514 RISSA. 



Head rather large, ovato-oLlong, anteriorly eompressed. 

 Eyes rather small ; eyelids feathered, -svith hare cremilati- 

 margins. Aperture of ear of moderate size, roundish. ^Neck 

 stout and of moderate length ; body moderately full. Legs 

 very short; tibia bare to a moderate extent; tarsus very 

 short, considerably compressed, covered anteriorly Avith 

 decurved sciitella, laterally and behind Avith small, nearly 

 flat scales. Hind toe extremely diminutive, Avith a mintite 

 claw, obsolete in old individuals ; fore toes of moderate 

 lencth, the shortest as long as the tarsus, the outer little 

 shorter than the third, all with numerous scutella, flattened 

 beneath, the lateral moderately margined. Claws rather 

 small, compressed, broadly grooved on the sides, moderately 

 arched, rather acute, that of the middle toe with the inner 

 margin expanded. Interdigital membranes slightly emargi- 

 nate, continuous. 



Plumage full, close, elastic, soft, and blended ; on the 

 back and wings somewhat compact. Wings very long, rather 

 narrow, pointed, with twenty-eight quills ; primaries rather 

 narrow, tapering to an obtuse point ; secondaries narrowly 

 rounded, the outer incurvate. Tail of moderate length, even, 

 of twelve abruptly-rounded feathers, of moderate breadth. 



The only species known is dispersed in summer over the 

 arctic and colder temperate regions, and advances southward 

 in winter into the warmer temperate climates. It lives on 

 small fishes, Crustacea, and moUusca, and is less suspicious of 

 danger from man than most species of this family. This 

 genus exhibits some affinity to the Procellarise. In its own 

 group it seems to intervene between Cetosparactes and Larus. 

 As in the first of these genera, the young are spotted with 

 black, but only on the back and wings. 



