2. Otus. One or two outer quills with their inner webs emarginated. With or without ear-tufts. Bill blackish; iris yellow. Size medium.
Ear-tufts well developed; only one quill emarginated … Otus.
Ear-tufts rudimentary; two quills emarginated … Brachyotus.
b. Cere, on top, less than the chord of the culmen; gradually ascending basally, or level (not arched). Ear-conch nearly the height of the skull, with the operculum extending only a part of its full length, or wanting entirely.
† Anterior edge of the ear-conch with an operculum; the two ears asymmetrical.
3. Syrnium. Five to six outer quills with their inner webs emarginated. Top of cere more than half the culmen. Without ear-tufts. Bill yellow; iris yellow or black. Size medium or large.
Six quills emarginated; toes densely feathered, the terminal scutellæ concealed; iris yellow. Size very large … Scotiaptex.
Five quills emarginated; toes scantly feathered, the terminal scutellæ exposed; iris black. Size medium … Syrnium.
4. Nyctale. Two outer quills with inner webs emarginated. Top of cere less than half the culmen, level. Without ear-tufts. Bill yellow or blackish; iris yellow. Size small.