422 Synopsis of the Birds 



a slight rudimental furrow, sub-basal, lateral, concave, lon- 

 gitudinal, linear, pervious, covered partially by the feathers 

 of the front advancing far on the bill : tongue moderate, 

 linear, acute, entire. Head oblong, depressed, narrowed be- 

 fore, rounded posteriorly ; eyes small : neck short, moderately 

 robust : body stout, elongated. Feet placed very far back ; 

 lower extremity only of the tibia apparent ; tarsus one-fourth 

 shorter than the middle toe, slender, compressed, carinated 

 anteriorly : middle toe longest; inner by one third shortest, 

 subequal to the tarsus ; webs not very broad : nails compres- 

 sed, moderately curved, acute ; middle one larger, dilated 

 internally into a sharp edge. Wings short, narrow, acute ; 

 first primary longest. Tail very short, rounded, of twelve 

 feathers. 



Female smaller, similar to the male. Young differing from 

 the adult, but almost similar to their winter dress. Moult 

 twice a year, changing the colors of their plumage. Colors 

 black and white. 



Keep always near the sea, leaving it only when breeding, not 

 found on fresh water except when straying inland. Walk with 

 difficulty, and only when obliged to cross the ice, in an < rect 

 posture. Flight short, though rapid, just skimming the sur- 

 face of the water: reaching the top of high rocks by jump- 

 ing and fluttering from point to point. Swim and dive ad- 

 mirably, even beneath the ice, driving their submarine prey 

 by employing their wings as fins, appearing to fly under 

 water. Feed principally on fishes. Breed socially in the 

 clefts of perpendicular rocks: lay without the least preparation 

 on the naked rock, one or two eggs at most, disproportion- 

 ately large, and with a very hard shell : feed their young 

 with fishes, which they carry to them in their bill. Eggs, 

 feathers, and flesh of the young, sought after. 



Inhabit the Arctic seas, -whence they migrate in summer to 

 the temperate coasts all round the globe. Our five species 

 are the only well ascertained of the genus. 



