920 BIRDS — ALCIDAE. 



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

 with parallel transverse grooves. Ceroma tumid, thickened. 



Oeratohlepharum, 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, i^. arctica, cornicidata. 

 Gymndblepharum, Brandt. — No horny appendage to the upper eyelid. Grooves 

 of hill arched forwards. An elongated tuft of feathers occupying the place of 

 the groove in the preceding suh-genus. Species, F. cirrhata. 



