BIRDS OF NORTH AND MIDDLE AMERICA. 



557 



Adult male.—Wmg, 216-241 (232); tail, 112-132 (124); culmen, 

 40-48.4 (44.7); depth of bill at base, 8-10.6 (9); tarsus, 19.2-21.6 

 (20.2); middle toe, 26.5-28.9 (27.8).'^ 



Advlt female. —Wing, 212-246 (229); tail, 111-129 (121); culmen, 

 37.1-42.4 (42.2); depth of bill at base, 7-10.2 (8.4); tarsus, 18.1- 

 20.5 (19.7); middle toe, 25-29.5 (27.5).^ 



Off Pacific coast of Central America, breeding on Clipperton and 

 Cocos Islands. 



Micranous diamesus Heller and Snodgrass, Condor, iii, May, 1901, 76 (Cocoa 

 Island; coll. Leland Stanford Jr. Univ.). — Snodgrass and Heller, Proc. 

 Wash. Acad. Sci.. iv, 1902, 509 (Cocos and Clipperton islands; descr. ; crit., 

 measurements). — Gifford, Proc. Calif. Acad. Sci., 4th ser., ii, pt. i, 1913, 

 29 (breeding on Clipperton and Cocos islands; habits, measurements, etc.), 

 113 (measurements). 



Megalopterus minutus diamesus Mathews, Birds of Aut-tralia, ii, pt. 4, Nov. 1, 

 1912, 423. 



Genus GYGIS Wagler. 



Gycjis (not Gyqes Bory de Sit. Vincent, 1825) Wagler, Isis, xxv, 1832, 1223. 



(Type, by original designation and monotypy, Sterna Candida Gmelin= 



S. alba Sparrman.) 

 Leucanous <^ Mathews, Birds Australia, ii, pt. 4, Nov. 1, 1912, 432, in text. 



(Type, by original designation, Gyciis mia'orhyncha Saunders.) 

 Alphagygisd Mathews, Austral. Avian Rec, ii no. 5, Sept. 24, 1914, 110. 



(Substitute for Gygis Wagler, 1832, considered as preoccupied by Gyges 



Bory de St. Vincent, 1825.) 



Rather small Sternidae (wing 218-251 mm.) with wholly white 

 coloration, cuneate, straight-tipped bill, deeply excised webs, and 

 tail both forked and graduated. 



Bill about as long as head, compressed and cuneate terminally 

 and relatively deep basaUy; exposed culmen longer than tarsus and 



a Twenty -six specimens. 

 * Thirty specimens. 



(The above measurements are from Gifford, Proc. Calif. Acad. Sci., 4th ser., ii, pt. i, 

 1913, 32, 113.) 



c AefiKos, white4--4noMS [apovs, foolish). (Mathews.) 

 <* 'A\<i>a, &T9t-\-Gygis (yOyrjs, a fabulous bird); Mathews. 



