102 



BULLETIN 86, UNITED STATES NATIONAL MUSEUM. 



Breeding birds from Yucatan and Campeche represent the extreme 

 differentiation of this subspecies. Those from southern Chiapas, 

 from Guatemala, and southern Oaxaca, Mexico, are intermediate in 

 size between Chordeiles acutipennis micromeris and Chordeiles acuti- 

 pennis texensis, though in other respects like the former. A single 

 female from Atemajac, Jalisco, near Guadalajara (No. 281892, 

 U.S.N.M.), looks just the same as these intermediate birds from 

 Oaxaca and Chiapas, and is the basis for extending the range of the 

 present subspecies to Jalisco. This is probably correct, though the 

 possibility, of course, exists that this individual is not representative 

 of the birds breeding in Jalisco. Comparative average measurements 

 of specimens from different localities are as below : 



In this Yucatan race there exist the same four adult plumage 

 phases as in Chordeiles acutipennis acutipennis. 



Specimens examined. — Of this race 25 examples have been 

 handled, from the subjoined localities: 



Can^peche. — Campeche (June 8, 1900). 



Chiapas.— Tvixildi, Gutierrez (May 26, 1904) ; San Bartolome (Mar. 

 24, 1904) . 



Jalisco. — ^Atemajac (north of Guadalajara) (May 28, 1892). 



Oaxaca. — San Mateo (Aug. 5, 1869). 



Yucatan. — Rio Lagartos (Apr. 10, 14, 18, and 20, 1893), Mujeres 

 Island (Mar. 24, 1901) ; Merida (June 19, 1865) ; Chichen Itza 

 (Apr. 2, 1904) ; Izamal (June, 1905) ; Xbac (April, 1910). 



Costa Rica.— San Jose (Sept. 10, 1883; Oct. 29, 1891); Pigres 

 (Mar. 4 and 11, 1905). 



Guatemala. — Lake Atitlan (Apr. 8, 1906). 



Honduras.— Tvvi:s.i\\o (Sept. 30, 1887). 



Nicaragua. — San Geronimo, Chinandega (Mar. 25, 1904). 



Panama. — Gatun, Canal Zone (Jan. 11,. 1911). 



