292 PROCEEDINGS OF THE ACADEMY OF 



As some time, however, may elapse before the appearance of the Report, it 

 has been thought advisable to issue in advance this brief sketch of the sub- 

 ject. Except in the cases of one or two species, everything not absolutely 

 necessary to the proper understanding of the subject has been omitted. In 

 the Monograph alluded to will be found references to the pages of the works 

 of the authors cited ; descriptions of the various changes and stages of plu- 

 mage ; together with a discussion of doubtful points of synonymy, and the 

 arguments for the views entertained. It is also illustrated by figures of the 

 bills of all the species, and colored drawings of the primary quills, showing 

 the outlines and extent of their markings. The gulls of North America are 

 worked up to the fullest extent that the specimens at my command allow ; 

 but, in the apparent hopelessness of arriving at ultimate truth with regard 

 to these birds, I am prepared to relinquish any of the views now entertained 

 which future investigation may prove to be erroneous. 



Family L&RIDJE. 



The family Laridse, embracing the Jagers, Gulls, Terns and Skimmers is 

 divisible into four subfamilies, which may be distinguished by the following 

 brief diagnosis : 



LESTRinraiE. Covering of upper mandible not continuous, the basal half 

 with a somewhat horny overlapping plate, differing in character from the ter- 

 minal portion ; the nostrils opening beneath it, but slightly above the cutting 

 edge, and beyond the middle of the bill. Tail cuneate, the central feathers 

 projecting, usually tapering and much elongated, the lateral stiff and acu- 

 minate. Interdigital webs more or less rounded. Body full, stout ; size 

 usually moderate. 



LarinjE. Covering of bill continuous. Bill more or less robust, the culmen 

 about straight to the nostrils, abruptly decurved to the tip, which overhangs 

 the tip of the lower mandible. An angular projection at the symphysis of 

 the lower jaw more or less prominent. Nostrils at the end of the basal half 

 of the bill. Tail generally even, the feathers being all of the same character. 

 Webs more or less indented. Inner lateral toe moderate. Body robust ; size 

 very large or moderate. 



Sterninje. Covering of bill continuous. Bill slender and tapering to a 

 very acute point, the tip not abruptly decurved, nor overhanging the lower 

 mandible. Curve of culmen and commissure regular and gradual from base 

 to tip. Angle of lower mandible scarcely apparent. Nostrils on the basal 

 third of the" bill. First primary greatly longer than the second. Tail gene- 

 rally forked. Inner lateral toes very short. Webs indented. Body rather 

 slender and graceful ; size moderate or very small. 



RHYKcnopsiNiE. Bill excessively compressed, like the blade of a knife. 

 Upper mandible abruptly shorter than the lower. Otherwise generally as in 

 Sternino . 



We have at present only to do with the second of these groups, the 



Subfamily LARIN.E. 



Of the many genera into which the Gulls have been divided by systematic 

 writers, North America contains representatives of eight, which seem to differ 

 in well marked characters. They may be arranged in two sections and very 

 briefly defined as follows : 



A. Lareje. 



Size very large, large, or moderate. Body robust, general organization 

 more or less powerful. Bill stout and deep, the angle prominent, the tip ob- 

 tuse, seldom attenuated or much decurved. Tail never cuneate or decidedly 



[June, 



