328 FIELD MUSEUM OF NATURAL HISTORY ORNITHOLOGY, VOL. I. 



barred with black and white; outer web of second (outer) primary with 

 only a slight indication of a white spot on the exposed portion near the 

 base, the third the same, but the spot somewhat more exposed; length 

 of black band on the central rectrices 23 mm. 



Wing, 169; tail, 120; tarsus, 31 mm. 



Female: Wing, 182; tail, 126 mm. 



Specimens examined: British Guiana Essequibo River, id", i 9. 



Comparative differences: Compared with other races having deeply 

 colored unspotted under parts, C. s. perplexa differs from andina and 

 intermedia in its much smaller size; absence of pronounced white spots 

 on the outer webs of the second and third (outer) primaries, etc., etc. 

 From ochracea it differs in its smaller size, shorter tail band, etc. It 

 somewhat resembles C. s. margaritensis, but the under parts are more 

 deeply colored; the upper parts more rufous chestnut; and it lacks the 

 well marked white spots on the outer webs of the second and third 

 (outer) primaries. From C. s. isabellina it may be distinguished at a 

 glance by its deeply colored under parts. 



Remarks: This strongly colored race probably ranges so far east as 

 Cayenne, as it agrees very well with Buffon's colored plate, illustrat- 

 ing the Emerillon de Cayenne (/. c.). Bonyan* also refers to the 

 Cayenne bird as the "Chestnut-bellied Falcon." That the deeply 

 colored under parts in this bird is not due to age may be assumed from 

 the fact that fully adult males of C. s. distincta (which approaches very 

 closely in coloration of the under parts to C. s. isabellina} have the under 

 parts very nearly as pale as in immature specimens. 



Cerchneis sparveria isabellina (Swains.). 



Falco isabellina Swains., Anim. in Menag., I, 1837, p. 281. 



Type locality: Demerara, British Guiana. 



Range: British Guiana (limits of range unknown) . 



Characters: Under parts unspotted or .with a few spots on the flanks 

 concealed by the wing; breast and upper abdomen washed with light 

 pinkish cinnamon or pale Isabella buff; lower abdomen, thighs, and 

 under tail coverts almost white; outer web of second (outer) primary 

 plain or with a faint trace of a small white spot; outer web of third 

 with two small white spots or a narrow white or whitish streak; inner 

 web of outer rectrix normally rufous] with one subterminal black band 

 and the tip white. 



*Proc. Zool. Soc. Lond., 1851, p. 60. 



t The specimen in the National Museum collection has the greater portion of 

 the inner web rufous, with two black bands near the end separated by a whitish 

 space. 



