THE GREAT BLACK-BACKED GULL. 
65 
Adult Male in summer. 
Bill shorter, than the head, robust, compressed, higher near the end than 
at the base. Upper mandible with the dorsal line nearly straight at the base, 
declinate and arched towards the end, the ridge convex, the sides slightly 
convex, the edges sharp, inflected, arcuate-declinate towards the end, the tip 
rather obtuse. Nasal groove rather long and narrow ; nostril in its fore 
part, lateral, longitudinal, linear, wider anteriorly, pervious. Lower mandi- 
ble with the angle long and narrow, the outline of the crura rather concave, 
as is that of the remaining part of the mandible, a prominent angle being- 
formed at their meeting, the sides nearly flat, the edges sharp and inflected. 
Head rather large, oblong, narrowed anteriorly. Neck of moderate 
length, strong. Body full. Wings long. Feet of moderate length, rather 
slender ; tibia bare below ; tarsus somewhat compressed, covered anteriorly 
with numerous scutella, laterally with angular scales, behind with numerous 
small oblong scales, hind toe very small and elevated, the fore toes of 
moderate length, rather slender, the fourth longer than the second, the third 
longest, all scutellate above, and connected by reticulated entire membranes) 
the lateral toes margined externally with a narrow membrane. Claws 
small, slightly arched, depressed, rounded, that of middle toe with an 
expanded inner margin. 
The plumage in general is close, full, elastic, very soft and blended, on 
the back rather compact. Wings very long, broad, acute, the first quill 
longest, the second scarcely shorter, the rest of the primaries rather rapidly 
graduated ; secondaries broad and rounded, the inner narrower. Tail of 
moderate length, even, of twelve rounded feathers. 
Bill gamboge-yellow, the lower mandible bright carmine towards the end. 
Edges of eyelids bright carmine, iris, silvery. Feet yellow, claws black. 
The head, neck, and all the lower parts, pure white ; back and wings deep 
blackish-grey tinged with purple, or dark slate-colour ; the rump ancf tail 
white, as are the edges of the wing, and a large portion of the extremities 
of all the quills ; the second, third, fourth, and fifth primaries have a broad 
band of black across their ends, the inner web only of the second being so 
marked, in some specimens however both webs. The oesophagus is very 
large, the gizzard small, the intestine four feet long, and about the thick- 
ness of a goose quill. 
Length to end of tail 29f inches, to end of wings 31i, to end of claws 
29£ ; extent of wings 67 ; wing from flexure 20 ; tail 9 ; bill along the ridge 
2f°, along the edge of lower manible 3 j® 2 ; its depth at the angle 1, at the 
base ; tarsus 3 T 2 2 ; middle toe 2£, its claw i. Weight 3 lbs. 
The Female is similar to the male, but considerably less. 
The Young, when fledged, have the bill brownish-black, the iris dark 
Vol. VIII.— -9 
