516 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.49. 



The names of colors used are from Mr, Ridgway's recent "Color 

 Standards and Color Nomenclature." 



The geographical distribution of TTidlasseus hergii is extensive, and 

 almost whoUy littoral, reaching north to the Marshall Islands, the 

 Riu Kiu Islands of Japan, southern China, northern India, the 

 Persian Gulf, and the Red Sea; west to the Red Sea and German 

 Southwest Africa; south to the Cape of Good Hope, Madagascar, 

 Rodriguez Island, Ceylon, Sumatra, Java, southwestern Australia, 

 Tasmania, the Tonga Islands, and the Society Islands; east to the 

 Paumotu Islands, and the Marquesas Islands. It is also of casual 

 occurrence in Palestine. Over its regular range it seems to be 

 resident throughout the year. 



This species is reaUy a difficult one, and presents much variation 

 of both size and color to trouble the systematist; but, notwithstand- 

 ing this, it is possible to recognize at least 11 subspecies, though 

 most of them, it is true, rest on average characters. Much to reduce 

 this number, however, as Mr. Stresemann has done, merely serves 

 to increase rather than to decrease the difficulty; for the latitude of 

 individual variation which such an arrangement allows many of the 

 forms is so great as widely to overlap and seriously impair the assign- 

 able characters of some of the other forms which are current and 

 certainly worthy of recognition by name. Although there is con- 

 siderable individual variation in both size and color in most of the 

 subspecies admitted in the following pages, this variation does not 

 obliterate the usually well-marked average characters of a given race. 

 Notwithstanding this individual variation there seems to be httle or 

 no sexual difference, which happpily renders unnecessary separate 

 comparisons of male and female. 



The Juvenal plumage varies considerably from that of the adult, 

 as foUows: Whole pileum streaked with brown; occipital crest dull 

 dark brown; upper parts, including superior wdng-coverts, dull 

 brown mottled with white; tail mostly dark brown, the feathers 

 tipped with white; and dark portions of wing-quills dull dark brown. 



The present species, together with several others closely allied, 

 are without much doubt generically distinct from the members of 

 the true genus Sterna, the type of which is Sterna hirundo Linnaeus. 

 The structural differences separating Sterna hergii from Sterna hi' . 

 rundo consist chiefly in relatively shorter tail, this not over half the > 

 length of wing; relatively longer biU, this at least two-elevenths of 

 the length of the wing; stouter bOl; less prominent angle of gonys, 

 the height of biU through this angle being decidedly less than at 

 the anterior end of nostril, while in Sterna it is practically the same; 

 and the presence of an occipital crest of pointed feathers. 



The generic name to be applied to the group including Sterna hergii 

 has been somewhat in dispute, for it involves the question of the right 



