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Show 522 MR. H. SAUNDERS ON LARIDJE [June 6, STERNA HIRUNDINACEA, Less. Sterna hirundinacea, Lesson, Tr. d'Orn. p. 621 (1831) ; Saund. P.Z.S. 1876, p. 647. Sterna cassinii, Scl. P. Z. S. I860, p. 391; Scl. & 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 recorded (Cunningham, 'Ibis,' 1870, p. 500). The head-quarters of this southern species are on the coasts and islands of tbe Chilian archipelago, the Straits of Magellan, Patagonia, and the Falkland Islands; but on the Atlantic side of the continent its range northwards is not known to extend beyond Rio de Janeiro, in 23° S. lat. STERNA EXILIS, Tsch. Sterna 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 subdivision. It is a purely South-Pacific species, which may be briefly described as a long-winged S. minuta, 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 melanuru, Swainson, An. in Menag. p. 340 (1838). [No. 66($), Coquimbo Bay, November 1881. Eves brown.] Adult. In their excellent treatise on the Neotropical Laridse (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 fact that, amongst Mr. Salvin's white-tailed specimens 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 extensive 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 |