LESSER BLACK-BACKED GULL. 539 



two-tliirds, then declinato-deciirvate, the ridge convex, the 

 sides sloping- and convex, until near the tip, when they are 

 flattened and erect, the edges sharp, the tip narrow and sharp- 

 edged ; the lower mandible with the angle long and very 

 narrow, the outline of the crura concave, and descending to 

 the angle, where an obtuse prominence is formed, the dorsal 

 line ascending and concave, the sides convex at the base, 

 sloping outwards, and flattened towards the end, the edges 

 sharp, toward the end decurved, the tip narrow, but obtuse. 



The nostrils are linear-oblong, wider anteriorly, four- 

 tAvelfths of an inch long, pervious, a little nearer the edge, 

 than the ridge. The eyes are rather small, their aperture 

 three- twelfths and a half. That of the ear roundish, and 

 rather small. The, feet are rather short and slender; the 

 bare part of the tibia slender, and with very small roundish 

 scales ; the joint large and similarly covered ; the tarsus com- 

 pressed, anteriorly with eighteen scutella, which are narrow, 

 transversely elongated, and arcuate ; the hind part with 

 several longitudinal series of small roundish subangular scales. 

 The first toe is exceedingly small, with only one scutellum; the 

 second with nineteen, the third with thirty-tAvo, the fourth 

 with twenty-two ; the claws are small, curved, strong ; that 

 of the middle toe much larger, curved outwards, with a dilated 

 thin inner edge. 



The plumage is full, elastic, soft, excepting on the back 

 and wings blended ; the featliers much curved, broad, and 

 rounded. The wings are very long, rather narrow, and 

 pointed ; the quills thirty-tAvo ; the primaries tapering to a 

 rounded point ; the first longest, the rest rapidly decreasing ; 

 the secondaries incurved and truncato-rotundate, excepting 

 the inner. The tail is of moderate length, nearly even, the 

 lateral feathers four-twelfths shorter. 



The bill is rich yellow, Avith an orange-red patch on the 

 lower mandible, the edges at the base pale v-ermilion, as are 

 the margins of the eyelids. The iris pale or straw yellow, 

 the sclerotic purplish-grey. The feet are rich gamboge-yellow, 

 becoming ])aler upwards ; the claws black. The plumage, 

 with exception of the back and wings, is snow-white, but the 

 head and neck are longitudinally streaked with pale brown. 



