LARID^: GULLS, TERNS, ETC. 
783 
little muscular ; the coeca are variable ; the cloaca. is large. Certain genera offer peculiarities 
of this general type of alimentary canal. According to Nitzsch, the pterylosis of the gulls 
''approaches very closely that of the Scolopacidce, and can liardly be distinguished therefrom 
with certainty by any character." In the terns, "in consequence of the slender and elegant 
form of the body, the tracts are very narrow, and perfectly scolopacine." The jagers differ 
"in having the outer branch of the inferior tract united with the main stem in the first part of 
its course, and all the tracts still broader and stronger than in " the gulls ; while in the petrels, 
''the tract formation of the jiigers is elevated into the type of a group, undergoing scarcely 
any change in the form of the inferior tract, but showing some little modification of the dorsal 
tract." 
As here constituted, the order embraces two superfamilies or suborders, to be known by 
the character of the nostrils ; both are well represented in this country, where occur all the 
leading genera excepting Halodroma. 
19. Suborder GAVI.^ : Slit-nosed Longwings. 
The character of this group is the same as that of its single 
59. Family LARID^. Gulls, Terns, etc. 
Nostrils not tubular (linear, linear-oblong, oval or drop-shaped), sub-basal or median, 
lateral, pervious. The hallux, though very small and elevated, with its tip hardly touching 
the ground, is, except in Rissa, better developed than in the petrels. The habitat is fiuviatile, 
lacustrine and matitime, rather than pelagic. The family contains four leading genera, each 
of which may be assumed as the basis of a subfamily ; all four occur in North America. Fuller 
characters are : Bill of moderate length, entire, or furnished with a cere, the upper mandible 
longer than, as long as, or shorter than the under; the culmen convex; the commissure very 
large, the cutting edges without lamellae, the symphysis of the inferior mandibular rami com- 
plete for a considerable distance, an eminence being formed at their junction. Ko gular sac. 
Feathers usually extending farther on the sides of the upper mandible than on the culmen, and 
farther between the rami than on the sides of the under mandible. Nostrils, linear or oval ; 
direct, pervious, lateral, opening on the basal half of the bill. Eyes of moderate size, placed 
about over the angle of the mouth. Wings long, broad, strong, pointed, With little or no con- 
cavity. Primaries very long, more or less acute, the first longest, the rest rapidly graduated. 
Secondaries numerous, short, broad, with rounded or excised tips. Tertials of modei-ate length, 
straight, rather stift'. Legs placed well forward on the abdomen, more or less perfectly ambu- 
latorial. Thighs entirely covered and concealed. Tibiae projecting ; feathered above ; a ct)n- 
siderable portion below naked, covered with more or less dense, sometimes reticulated, skin. 
Tarsi of moderate length or rather short ; compressed ; rather slender ; anteriorly transversely 
scutellate, posteriorly and laterally reticulate. Anterior toes of moderate length, the middle 
usually about equal to the tarsus ; the outer shorter than the niiddle, intermediate between it 
and the inner; scutellate superiorly; all of normal number of segments (3, 4, 5). Hallux 
present ; very small, short, elevated above the plane of th<! other toes ; entirely free and dis- 
connected ; of the normal number of segments (3) — except in Rissa. Webs broad and full, 
extending to the claws ; their surfaces finely reticulated, their edges usually more or less incised, 
sometimes rounded. Claws fully developed, compressed, curved, more or less acute, the edge 
of the middle dilated, but not serrated. Tail very variable. Body generally rather full, and 
sometimes slender. Neck rather long. Head of moderate size. Plumage soft, close, thick ; 
its colors simple — white, black, brown, or pearl-blue predominating; bright tints hardly found, 
except on the bill or feet, or as a temporary condition ; the sexes alike in color, but the plumage 
varying greatly with age and season. Eggs generally three, light -colored, with numerous 
