TRUDEAU’S TERN. 
265 
anterior part to the edge of the mandible about three-fourths of an inch 
from the tip. Lower mandible with the anglb 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 eyelid, 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 S 2 , along the edge of lower mandible 2 T S 2 ; wing from flexure 10}f ; tail to 
end of middle feather 2 r ® 2 , to end of lateral feather 5 r \‘, tarsus 1^; hind 
toe 7 3 2 , its claw || ; middle toe If, its claw f- f . 
This species has the bill more slender than HavelFs 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. 
Vol. VII. — 34 
