140 BULLETIN 133^ UNITED STATES NATIONAL MUSEUM 



the small indentation of the Bahia de Samborombon into which it 

 opens, below Lavalle, Buenos Aires. On January 9, 1921, 40 or 

 more were recorded at Carrasco, a bathing resort a few kilometers 

 east of Montevideo, Uruguay, and on January 16 others were seen 

 in the same locality. The male secured had the soft parts colored 

 as follows: Bill, between flesh-ocher and rufous; iris, natal brown; 

 tarsus, black with a few of the scutes marked with vinaceous russet ; 

 underside of toes, ochraceous orange. The bird was in full plumage. 



PHAETUSA SIMPLEX CHLOROPODA (Vieillot) 



Sterna chloropoda Vieillot, Nouv. Diet. Hist. Nat., vol. 32, 1819, p. 171. 

 (Paraguay.) 



The large-billed tern was fairly common near the Rio Paraguay. 

 At Las Palmas, Chaco, it was seen in small numbers about lagoons 

 from July 23 to 31. On July 26 two were observed resting on a flat 

 clump of grass and one, an adult female, was taken. At Puerto 

 Pinasco several were observed over the Paraguay River on Septenj- 

 ber 3, and from September 6 to 21 occasional birds were recorded 

 west of that point at lagoons near the ranch at Kilometer 80. They 

 were seen frequently in steamer travel along the river, the last being 

 noted at Villa Concepcion, Paragua}^, on October 3. 



These birds on the wing appear more robust than other terns, an 

 appearance heightened by the strong, heavy bill. They frequenth' 

 swing up to an intruder and examine him curiously or scold vigor- 

 ously with harsh raucous calls. At such times the light-colored bill 

 is prominent. 



The soft parts in the adult female secured were colored as follows : 

 Bill lemon chrome, becoming light cadmium at base of culmen; 

 tongue and inside of bill lemon chrome, becoming cress green toward 

 the fauces ; iris fuscous ; tarsus and toes primuline yellow ; claws dull 

 black at tip, changing at base to gray number 7. 



Large-billed terns from the northern portion of South America 

 have the upper surface varying from darker than neutral gray to 

 dark neutral gray, while in specimens from Paraguay and northern 

 Argentina (Chaco) the hind neck, back, scapulars, lesser wing 

 coverts, and tail are between light neutral gray and neutral gray. 

 The evident differences separate birds from the two regions as well- 

 marked subspecies. 



/Sterna simplex of Gmelin ^^ has been referred doubtfully to the 

 present species by several writers. It is based on the simple tern of 

 Latham ^^ from Cayenne. Turning to the original citation in 

 Latham it is found that the bird described is evidently in immature 

 plumage. The points given agree perfectly with those of the young 



18 Syst. Nat., vol. 1, pt. 2, 1789, p. 606. 



'9 Gen. Syn. Birds, vol. 3, pt. 2, 1785, p. 355. 



