550 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
Gavia] leucoceps Swanson, Classif. Birds, ii, 1837, 373 (Louisiana; based on 
Mouette brune, de la Louisiane Daubenton, Pl. Enl., pl. 997). 
A{nous] leucoceps Gray, Gen. Birds, iii, 1846, 661. 
(2?) Anous melanogenys (not of Gray, 1846) Ltoraup, Ois. Trinidad, 1866, 547. 
Anous superciliosus SHARPE, Philos. Trans., clxviii, 1879, 468 (coast of Central 
America and the Antilles). ‘ 
ANOUS STOLIDUS RIDGWAYI Anthony. 
SOCORRO NODDY. 
Similar to A. s. stolidus but coloration slightly darker, the pileum 
darker gray, becoming white only on anterior margins.* 
Adult male-—Wing, 261.5-292 (272.6); tail, 142-169 (160.5); ex- 
posed culmen, 41-43.5 (41.9); tarsus, 23-26 (24.6); middle toe, 
30-34 (31.3).? 
Adult female—Wing, 265-283 (272.6); tail, 141.5-162 (151.1); 
exposed: culmen, 38-43 (40.8); tarsus, 23-26 (24.2); middle toe, 
29-32 (30.8).¢ 
Pacific coast of Mexico, from Tres Marias Islands and Isabella 
Island, Tepic, to coast of Guatemala, Socorro Island, Revillagigedo 
group, Clipperton Island, and Cocos Island. 
Anous stolidus (not Sterna stolida Linneus) SctaTer and Savin, Ibis, 1859, 233 
(Pacific coast Guatemala).—Lawrence, Mem. Bost. Soc. N. H., ii, 1874, 318 
(Isabella Island, Tepic, n. w. Mexico, breeding; habits; descr. nest and 
eggs).—Barrp, Brewer, and Ripaway, Water Birds N. Am., ii, 1884, 325, 
part (Pacific coast Central America).—TownsENnD, Bull. Mus. Comp. Zool., 
xxvii, 1895, 125 (Cocos Island, Costa Rica; crit.).—Carrixer, An. Carnegie 
Mus., vi, 1910, 415 (Cocos Island).—Gurrorp, Proc. Calif. Ac. Sci., 4th ser., 
ii, pt. i, 1913, 24, part (Clipperton and Cocos islands). 
Anous stolidus ridgwayi ANTHONY, Auk, xv, no. 1, Jan., 1898, 36 (Socorro 
Island, Revillagigedo group, off w. Mexico; coll. A. W. Anthony); no. 4, 
Oct., 1898, 316 (Socorro Island).—Netson, North Am. Fauna, no. 14, 1899, 
26 (Tres Marias, May; Isabella Island, May; between San Blas and Tres 
Marias; habits)—Snopcrass and Herter, Proc. Wash. Ac. Sci., iv, 
1902, 507 (Clipperton and Cocos islands; descr., measurements; habits; 
descr. eggs).—_Matuews, Birds Australia, ii, 1912, 411 (Socorro; Tres Marias). 
[Anous] stolidus subsp. ridgwayi Forses and Rosrinson, Bull. Liverp. Mus., ii, 
no. 2, 1899, 56 (reprint of orig. descr.). 
[Anous] ridgwayi SHarrE, Hand-list, i, 1899, 137. 
Anous pileatus (not Sterna pileata Scopoli, 1786) Satvin and Gopman, Biol. 
Centr.-Am., Aves, iii, 1908, 661, part, excl. syn. (Isabella, Tres Marias, and 
Clipperton islands; Pacific coast Guatemala). 
@ So far as the material examined enables me.to judge, typical specimens of this 
form are confined to Socorro, Clipperton, and Cocos islands; at any rate, examples 
from Isabella island, off Tepic, and from the coast of Guerrero (Sihuatenejo) are in 
‘coloration more like A. s. stolidus; in fact, some of them I am not able to distinguish 
satisfactorily from that form. 
b Nine specimens. 
¢ Highteen specimens. 
