276 LONG-WINGED SWIMMERS — LONGIPENNES. 



D. Size small (wing less than 11.00 inches, and more than 8.00) ; tail excessively linked, the 



lateral rectrices attenuated ; 1 occipital feathers soft, blended, not forming a crest ; inner 

 webs of primaries bicolored ; adult pearl-blue above, white, pale pink, or grayish beneath; 

 pileum wholly deep black in summer, except in Trudcaui (whole head white, with a lateral 

 dusky bar) and aleutica (white frontal lunule). (Sterna, Linn.) 

 re. Pileum entirely white in summer. 



6. S. Trudeaui. Bill black, tipped with yellowish ; head white, with a dusky lateral bar ; 



upper and lower parts pale pearl-gray ; rump, tail-coverts, and tail white, slightly silvered. 

 Wing, 9.70-10.60 inches; tail, 4.60-6.00; culmen, 1.50-1.70; tarsus, .92-.96 ; middle 

 toe, .75-.80. Hab. Coasts of South America, and casual along the Atlantic coast of the 

 United States. 

 6. Pileum entirely black in summer. 



7. S. Forsteri. Bill dull orange, dusky at the tip ; feet rich orange-red (in life) ; outer web 



of lateral rectrices pure white throughout, the inner web usually dusky or grayish toward 

 the end, in more or less marked contrast ; 2 lower parts entirely white. Wing, 9.50-10.30 

 inches; tail, 5.00-7.70 ; culmen, 1.50-1.65; tarsus, .90-99 ; middle toe, 1.05-1.15. Ilab. 

 Temperate North America in general, south in winter to Brazil. 



8. S. hirundo. Bill vermilion, the tip dusky ; feet rich vermilion (in life) ; outer web of 



lateral rectrices grayish or dusky, the inner pure white throughout, in abrupt contrast ; 

 lower parts usually pale grayish, rarely nearly white. Wing, 9.75-11.75 inches; tail, 

 5.(10-7.00; culmen, 1.25-1.50 ; tarsus, .66-.87 ; middle toe, .75. Hab. Eastern North 

 America ; Pala?arctic Region. 



9. S. paradisaea. Bill rich carmine, with or without black tip ; feet intense red (in life) ; 



outer rectrices as in fluviatilis, but usually more elongated ; lower parts deep, somewhat 

 smoky, pearl-gray, almost as dark as the upper parts. Wing, 10.00-10.75 inches ; tail, 

 6.50-8.50; culmen, 1.08-1.40; tarsus, .55-65; middle toe, with claw, .80-85. Hah. 

 Northern parts of northern hemisphere. 



10. S. Dougalli. Bill black, usually reddish basally ; feet bright red (in life) ; lateral 

 rectrices wholly white, sometimes very faintly silvered ; lower parts delicate peach- 

 blossom-pink in life, fading to pinkish white or even pure white in the dried skin. Wing. 

 9.25-9.75 inches; tail, 7.25-7.75; culmen, 1.50; tarsus, .85; middle toe, .75. Hab. 

 Atlantic coast of North America ; West Indies ; Palrcarctic Region. 



c. Forehead white, this color extending back along the sides of the crown to the eyes. 



11. S. aleutica. Bill and feet wholly deep black ; upper parts pearly plumbeous, the upper 

 tail-coverts and tail abruptly pure white ; lower parts paler plumbeous, fading into white 

 on the chin and crissum. Wing, 9.75-10.75 inches ; tail, 6.50-7.00 ; culmen, 1.25-1.40 ; 

 tarsus, .60-75 ; middle toe, .80-85. Hab. Coasts and islands of Alaska. 



E. Size extremely small (wing less than 8.00 inches) ; tail moderately forked, the lateral feathers 



not much attenuated ; occipital feathers soft and blended. Adult pale pearl-blue above, 

 the rump and tail sometimes white ; white beneath ; the pileum with a white frontal 

 lunule, as in Sterna aleutica and in HaUplana. (Sternula, Boie.) 



12. S. antillarum. Bill yellow, usually lipped with black ; upper parts entirely pale pearl- 

 blue, including the tail ; lower parts white ; wingless than 7.00 inches ; culmen less than 

 1.25; the bill usually black-tipped. Hab. Warm-temperate North America and Middle 

 America ; West Indies. 



F. Size small (wing about 10.50 to 12.00 inches) ; bill very straight, the culmen sometimes even 



slightly depressed in the middle portion ; nasal groove long and deep, the nostrils more 

 anterior than in Sterna : tail deeply forked, but the feathers relatively broader and 

 stiller ; color, dusky above, sometimes interrupted by a whitish nuchal band ; beneath, 

 entirely white ; pileum black, with a white frontal lunule as in Sternula and in Sterna 

 aleutica. (HaUplana, Wagler.) 



13. S. fuliginosa. Above, entirely brownish black, uninterrupted on the nape ; wing, about 

 12.00 inches. Hab. Sea-coasts throughout the warmer parts of the world ; in North 



1 When fully developed, and not abraded. 



2 This latter feature by no means constant, however. 



