LARIDtE GULLS, ETC. 591" 



of the nostrils, beside some anatomical features. The family, thus separated from other 

 Xatatores, may be fully defined as follows : 



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 complete for a considerable distance, an eminence being formed at their junction. 

 No gular sac. Feathers usually extending further on the sides of the upper mandible 

 than on the culmen, and further between the rami than on the sides of the under 

 mandible. 



JS^ostrils linear or oval ; direct, pervious, lateral, opening on the basal half of the bill. 



Ei/es of moderate size, placed about over the angle of the mouth. 



Wings long, broad, strong, pointed, with little or no concavitj'. Primaries A^ery 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 stiff. 



Lef/s placed well forward on the abdomen, more or less perfectly ambulatorial. 

 Thighs entirely covered and concealed. 



Tibia' projecting; feathered above; a considerable 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. 



Anteror toes of moderate length, the middle usually about equal to the tarsus ; the 

 outer shorter than the middle, intermediate between it and the inner; scutellate supe- 

 riorly ; all of normal number of segments (3, 4, 5). 



Hallux present ; very small, short, elevated above the plane of the other toes ; en- 

 tirely free and disconnected ; of the normal number of segments, (2) — except in liissa. 



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. Flitmdge soft, close, thick; its colors simple — white, 

 black, brown, or pearl-blue predominating ; bright tints hardly found, excei)t ou 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 numer- 

 ous heavy dark blotches. Nidification normally terrestrial ; reproduction altrical ; 

 young ptilopiedic. 



Palate Avith a median and two lateral ridges, papillate. Nasal aperture long, linear, 

 its edges papillate. Opening of Eustacliiun tube conspicuous. Tongue fully formed, 

 lleshy, apicallj' more or less corneous and bifurcate, posteriorly bipartite, papillate. 

 Mouth capacious. 



(Esophagus capacious, muscular, very distensible, but stn;»ight, without permanent 

 dilatations, its mucous membrane longitudinally plicate. I'rorentriculns directly con- 

 tinuous with (esophagus, saccular; its glands simple follicles, forming a complete zo)ie. 

 Gigerinm nearly directly continuous with the proventriculus ; moderately muscular, its 

 cuticular lining dense, hard, rugose. Xo fully-formed pyloric valves. Duodenal fold 

 of ordinary character. Intestines of moderate length and calibre. Colon very short. 

 C'tt'ca coli always present, but extremely variable in length. A capacious globular 

 cloaca. A more or less perfectly developed urinary bursa. 



Lobes of liver unequal, connected loosely superiorly. No lobulus spigeJii. Pancreas 

 well developed. Hepatic and pancreatic ducts opening usually close together, at the 

 termination of the duodenal fold. Gall-bladder and spleen usually if not always pres- 

 ent ; the latter small, elongated. 



Kidneys more or less completely divided into lobules, especially in Sterninn: Open- 

 ings of ureters and vasa defereutia upon minute papiihe, side by side, on the fold of 

 mucous membrane sejiarating the two portions of the cloaca. No intromitteut male 

 organ. 



Opening of the glottis rather large, linear, its edges papillate. Superior larynx with 

 a median longitudinal internal crest. Tiachca straight, sini])le, without folds or dilata- 

 tions; llattcned above, cylindrical and smnller in calibre below; its rings cartilagi- 

 nous, numerous, closely apposed ; each varying in widtii from right to left successively. 

 Inferior larynx small and simple. Jlronciti of moderate and aliout ecpial length; an- 

 teriorly witli numerous rings, of unvarying width; posteriorly cut iri-ly membr.iuous. 



General osteology closely corres|iondent with ithat t)f PygojnnUs. No basiptery- 

 goid8(?), nor accessory ossicles in the elbow, nor tibial apophysis; no long bones llat- 

 tencd as in Sphenisci. 



The above characters define a natural group of birds found in every part of the 

 world. Kegarding the value of the gioup, however, and of its suVxlivisions. authors 

 are greatly at variance. It has usually hei'U held to be of fauiilv rank, and to com- 

 prise four subfamilies, with numerous genera. Again, it has been divided into two 



