58 HISTORY OF 



these birds is much lighter than that of Larus ; they generally 

 feed on the edge of the water, sometimes wading, for which 

 their partially naked thighs peculiarly adapt them. 



Of the four sub genera into which we propose to divide the 

 Gulls, perhaps that of Rissa, Leach, containing the Kittiwake, 

 conies nearest to Lestris. We shall therefore place it first, 

 and Xema, Leach, last, as coming nearest to the Terns, (Genus 

 Sterna, Linn.) The subdivisions of the genus Larus, therefore, 

 will stand thus : 



Sub gen. 1. Rissa, Leach. 



Wanting the hind toe ; tarsi, moderate. 



2. Larus, Stephens. 



Hind toe, perfect ; tarsi, strong ; thighs, fea- 

 thered, nearly to the joints; head, white in 

 the summer and winter plumage ; tail, 

 rounded. 



3. Chroicocephalus, Nobis. 



Hind toe, perfect ; tarsi, slender ; thighs, much 

 denuded ; tail, rounded ; head, dark coloured 

 in the summer plumage. 



4. Xema, Leach. 



Tail, forked. 



