570 STRUCTURAL CHARACTERS 



3. FAMILY CAPRIMULGID-ffi. 



Beak extremely short, wide at the gape, which extends below the eye ; rictal bristles very long, 

 (a) Genus Caprimulgus. Feet partly syndactyle ; tarsus partly feathered ; tail long 

 and truncated. (Vol. ii. p. 362.) 



SUBORDER: STRIGES OWLS 



Beak raptorial, and with a more or less conspicuous cere ; feathers of face forming a disc ; 

 hallux reversible ; foot of the raptorial type ; wing diastataxic ; desmognathous palate ; caeca 

 large ; basipterygoid processes well developed. 



4. FAMILY STRIGID.E. 



The median branch of the ventral feather-tract joining the inner branch posteriorly ; the 

 feathers of the acrotarsiuin directed upwards ; oil-gland with two or three filoplumous 

 feathers at its tip ; orbit small ; interorbital septum extremely thick ; palatines fused 

 behind the vomer. 



(a) Genus Strix. External aperture of ear quadrangular, its vertical axis half the 

 horizontal axis of the eyelid ; covered with small quadrangular operculum. 

 (Vol. ii. p. 379.) 



5. FAMILY ASIONIDjE. 



The median branch of the ventral feather- tract free posteriorly ; feathers of the planta 

 directed downwards ; no filoplumes on the oil-gland. 



(a) Genus Asio. Height of the vertical axis of the external aperture of the ear three 

 times that of the horizontal axis of the eyelid ; operculum of great size, provided 

 with a valve ; post-aural fold voluminous ; apertures asymmetrical ; oil-gland 

 napiform. (Vol. ii. p. 384.) 



(6) Genus Bubo. 1 Height of the vertical axis of the external aperture of the ear not 

 exceeding that of the horizontal axis of the eyelid ; without an operculum ; 

 symmetrical oil-gland conical. (Vol. iv. p. 504.) 



(c) Genus Scops. Posterior division of the cavernuin extending its whole vertical 



height ; cere laterally inflated. (Vol. iv. p. 503.) 



(d) Genus Syrnium. Posterior division of the cavernum confined to the lower third ; 

 peripheral disc-feathers meeting in the middle line near the symphysis of the 

 mandible ; inner branch of the ventral tract arising over the region of the head of 

 the coracoid. (Vol. ii. p. 381.) 



(e) Genus sEgolius (Nyctala). Interscapular region of the dorsal feather-tract with 



a short bifurcation ; vertical axis of the external ear twice that of the horizontal 



axis of the eyelid ; covered by an operculum. (Vol. iv. p. 502.) 

 (/) Genus Surnia. Vertical axis of the ear equal to that of the horizontal axis of the 



eyelid; no operculum; tail long and pointed; oil-gland napiform. (Vol. iv. p. 503.) 

 (g) Genus Athene. Vertical axis of the external ear half that of the horizontal axis 



of the eyelid ; operculum wanting ; cere short, much inflated, forming two pisiform 



swellings on either side of the culmen. (Vol. ii. p. 389.) 



SUBORDER: CORACLE 



With syndactyle foot, a long spina externa and no spina interna, or with the front toes free 

 and a spina communis ; an aftershaft ; a desmognathous palate and functional creca. 



1 The genus Nyctea (vol. ii. p. 391), save in the matter of colour and the shorter ear-tufts, is indistinguishable 

 from that of Bubo. 



