270 
THE ARCTIC TERN. 
extremely short, slender, roundish, covered anterioi'ly with small scutella, 
laterally and behind with reticular scales ; toes very small, slender, the first 
extremely small, the third longest, the fourth nearly as long, the second 
much shorter, all scutellate above, the anterior connected by reticulated webs 
having a concave margin ; claws arched, compressed, acute, that of hind toe 
smallest, of middle toe by much the largest, and having the inner edge thin 
and dilated. 
Plumage soft, close, blended, very short on the fore part of the head ; the 
feathers in general broad and rounded. Wings very long, narrow, and 
pointed ; primary quills tapering, slightly curved inwards, the first longest, 
the rest rapidly graduated ; secondary short, broad, incurved, rounded, the 
inner more tapering. Tail long, very deeply forked, of twelve feathers, of 
which the outer are tapering, the middle short and rounded. 
Bill, mouth, and feet, vermilion tinged with carmine. Iris brown. The 
upper part of the head and elongated occipital feathers greenish-black ; the 
sides of the head and chin white ; the upper parts pale greyish-blue, the rump 
lighter, the tail white, excepting the outer webs of the two lateral feathers 
which are dusky-grey ; primaries dusky towards the ends, the two outer with 
their outer webs blackish, all with the greater part of the inner web white ; 
secondaries tipped with white. Neck, breast, and sides pale greyish-blue, 
like the upper parts, but lighter ; abdomen, under tail-coverts, and lower 
surfaces of wings and tail white. 
Length to end of tail 151 inches, to end of wings 132, to end of claws 
91 ; extent of wings 32 ; wing from flexure 10i ; tail to end of shortest 
feathers 3i, to end of longest 7h ; bill along the ridge 1£, along the edge of 
lower mandible l}f ; tarsus ; middle toe f-i, its claw \ i . Weight 21 oz. 
