MARSH OR GULL-BILLED TERN. 131 



rounded at the base, narrowed toward the end ; the sides sloping at the 

 base, nearly erect and convex toward the end, the edges sharp and in- 

 flectedj the tip although narrow somewhat obtuse. Nasal groove com- 

 paratively short ; nostrils basal, oblong, direct, pervious. Lower man- 

 dible with the angle very narrow and acute, extending to beyond the 

 middle, the outline of the crura a little concave, that of the rest ascend- 

 ing and straight, a prominence or angle being formed at their junction 

 as in Gulls, the sides erect and slightly convex, the edges sharp and in- 

 clinate, the tip acute, the gape-line straight for half its length, then 

 slightly arcuato-declinate. 



Head of moderate size, ovate ; neck of moderate length ; body slen- 

 der. Feet small ; tibia bare for nearly half an inch ; tarsus very short, 

 compressed, anteriorly scutellate ; toes small, slender ; the first ex- 

 tremely small, the third longest, the fourth considerably shorter ; all 

 scutellate above, the anterior connected by reticulated webs, of which 

 the inner is more deeply emarginate. Claws a little arched, compressed, 

 very slender, that of the middle toe much larger, and having its inner 

 edge somewhat dilated. 



Plumage soft, close, blended, very short on the fore part of the 

 head. Wings very long, narrow, and pointed ; primary quills taper- 

 ing to an obtuse point ; the first longest, the second ten and a half 

 twelfths of an inch shorter, the rest rapidly graduated ; secondaries short, 

 incurved, obliquely rounded, some of the inner proportionally longer 

 and narrower. Tail of moderate length, forked, of twelve feathers, of 

 which the middle are rounded and an inch and seven-twelfths shorter 

 than the outer, which tapers to a narrow but obtuse point. 



Bill black, as are the feet. Iris brown. The upper part of the head, 

 the nape, and part of the hind neck, deep black ; sides of the head, in- 

 cluding a line margining the base of the upper mandible, fore neck, 

 and all the lower parts white ; upper parts pale greyish-blue ; the 

 edges of the wings whitish ; the primary quills hoary on the outer web, 

 deep grey on the inner, but with a large portion toward the base 

 lighter, the shafts and those of the tail-feathers white ; the tail is of a 

 paler tint than the back, and the outer feather is nearly white. 



Length to end of tail 14 inches ; extent of wings 34 ; bill along 

 the ridge l^^^g, along the edge of lower mandible 2^? ; wing from 

 flexure 12t:^j ; tail to end of middle feather S^^, to end of lateral fea- 

 ther 4^^ ; tarsus 1;^ ; first toe ^, its claw || ; middle toe {§, its 

 claw ^|. 



