PROGNE. 981 
the back; chin, throat, jugulum, and sides of head (below the centre of teh 
eye) neck and body, with inside of wings, grayish-brown, without gloss or 
lustre (as in Cotyle riparia), rather lighter along the median line. Rest of 
under parts dull white, not very sharply defined, passing behind into pure 
white on the anal region and crissum—the latter having the shafts of the 
longer feathers dusky, in contrast with the snowy white of the plume. A , 
concealed white stripe on the sides under the wings, as in other Progne. Tibia 
gray, the feathers tipped with whitish. 
The female (30,717) is quite similar, with much less gloss above, the white 
of the belly apparently passing further forward, and still less sharply defined ; 
the throat a little lighter. 
(No. 30,718, %, Guatemala.) Total length, 6.30; wing, 5.10; tail, 2.70; 
perpendicular depth of fork, .55; difference between Ist and 9th primary, 
2.55; length of bill from forehead, .50, from nostril, .28, along gape, .84; 
width of gape, .62; tarsus, .49; middle toe and claw, .73; claw alone, .23; 
hind toe and claw, .46; claw alone, .22. 
This Mexican and Central American species has generally been 
considered to be identical with the West Indian P. dominicensis, 
but a comparison of large series of specimens shows considerable _ 
differences. It is decidedly smaller, and the depth of fork of tail 
only two-thirds as great. As to color, none of the specimens before 
me exhibit any trace, on the under surface of the body, of the 
glossy steel blue of the back, found in males of dominicensis ; in 
this respect resembling females and immature males of the latter 
species. From these, however, it may be distinguished by smaller 
size—even in the males—and by having the shafts of the longer 
crissal feathers dusky, instead of being pure white. The white of 
the belly is less abruptly defined against the gray of the breast 
(which is darker also), and apparently occupies a wider space. 
The male bird (No. 30,718), the measurements of which I have 
given, appears to have a disproportionately short foot. In No. 
30,717, supposed female, from Duefias, the dimensions of the leg are 
as follows: Tarsus, .56; middle toe and claw, .81; claw alone, .27; 
hind toe and claw, .51; claw alone, .26, or nearly the size of P. 
subis with longer middle toe and claw. Other specimens are inter- 
mediate somewhat in this respect. It may be that the differences 
indicate a second species, but I cannot define it from the materials 
at my command. ‘The only other difference I note is a greener or 
less purple gloss to the back. 
It is barely possible that fully adult males of this species may 
have steel blue throats, as in true dominicensis, although I find no 
allusion to the fact in any description. Even in this case, however, 
the smaller size, less deeply forked tail, and dusky shafts of the longer 
crissal feathers will distinguish them. 
