920 
BIRDS — ALCIDAE. 
10. Fratercula, Briss. — Bill very high, much compressed, lateral outline oval ; the tip 
with parallel transverse grooves. Ceroma tumid, thickened. 
Geratoblepharum, Brandt. — A horny triangular appendage above the upper eyelid. 
Grooves at tip of bill arched backwards. An elongated furrow in the plumage 
from the eyes to the nape. Species, F. arctica, cormculata. 
Gymnoblepliarum, Brandt. — No horny appendage to the upper eyelid. Grooves 
of bill arched forwards. An elongated tuft of feathers occupying the place of 
the groove in the preceding sub-genus. Species, F. cirrhata. 
