LABin^: GULLS, TEENS, ETC. 733 



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 Scohpacidce, and can hardly 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 aU the tracts stiU broader and stronger than in " the gulls ; while in the petrels, 

 "the tract formation of the jagers 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. SuBOEDEE 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 Bissa, better developed than in the petrels. The habitat is fluviatile, 

 lacustrine and maritime, 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. No 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 moderate length, 

 straight, rather stift'. Legs placed well forward on the abdomen, more or less perfectly ambu- 

 latorial. Thighs entirely covered and concealed. Tibise projecting ; feathered above ; a con- 

 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 

 scuteUate, posteriorly and laterally reticulate. Anterior toes of moderate length, the middle 

 usually about equal to the tarsus ; the outer shorter than the middle, intermediate between it 

 and the inner j scuteUate superiorly; all of normal number of segments (3, i, 5). Hallux 

 present ; very small, short, elevated above the plane of the other toes ; entirely free and dis- 

 connected ; of the normal number of segments (2) — except in Bissa. Webs broad and full, 

 extending to the claws ; their sui-faces finely reticulated, their edges usually more or less incised, 

 sometimes rounded. Claws fully developed, compressed, cui-ved, 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 



