454 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
posterior ones), and usually (%) with more of brownish gray on 
median portion of lateral rectrices.* 
Adult male.—Wing, 385~412 (402.8); tail, 112-133.5 (124.3); cul- 
men, 74-83.5 (78.7); greatest depth of bill, 28.5-31 (29.8); tarsus, 
33.5-37 (34.7); middle toe, 20.5-25 (23.3).° 
. Adult female.—Wing, 382; tail, 119.5; culmen, 66; greatest depth of 
pill, 24.5; tarsus, 28; middle toe, 17.° 
Seacoasts and larger inland waters of southern Brazil (Sao Paulo; 
Iguapé, Sao Paulo; Santa Catarina; Rio Araguaya; Espirito Santo), 
Paraguay (Rio Pilcomayo; La Paz, Jan. 29; Gran Chaco), Uruguay, 
and Argentina (Buenos Aires; Conchitas, Buenos Aires; Avellaneda; 
Rio Paran4); also, Pacific coast of Mexico and Central America (San 
Blas, Tepic; Rio Zacatula, Colima, April; Manzanillo, Colima, Feb. 11; 
San Mateo, Oaxaca?; Acapim, Guatemala, Jan.).¢ 
cAn adult male from Paraguay, which in large size agrees closely with this form, 
hhas the under wing-coverts wholly pure white and has no more gray on the lateral 
rectrices than some specimens of R. n. nigra. 
6 Six specimens. 
¢ One specimen. 
or 
. : a. ||, Cae: |. 88 Middle 
Locality. Wing. | Tail. depth | Tarsus. 
men. BF toe. 
bill. 
MALES. 
‘Three adult males of R. n. intercedens Paraguay (2) 
and southern Brazil (1).....-....-....2..02.2.222e ee 408.3 | 128.5 82 30.5 34, 2 22.7 
Three adult males of R. n. intercedens from Pacific 
coast of Mexico (2) and Guatemala(1)................ 396.3 | 120.2 75.5 29, 2 35.3 24 
Tenadult males of R. n. nigra........2..-.--.222eeeee 381.7] 124.3] 681] 281] 32.9 22.6 
Two presumed adult males of R. cinergscens .........-- 413.3 | 123.8) 87.2] 31.3] 36 23.8 
FEMALES. 
Oneadult female of R. n. intercedens from Argentina....| 382 119.5 66 24.5 28 17 
Four adult females of R. n. niyra........2.2.2.2.0.000- 346 106.6 55 22.9 27.6 18.4 
Seven presumed adult females of R. cinerascens ....... 377 117.4 67.1 24.9 35.7 20.7 
Unfortunately none of the specimens of R. cinerascens and none of the South Ameri- 
can examples of R. nigra intercedens have the sex determined; but each is readily 
divisible into two series according to size, in ali probability representing males and 
females, respectively, the sexual difference in size being almost certainly as well- 
marked in these two forms as in R. nigra nigra. 
4 Notwithstanding the anomalous distribution outlined above, I am unable to dis- 
tinguish satisfactorily specimens from the Pacific coast of Mexico and Central America 
{none have been examined, however, from the coast of Oaxaca) from true R. 7. 
intercedens. Most certainly they are not R. n. nigra nor R. cinerascens, Possibly a com- 
parison of larger series from both the Atlantic coast of southern Brazil, etc., and Pacific 
coast of Mexico and Central America may show differences sufficient to warrant the 
subspecific separation of the latter. 
