106 TRUDEAU'S TERN. 



anterior part to the edge of the mandible about three-fourths of an inch 

 from the tip. Lower mandible with the angle long, very narrow, and 

 pointed, the outline of the crura a little concave, that of the rest ascending 

 and straight, a very slight prominence or angle being formed at their junc- 

 tion, the sides erect and slightly convex, the edges sharp and inclinate, the 

 tip acuminate, the gap-line slightly arcuate. 



Head of moderate size, ovato-oblong, neck of moderate length; body 

 slender. Feet small; tibia bare for half an inch; tarsus very short, com- 

 pressed, 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 

 towards the end, 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 moderate length, deeply forked, 

 of twelve feathers, of which the middle are rounded, and three inches shorter 

 than the outer, which taper to a slender point. 



Bill black, with part of the base of the lower mandible, the edges of both 

 mandibles, and their tips to the length of five-twelfths of an inch, yellow. 

 Iris brown. Feet orange-yellow; claws dusky-yellow. Surrounding the 

 eye, and extending toward the nape, is a band of blackish-grey; the fore part 

 of the head, the lower e}^elid, the cheeks, and the upper part of the throat, 

 are white. The rest of the upper and lower parts are light greyish-blue, 

 excepting the axillar feathers, the lower wing-coverts, and the rump, which 

 are white; the tail-coverts and tail are greyish-white. The primary coverts 

 and quills are hoary, but the outer five are dusky-grey on the inner web, 

 toward the margin, and less so along the shaft, and on the outer web; but 

 the shafts of all the quills and tail-feathers are white, as are the inner edges 

 of the primaries and the tips of the secondaries, the inner excepted. 



Length to end of tail 16 inches; to end of wings 15; bill along the ridge 

 1 T 8 2, along the edge of lower mandible 2^; wing from flexure 10}§; tail to 

 end of middle feather 2 T %, to end of lateral feather 5 T 8 2 -; tarsus 1 T %; hind 

 toe T 3 2, its claw -£f ; middle toe ||, its claw ff . 



This species has the bill more slender than Havell's Tern, and differently 

 coloured, the tarsus shorter, and the lower parts of the body and neck of 

 the same tint as the upper, whereas that species is white beneath. 



It is probable that both species have the upper part of the head and the 

 nape black in summer. 



