GELOCHELIDO:v\— HTDEOPEOGNE. 401 



as a lining. The eggs are generally three, rarely four, in number; they are of a 

 broad oval shape, the ground-colour varying from a greyish- or huffish-white to a pale 

 buff, stone-colour, or brown ; the markings are of small size and evenly distributed 

 over the shell, consisting of spots and blotches of dark brown or olive-brown, with very 

 prominent underlying grey ^^. 



HYDROPROGNE. 



Hydroprogne, Kaup, Natiirl. Syst. p. 91 (1829) ; Saunders, Cat. Birds Brit. Mus. xxv. p. 32 

 (1896). 



The single species of the genus Hydroprogne is a bird of large dimensions, with a 

 red bill of exceptional size, stoutness, and depth. Tail very short, being less than 

 one-third of the wing ; the outer tail-feathers are the longest and are pointed. Tarsus 

 short, being less than the length of the middle toe and claw. H. caspia is found in 

 nearly all temperate and tropical regions. 



1. Hydroprogne caspia. 



Sterna caspia, Pall. N. Comm. Petrop. xiv. 1, p. 582, t. 22. fig. 2 ' ; Baird, Brewer, & Ridgway, 



Water-Birds N. Amer. ii. p. 280 '. 

 Hydroprogne caspia, Saunders, Cat. Birds Brit. Mus. xxv. p. 33 ' ; Gates, Cat. Eggs Brit. ]Mus. i. 



p. 178 \ 

 Sterna tschegrava, A. O. U. Cheek-1. N. Amer. Birds, p. 23 \ 



Ptil. cESiiv. Maxima : supra delicate margaritaceo-cinerea ; rectricibus dorso concoloribus, intus et ad 

 apicem albis ; alis dorso concoloribus, secundariis intus albidioribus, primariis saturatioribus, intus vix 

 nigricantibus, juxta rbachidem albam et pogonio externo scbistaceis ; pileo nuchaque cum loris dimi- 

 diatis et plumis subocularibus virescenti-nigerrimis ; macula suboculari alba ; loris inferioribus, facie 

 laterali et corpore subtus toto pure albis: rostro miniato, interdum apicem versus corneo; pedibus 

 nigris ; iride saturate brunnea. Long, tota circa 200, alae 17"2, caudae 4'2, rectriee extima 5-7, culm. i!y, 

 tarsi 1'6. (Descr. maris adulti ex Corpus Christi. Mus. nostr.) 



Ptil. Mem. Ptilosi sestivse similis, sed pileo nigro, albo maculato et linealiter striate. Long, tota circa 21-0, 

 alee 16*0. (Descr. maris adulti ex Presidio. Mus. nostr.) 



Hah. NoKTH Amjskica, from a little beyond the Arctic Circle, breeding southward to 

 Virginia, Lake Michigan, Texas, Nevada, and California ^ ^. — Mexico, Mazatlan, 

 Presidio {Forrer ^). — Eueope from about 60° N. lat. southwards ; Asia to China ^ ; 

 Malatasia to Australia and New Zealand ^ ; Africa ^. 



In Central America this bird can be scarcely more than a winter visitor, two 

 specimens only having been procured near Mazatlan by Mr. Forrer, one in December 

 and another in February ^. 



It is chiefly an inhabitant of the sea-shores and adjacent islands, but is also found 

 on inland seas and lakes. Its eggs, laid in a depression of the sand, are similar to 

 those of the Gull-billed Tern, but larger *. 



BIOL. CENTB.-AMER., Aves, Vol. III., November 1903. 51 



