272 REVIEW OF AMERICAN BIRDS. [PART I. 
lower mandible falling within its chord. Nostrils superior, broadly open, and 
nearly circular, without any adjacent membrane, the edges rounded. Legs 
stout. Tarsus equal to middle toe without claw; the joint feathered ; lateral 
toes about equal; the basal joint of the middle toe half free internally, rather 
less so externally. Claws strong, much curved 
The preceding diagnosis is intended to characterize two groups 
of Swallows, differing especially from all others in their thickened 
form, robustness of bill and feet, and especially in the elongated, 
comparatively powerful bill, the upper jaw degurved, its commissural 
edge much sinuated from the base, instead of as in all the others— 
being nearly straight to near the tip—so that a line from angle of 
mouth to tip will include the whole lower jaw. With these characters 
in common, there are two well-marked subgenera, recognizable as 
follows :— 
Procyre. Plumage glossy black above. Tail deeply forked, the lateral feathers 
much and gradually pointed. Bill most robust; upper outline convex 
from base. Tarsus with a few feathers only at base, on inner face. 
Puzorrocne. Plumage dull mouse brown above. Tail emarginate, or but 
slightly forked ; the lateral feathers very abruptly pointed, and rounded. 
Bill weaker and more depressed ; upper outline straight to near the tip. 
Tarsus with a line of feathers along inner edge for two-thirds the length 
from base. . 
a. PROGNE, Boie. 
Bill notched, robust, and deep ; the commissure much sinuated, convex, and 
ascending to the nostrils, then concave to the tip. Maxilla convex above from 
base; lower mandible slightly convex below, much more so above. Frontal 
feathers with a few bristles at base; none appreciable in chin. The upper 
joint of tarsus covered with feathers slightly adherent along inner face above, 
but not extending along the groove. Scutelle distinct. Lateral toes about 
equal, reaching to base of middle claw; all the claws very strong, and much 
curved. Tail much forked; the feathers much pointed; the wings pointed, 
reaching beyond tip of tail. Plumage compact; glossy black above, with 
purple, violet, or blue reflection. Below either similarly colored, or with 
white belly and crissum. ; 
I have found it very difficult to come to any definite conclusion in 
reference to the species of Progne inhabiting the continent of Ame- 
rica, or to determine with accuracy their geographical distribution, 
notwithstanding the large number of specimens examined, including 
those in the Phila. Acad. of Nat. Sciences. This is due, in great 
measure, to the variation of plumage with age and sex—the young 
birds of one species representing the adult plumage of another—and 
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