ALCID/E — TH H AUKS — FRATERCULA. 023 



extreme base ; gonys convex toward tlie l^ase, straight, or even fiometiines slightly concave, for 

 the terminal half, or more; ilecidiious nasal shield becoming rapidly narrower toward the top; 

 terminal portion of the bill transversely snlcate ; base of the maxilla snrronnded Ijy a deciduous 

 thickened horny rim, and rictus ornamented by a deciduous tumid rose.te ; eyelids furnished with 

 deciduous horny plates. No tufts about tin; head in the breeding-season. 



F. arctica. 



The deciduous accessory pieces of the bill, together with the rictal and palpebral ornaments, 

 are cast at the close of the breeding-season.^ 

 Following is a key to the known species. 



1. F. arctica. Horny process of upper eyelid short, subconical ; grooves of the l)ill very 



oblique, broad, and distinct, the deciduous shields occupying not more than the basal 

 half of the bill. Chin and whole throat grayish. 



a. arctica. Bill and general size smaller. Culmen, 1. (iO-l. 90 inches ; g(mys, 1.4(V-1.5() ; 

 depth of maxilla at base, .75-.90; of mandible, .40-.50; tarsus, 1.00-1.10 ; middle toe, 

 without claw, 1.25-1.40. Wing, 6.00-6.50. Hah. Coasts of the North Atlantic, from 

 Southern Greenland southward. 



/3. (jlacialis. Bill and general size larger. Culmen, 2.00-2.30 inches ; gonys, 1.40-1.60; 

 depth of maxilla at base, .85-1.00 ; of mandible, .70-.80 ; tarsus, 1.10-1.35 ; middle toe, 

 without claw, 1.45-1.60. Hah. Arctic Ocean, from Spitzbergen to northern and western 

 Greenland ; probably also western shores of Batiin's Bay, and Northern Labrador. 



2. F. cornlculata. Horny process of upper eyelid narrow, elongated, horn-like ; grooves of 



bill nearly vertical, narrow, and less distinct ; deciduous shields occupying much moi-e 

 than the basal half of the bill. Whole throat blackish, only the chin gray. Hah. Coasts 

 and islands of the North Pacific and Beliring's Sea. 



^ See Dr. Louis Bureau : De la Muc du Bee et des Ornements Palpobraux du XIacaroux arctiquo, 

 Fratercula arctica (Liu.), Stcph., aprfes la Saison des Amours (Bull. Soc. Zool. do France, 1S7S, pp. 1-21, 

 pis. iv. v.). 



