fiV. 



rETROCIIELIDON. 



2S7 





hoses cf the inner and niijldle toes. The lateral toes are nearly 

 t'(|iial, the outer, if anything, slightly longer; the entire basal joint 

 of the outer adherent to niiddle | the membrane just referred to ex- 

 tomliiig along the basal joint of the inner. The basal joint of the 

 middle is free cxterinilly at extreme end. The feathers of crissum are 

 very full, and reaeh nearly to end of tail. 



This is one of the most natural genera of American Swallows, cm- 

 hracing a con.siderable number of speeies, all characterized by the 

 rufous rump. H. nigj'icaus, Vieill. {Collocalia arbon-a oi Gould), 

 from Australia, appears to be strictly congeneric, as first suggested 

 by Cttbanis. The development of bristles in the chin and among 

 the frontal feathers npi.>.ars quite characteristic, giving a roughness 

 to the forehead very different from the softness and smoothness of 

 Attk'ora and other genera. 



The diagnostic characters of the principal American species of 

 Petrochclidon are as follows: — ; • J ; ' 



Common Chauactkrs. — Above steel blue ; the feathers of the Inter- * 



scapulnm with concealed wlivtish edgeH; no whitish median 

 or basal down. Rump and narrow nuchal band chestnut; 

 crii<siin» gray hrowu, tinged anteriorly at least with chestnut ; 

 the longer feathers and inner side of lateral tail feathers edged 

 with wiiitish. Middle region of belly white. Usually with 

 a wiiilish or reddish frontal band. ' • 



Chin and throat, ti'ith side of head, and continuous with 

 nuuhal band, chestnut brown. 



Jugulum with large blue-black pnich. Chestnut of 

 throat darker than that of rump. 



Frontlet reddish-white, with narrow band of 



black along upper mandible . . . lunifrons. , 

 , Frontlet chestnut brown, without black at 



base of upper man(iible . . . swainsoni. , 



Jugulum plain, witliout black spot. Chestnut of 

 throat lighter than that of rump. Frontlet 

 chestnut brown. •.'.'. 



Sides of body only slightly tinged with chest- 



"at fulva 



' : Sides deep chestnut, continuous with that of 



breast and crissum. Size smaller . paciloma. 



Chin, throat, and sides of head white. i 



Fore part of breast chestnut, without black spot. 

 Sides faintly tinged with same. 



Frontal band obsolete ri^ficolhris. 



P. nigricans, of Australia, lacks the nuchal band ; the sides of 





