1882.] FROM PERU AND CHILI. 529 



two well-uiaiked species, was probably, unless the direction of 

 currents has materially altered, by Humboldt's current northwards 

 to the equator, thence across the comparatively feeble and conflicting 

 equatorial currents, until the ilorth equatorial drift led to the shores 

 of Japan. 



On the coast of California occurs Larus heermanni, another mem- 

 ber of this group, with an entirely black tail, and a hood in tlie im- 

 matur-e state ; the head gets lighter with age, but the underparts 

 are washed with the dark grey so characteristic of Pacific forms. It 

 has no very close ally in existence ; for Larus niodestus, a much 

 slenderer Gull, restricted to the coasts of Peru and Chili, only re- 

 sembles it in the hood of immaturity and in general coloration, and 

 differs from it in having a tendency to lose the black markings on 

 the rectrices with advance in age. And the isolated Larus fuligi- 

 nosus, found only in the Galapagos group, differs from the other 

 Pacific Gulls in having a hood at all ages and in losing the markings 

 on the rectrices at maturity. It would seem as if this smoke-coloured 

 species, stranded at the Galapagos, might be the nearest living 

 representative of the ancestor of all these Pacific forms, and the one 

 which at the same time links them to the type of the northern hemi- 

 sphere. 



Between South America and the neighbourhood of New Zealand 

 and Australia only Terns are found, no Gull of any kind being on 

 record. Even L. dominicamts is absent from the South-Pacific 

 islands, its line of connexion between South America and New 

 Zealand being by the South Atlantic. But along the southern 

 shores of Australia, from King George's Sound to Tasmania, and 

 (according to the labels on the specimens obtained by the Antarctic 

 expedition) in New Zealand, is found a large dark-mantled Gull, 

 Larus pacificus. Lath., which has an immense blunt bill of peculiar 

 i'orm, somewhat like that of L. scoresbii, and further resembles the 

 Pacific group in that the adult has a broad black band across the 

 rectrices. It is an isolated form ; but although it mav be difficult 

 to explain its existence at the junction of the waters of the South 

 Pacific and South Atlantic, the fact seems worthy of attention. 



Apart from conjectures, there can be no doubt that the connexion 

 between the pelagic birds of the northern and southern hemispheres 

 is much closer in the Pacific than in the Atlantic. The closer 

 resemblance between Stercorarius catarrhactes and *S'. chilensis than 

 between the latter and its present near neighbour, S. antarcticus, is 

 one proof of this ; the intermediate position occupied by Sterna 

 uleutica of the Aleutian Islands, between the ordinary type of north- 

 ern Tern and the intertropical group of sooty Terns, is still further 

 evidence ; but the strongest of all is perhaps in the case of Xema 

 sabinii and X. furcatum. The former, a circumpolar species not 

 known to breed south of the arctic circle, except on the shores of 

 Behriug's Sea, extends its breeding-range in the North Pacific as far 

 south as Alaska ; and not only the young birds, which are always 

 great wanderers, but also the adults of this species come down in 

 winter as far as 12° S. lat, thus considerably overlapping the range 



