920 BIRDS — ALCIDAE. 



10. Fratercula, Briss. — Bill very high, much compressed, lateral outline oval ; the tip 

 with parallel transverse grooves. Ceroma tumid, thickened. 



Geralohlepharum, Brandt. — A horny triangular appendage above the upper eyelid. 

 Grooves at tip of hill arched backwards. An elongated furrow in the plumage 

 from the eyes to the nape. Species, F. arctica, corniculata. 

 Gymnoblepharum, 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. 



