward development of the maxillo-palatiue processes ; palate with a large 

 anterior palatine vacuity ; desmognathous, the bridge being formed by ossification of the alinasal 

 cartilages forming the floor of the anterior olfactory chamber ; maxillo-palatine processes not meeting in 

 the mid-ventral line ; parasplienoidal rostrum very short. 



A. Orbit very small ; interorbital septum of great thickness ; vomer large, inflated, 



fusiform, and fused with palatines; maxillo-palatines relatively small; lachrymal 

 of great size, subconical or subquadrate, thrust far into the lachrymo-nasal fossa, 

 and leaving only a small passage for the lachrymo-nasal duct; roof of skull dome- 

 shaped, with a deep median groove, and highly pneumatic ; palatines fused one 

 with another in the middle line behind the vomer ; nasal septum deeply notched 

 along its postero-dorsal border, the notch leading into the cranio-facial fissure ; 

 floor of anterior nasal cavity perforated ; palatines fused with one another in the 

 middle line behind the vomer STRiGiDiE. 



B. Orbit moderately or very large; lachrymal columnar ; interorbital septum thin*; 



antorbital plates thin t; nasal septum without a notch posteriorly Asionid*. 



a. Orbit relatively small ; tympanic cavity large, well-defined, the " post- 

 cavernum " rising upwards to level of supraorbital process ; postorbital 

 processes small, projecting obliquely from oi'bit, and arising in front of and 

 below level of squamoso-parictal tympanic wing ; conspicuous supraorbital 

 processes; frontal between supraorbital process and base of squamoso-parictal 

 wing with strongly bevelled free edges forming a shelving supraorbital plane ; 

 nostrils very long, and with irregular inferior border ; vomer relatively largo ; 

 antorbital plate very long, nearly reaching quadrato-jugal bar ; interorbital 

 septum thick Asio. 



* Asio and Photodilus only among the Asionida) have a thick interorbital septum, but the peculiar form of the 

 tympanic cavity and of the supraorbital region render the skulls of these two genera perfectly distinguishable from 

 that of Strix. 



t In Photodilus the antorbital plate is thick, and resembles that of Strix. 



