24; LARID^. 



p. V (1852) ; Licht. Nommcl. Av. p. 98 (1854) ; Bp. C. JR. xlii. 

 p. 772 (1856) ; Scl. S,- Salv. P. Z. S. 1871, p. 567, 1873, p. 310 

 (Eastern Peru) ; iid. Nomencl. Av. Neotrop. p. 147 (1873) ; Ber- 

 lepsch, J.f. O. 1874, p. 278 (Santa Catharina) ; Bumf. Ibis, 1877, 

 p. 200 (Buenos Aires) ; Taczan. ^- Berlepsch, P. Z. S. 1885, p. 112 

 (Riobamba, Ecuador) ; Scl. ^- Huds. Argent. Orn. ii. p. 194 (1889) ; 

 Heim 4" Peichen. Nomencl. Mus. Hein. p. 355 (1890) ; Scl. P. Z. S. 

 1891, p. 301 (alive at Zool. Gardens). 



Thalassites magnirostris, Sto. Classif. B. ii. p. 372 (1837) ; Scl. ^ Salv. 

 P. Z. S. 1866, p. 200 (Lower Ucayali). 



Thalasseus chloripoda ( Vieill), Boie, Isis, 1844, p. 182. 



Sylochelidon speculifera, Boie, Isis, 1844, p. 186. 



Sylochelidon magnirostris. Gray, List Anseres in Brit. Mus. p. 175 

 (1844) ; Bias. J.f. 0. 1866, p. 82. 



Sterna albifrons, Cuv. MSS. in Mus. Paris ; Pucheran, Rev. Zool. ii. 

 p. 344(1850)*. 



Sterna chloripoda, Leot. Ois. Trinid. p. 537 (1866). 



Adult. Head and nape glossy black, with a very narrow line of 

 white at the base of the bill ; nape and sides of neck pale grey ; 

 mantle and tail slate-grey ; carpal coverts, upper wing-coverts, and 

 the greater part of secondaries white ; primaries dark brown, with 

 whitish " wedges " to the inner webs and narrow white borders to 

 the inner margins (increasing on the upper primaries) ; shafts 

 blackish ; inner secondaries broadly edged with white and grey, 

 with a brownish spot above ; lores, cheeks, and underparts pure 

 white. In less mature birds the white on the forehead is a little 

 wider ; the mantle has a browner tinge ; the brown spots on the 

 inner secondaries are more extensive, and the lores are slightly 

 flecked with black ; but there does not seem to be any distinct 

 winter or '• eclipse" stage beyond a slight mottling of the crown. 

 The sexes appear to be alike in plumage. Bill chrome-yellow, 

 slightly greenish at the base of the lower mandible ; feet olive, the 

 webs yellow. Total length 14-75 inches, culmen 2"8, wing 11"5, 

 tail 4*8, the fork only 0*6 deep, tarsus 1, middle toe and claw 

 1-15. 



Immature. Crown slate-grey ; a blackish patch from the back of 

 the eye to the nape, which is also blackish ; bill with a greener 

 tinge ; otherwise like the adult. 



Young. Crown at first pale brown, streaked with umber, after- 

 wards grey ; upper parts greyish, mottled with brown and drab ; 

 upper tail-coverts and tail slightly barred and tipped with dull 

 white or drab. 



Hab. Trinidad and the Orinoco to the Parana and the La Plata, 

 and on the large rivers of tropical South America up to the foot of 

 the Andes ; also on the estuarine coasts of Peru and Ecuador. 

 Eggs deposited on sand-banks. 



a. Ad. St. " South America." Zool. Soc. Mus. [P.]. 



b. Ad. sk. South America. Gould Coll. 



c. Imm. sk. British Guiana. Sir R. Schomburgk [P.]. 



* Type examined. 



