758 SYSTEMATIC SYNOPSIS.— LONGIPENNES — GAVIA. 
Tibia bare about 0.75; tarsus 1.75, rather exceeding middle toe and claw, the scutella in 
front replaced by polygonal scales similar to but larger than those on its sides, which are 
rough ; hind toe extremely small; outer lateral nearly as long as middle toe and claw, which 
is 1.65. Bill dark vermilion red, growing lighter and somewhat ‘‘diaphanous” toward the 
tip. Pileum and occipital crest glossy greenish-black, extending to below the lower level of 
-the eyes, and occupying the termination of the feathers on the side of the mandible to the 
Fig, 512, —Caspian Tern, 3 nat. size. (From Brehm.) 
exclusion of the white; lower eyelid white, forming a noticeable spot on the greenish; a 
white streak along sides of upper mandible, not extending to the end of the feathers. Mantle 
pearl-blue, the line of demarcation between it and the white rather indefinite, both on nape 
and rump ; most of the tail-feathers, and especially the central ones, retaining a more or less 
pearly tint. Shafts of the primaries yellowish-white; primaries grayish-black, but, when 
new, so heavily silvered over as to appear of a light hoary gray, especially on their superior 
aspects. On the inner web of all there is a central light field; this is very narrow, even on 
the first primary, although it runs for some considerable distance, and on the others it rapidly 
grows less; and it has no trenchant line of division on any of the primaries from the darker 
portions of the feather. Whole inner web of secondaries pure white, outer pearl-blue. Legs 
and feet black. Adult, winter plumage: Chiefly distinguished by a diminution in the bright- 
ness of the bill, and by a change in the character of the pileum. The vermilion is replaced 
by light orange-red, growing still yellower toward the tip of the bill and along the tomia. 
