HAVELL'S TERN. 123 



ing to beyond the middle, the outline of the crura a little concave, that 

 of the rest ascending and straight, a slight prominence or angle being 

 formed at their junction, as in Gulls, the sides erect and slightly convex, 

 the edges sharp and incliaate, the tip acuminate, the gape-line slightly 

 arcuate, 



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

 der. Feet small ; tibia bare for seven-twelfths of an inch ; tarsus very 

 short, compressed, anteriorly scutellate ; toes small, slender ; the first 

 extremely small, the third longest, the fourth much longer than the 

 second ; all scutellate above, the anterior connected by reticulate webs, 

 of which the inner is more deeply emarginate. Claws moderately 

 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 tapering 

 to an obtuse point ; the first longest, the second half an inch shorter, the 

 rest rapidly graduated ; secondaries short, incurved, obliquely pointed, 

 some of the inner proportionally longer and narrower. Tail of mode- 

 rate length, deeply forked, of twelve feathers, of which the middle are 

 rounded, and three inches and a quarter shorter than the outer, which 

 taper to a slender point. 



Bill black, with the base of the lower mandible tinged with brown, 

 and a very small portion of the tip yellowish. Iris brown. Feet 

 orange-yellow ; claws dusky. Surrounding the eye, and extending to- 

 ward the nape, is a broad band of black ; the fore part of the head, 

 the lower eyelid, and all the under parts are pure white ; the hind part 

 of the head and the nape are dusky grey, mixed with white. The rest 

 of the upper parts are light greyish-blue, excepting the rump which is 

 white, the primary coverts and quills as well as the tail-feathers and 

 their coverts, are hoary, with the shafts white ; but five of the quills 

 are dusky on the outer web, on the inner along the shaft, and on the 

 inner margin toward the end. 



Length to end of tail 15J inches ; bill along the ridge lj\, along 

 the edge of lower mandible 2i% ; wing from flexure lOi*^ ; tail to end 

 of middle feather 2i^g, to end of longest feather 6^^; tarsus "|, hind 

 toe /j, its claw ^^ ; middle toe ig, its claw ^|. 



This species differs from the Marsh Tern, Sterna anglica, in being 



