522 . MR. H. SAUNDERS ON LARID^ [JuDB 6, 



Sterna hirundinacea, Less. 



Sterna hirundinacea, Lesson, Tr. d'Oni. p. 621 (1831); Saund. 

 P.Z. S. 1876, p. 647. 



Sterna cassinii, Scl. P. Z. S. 1860, p. 391 ; Sd. & Salv. op. cit. 

 1871, p. 570. 



[No. 30 (juv.), no. 31 (adult), Callao Bay, August 1881 ; nos. 35 & 

 36 (juv.), Coquimbo Bay, Nov. 1881. Eyes dark brown.] 



One adult, and three birds of the year in progressive stages of 

 winter plumage. Callao, in 12° S. lat., is a considerable advance of 

 range over that of Coquimbo in 30" S., the furthest previously re- 

 corded (Cunningham, 'Ibis,' 1870, p. 500). The head-quarters of 

 this southern species are on the coasts and islands of the Chilian 

 archipelago, the Straits of Magellan, Patagonia, and the Falkland 

 Islands ; but on the Atlantic side of the continent its range north- 

 wards is not known to extend beyond Rio de Janeiro, in 23° S. lat. 



Sterna exilis, Tsch. 



Sterim exilis, Tschudi, F. Per. Aves, p. 306 (1846); Scl. & 

 Salv. P. Z. S. 1871, p. 572 ; Saund. op. cit. 1876, p. 663. 



[Nos. 37 & 38, Paracas Bay, Peru, October, 1881. Eyes brown.] 



I have now examined five, and possess three specimens of this 

 very distinct, although little-known member of the Sternula sub- 

 division. 



It is a purely South-Pacific species, which may be briefly described 

 as a long-winged S. rninuta, washed all over with shades of smoke- 

 grey, and with more black on the bill. Its immature plumage and 

 its breeding-places are still unknown. 



Rhynchops melanura, Sw. 



Rhynchops melanura, Swainsou, An. in Menag. p. 340 (1838). 



[No. 66 ( $ ), Coquimbo Bay, November 1881. Eyes brown.] 

 Adult. 



In their excellent treatise on the Neotropical Laridae (P. Z. S. 

 1871, p. 566) Messrs. Sclater and Salvin deemed it advisable to 

 unite under the specific name of R. nigra both the northern white- 

 tailed form and the southern black-tailed one. This caution was 

 mainly due to the tact that, amongst Mr. Salvin's white-tailed spe- 

 cimens obtained during winter in Central America, one example 

 shows some dark markings in the middle of the lateral rectrices, 

 thus intergrading with the southern dark-tailed bird. Recent 

 examination of this specimen and the others in Mr. Salvin's exten- 

 sive series, besides my own, leads me to the conclusion that the 

 two forms are entitled to specific distinction, for the following 

 reasons : — In the northern adult the upperside of the rectrices is 

 almost entirely white, with only a little dusky colour in the central 

 ones, the underside being pure white ; the under wing-coverts are 

 white ; the secondaries are to a great extent white, and the upper 

 primaries show a considerable margination of that colour. In 

 the southern form, on the other hand, the rectrices on both their 



