270 ME. \V. p. PYCEAFT ON THE 



/'. Vertical axis of the external aperture of the ear half that of the horizontal axis 



of the eyelid ; no operculum ; cavernum not divisible into anterior and posterior 



portions. 



g". Lumbar stem of pt. spinalis feebly developed or absent ; cere short, much ^ „ ^^ . 



inflated, forminff two pisiform swellings on either side of the culmen . . A ,„ ■*„ ' - 



[ 10. Speotyto. 



Key to the Species of the Family Asionidae. 



Genus 1. Asio. 



a. Lateral ucck-folds voluminous, with an oblique retractor eusheathed in a 

 prominent membranous fold. 

 a'. Upper end of the dorsal lateral neck-fold lobate ; diverticulum of the 

 cavernum broad and shallow, the membrane shutting off the via recta 



passing over a bony tubercle of the postorbital process L A. accipitrinus. 



b'. Upper end of dorsal lateral neck-fold not lobate ; diverticulum of the 



cavernum narrow and deep ; no postorbital tubercle 2. A. otus. 



Genus 2. Bubo. 



a. Vertical axis of the external aperture of the ear equal to the horizontal 



axis of the eyelid. 



a'. Interramal not connected with the ramal area ; interscapular fork 



with very long branches \. B. ignavus. 



b'. Interramal fused from gape backwards with the ramal area, which 

 extends beyond the articular region of the jaw ; interscapular fork 

 with very short branches ; lateral neck-folds with an oblique retractor 

 as in Asio 2. H. virginianus. 



c'. Interramal area contracting suddenly behind the region of the gape 

 to form a narrow band ; median and inner ventral tract sharply 

 defined ; apt. colli lateralis continued upwards on to the crown of 

 the head Z. B. maculosus. 



b. Vertical axis of the external aperture of the car less than the horizontal 



axis of the eye. 

 d'. Interramal joining the mandibular area at the gape ; interscapular 



fork with very short branches ; lateral neck-folds without a retractor. 4. B. torquatus *. 

 e'. Interramal area joined, by two separate single rows of feathers behind 

 the gape, with the ramal area ; interscapular fork with very long 

 branches ; cavernum not divisible into anterior and posterior 



portions 5. JS. lacteus. 



e. Aperture of the external ear pyriform. Interramal joined to the 

 mandibular area in front of gape by a single row of feathers, behind it 

 by a very broad baud ; interscapular fork with very long branches . . 6. B. nycteus. 



* This = the Pulsatrix iorquains (Daud.) and the Syrnmm jierspicillatum of Latham. 



