37a ARCTIC TERN. 



ly arched, the ridge rather broad and convex at the base, narrow towards 

 the end, the sides convex, the edges sharp and inflected, the tip acute. 

 Nasal groove extended beyond the nostrils nearly to the tip ; nostrils ba- 

 sal, hnear, direct, pervious. Lower mandible with the angle extremely 

 narrow, very acute, extending beyond the middle, the dorsal line straight, 

 the sides erect and slightly convex, the sharp edges inflected, the tip ex- 

 tremely acute. 



Head of moderate size, oblong ; neck of moderate length ; body very 

 slender. Feet very small; tibia bare for a considerable space ; tarsus ex- 

 tremely short, slender, roundish, covered anteriorly 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 se- 

 cond much shorter, all scutellate above, the anterior connected by reti- 

 culated 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 vermiHon 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 grey- 

 ish-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 15^ inches, to end of wings 13|, to end of claws 

 9| ; extent of wings 32 ; wing from flexure lOJ ; tail to end of shortest 

 feathers 3;^, to end of longest 7^ ; bill along the ridge 1^, along the edge 

 of lower mandible m ; tarsus i^^ ; middle toe «|, its claw f|. Weight 

 2f oz. 



