STUDIES OE THE MACROCHIRES. 
353 
very closely to some Cuculince, namely the Cypseli. For this 
reason I usually place it at the end of the Passerinae, in the 
vicinity of the anomalous cuculine form just mentioned, which 
stands in the same relation to the true Cuckoos as the Swallows 
to the ordinary Song-birds. However, pterylographically, 1 Ti- 
rundo does not differ from the rest, but rather harmonizes com- 
pletely with Dicceum , in that the rows of single contour-feathers 
uniting the saddle with the rump-band are either entirely deficient 
(II. rustica , S. urbica ) or indicated only by two rows of very sparse 
contour-feathers ( S . rupestris ). The dilatation of the pectoral 
part of the inferior tract is somewhat divergent at the end. The 
number of remiges is eighteen, of which nine are on the hand, 
and of these the first is the longest ; the first six secondaries are 
remarkable on account of their broad, emarginate extremities ” 
(pp. 84, 85, 4 Pterylography ’). 
Now, in Progne I note that the “ saddle ” at the end of the 
spinal tract is very broad, although forked as in Sir undo urbica , 
but the posterior extremities of the limbs of this bifurcation are 
joined, on either side, to the anterior end of the rump-tract by 
distinct and well-marked rows of contour-feathers. Further, the 
bifurcation of the “ saddle ” takes place at about the middle of 
the back, and not nearly so low down, namely between the thighs, 
as in Sirundo. Another point to note upon this dorsal aspect 
in Progne is that the “alar tracts” are very extensively joined 
with the anterior endings of the “humeral tracts.” In Sirundo 
Nitzsch even seems to leave an unfeathered space, on either side, 
in these localities. The “ capital area ” is the same, but in 
Progne there are no naked areas around the eye and auricular 
orifice, as in Cgpselus, and as Nitzsch has also drawn them for 
H. urbica. 
Under the throat in Progne and in most Swallows we find a 
longitudinal naked strip running down close to and just within 
the ramus of the mandible, on either side, which terminates at 
about the angle of the jaw. It will be remembered that in the 
Whip-poor-wills and others this feature is also present, except 
in them it assumes a somewhat different type, the feathers of the 
throat being arranged in regular rows. I am inclined to believe 
that there is a reason for this, which is, that in these birds, accus- 
tomed as they are sometimes to swallow very large insects, an 
operation which must distend the throat, or even momentarily 
