396 MR. H. SAUNDERS ON THE GEOaRAPHICAL 



Lawr., the largest member of the group of which L. zonorhynelius, 

 Ord, is its nearest ally in the Nearctic region ; and again, over a 

 similar area is found L. IrachyrliyncJius, Richards., the close ally 

 and representative in North-western America of L. canus of the 

 whole Palaearctic region from Europe to Japan. These three 

 species seem to keep to their respective sides of the North 

 Pacific ; and if we excej^t stragglers of L. californicus and L. zo- 

 norhyncJius to Japan, and of L. canus to Labrador, these inhabi- 

 tants of the Nearctic and the Palaearctic regions do not appear to 

 overlap ; nevertheless the North Pacific is the only area within 

 which they are all found, and seems in this case also to be the 

 point of dispersal. This brings us to the consideration of another 

 natural group, the members of which occur throughout the whole 

 of the Pacific, both north and south, but more particularly in 

 the latter. 



In the typical Gulls the barred tail is a mark of immaturity, and 

 the hood is usually the sign of breeding plumage ; but there is a 

 group in which these conditions are partially or entirely reversed. 

 The coasts of China and Japan are frequented by L. crassirostris, 

 Vieill., a medium-sized gull, which has a slight tendency to a 

 brownish hood when young, but which in the adzolt state has a pure 

 white head and underparts, a dark grey mantle, and a tail crossed by 

 a broad black bar. On the Calif ornian side is found L. Jieermanni, 

 of about the same size, with a still more distinct hood in the imma- 

 ture stage, w^ith more black on the tail, and underparts of a sooty 

 grey colour, which fades away on the head into a pale grey in the 

 fully adult. Tet further south, on the coasts of Peru and Chili, is 

 L. helc}ieri,Yigor8, a stout^billed gull, with a very marked hood in 

 the early stage, but which when adult is much like L. crassirostris, 

 except that its mantle is decidedly black. On the same coasts 

 occurs a much slenderer and more elegant species, L. modestus, 

 Tsch., with rather delicate tarsi ; this also has a decided hood 

 when immature, but in the adult the dark grey of the underparts 

 fades into a pale colour, and becomes almost white on the head 

 and forehead. In the Gralapagos archipelago, and nowhere else, 

 is found a much stouter and coarser gull, L.fuliginosus, Gould, 

 of a nearly uniform sooty hue, and bearing a hood in the adult as 

 well as in the immature plumage. At the very extremity of the 

 district, and extending some distance beyond it, ranging from the 

 Straits of Magellan to the Palklands and South Shetland Islands, 

 comes an aberrant species, of which it cau only be said that its 



