320 SYSTEMATIC SYNOPSIS. — PASSERES — OSCINES. 
is scarcely or not half as long as the Ist; secondaries and their coverts also very short; all 
these quill-feathers broad and stout. An acute, thin-bladed and somewhat faleate wing, of 
surpassing volatorial power, results from these modifications. Tail of 12 rectrices, perhaps 
abnormally only 10, usually forked, or at least emarginate, and often deeply forficate, the 
outermost feathers being in this latter case narrowly linear in shape for a considerable dis- 
tance. Feet short, small, 
and weak, ill-adapted to 
secure foot-hold, and very 
badly formed for walk- 
ing. Swallows scarcely 
use their feet for locomo- 
tion, relying mainly upon 
their prowess of pinion. 
The tarsal envelope thor- 
oughly Oscine in struct- 
ure, being scutellate in 
front and laminate behind; 
it is sometimes partially, 
or almost entirely, feath- 
ered; the tarsi are com- 
monly shorter than the 
lateral toes. The digits 
possess the normal number 
.of phalanges; the basal 
phalanx of the middle 
digit is commonly coherent 
with one or both lateral 
toes; the hallux is ordi- 
nary, and not reversible. 
The digits are commonly 
naked and seutellate, rare- 
ly feathered to the claws. 
The claws are compara- 
tively stroug, compressed, 
well-curved, and acute, 
apt for clinging. The 
plumage is soft, smooth, 
and blended, most fre- 
quently glossy or even 
iridescent, but sometimes 
vO i i lustreless. Head ek 
DN, DONA at broad, and depressed ; 
Zea VTL Bil neck short. Mouth capa- 
Fic. 180.— Upper, European House Martin, Chelidon urbica; lower, Bank cious, its greatest width 
Swallow, Cotile riparia. (From Dixon.) equalling that of the head. 
This is a perfectly natural group, well distinguished by the foregoing characters. The 
swallows alone represent, among Oscines, the fissirostral type of structure; they have a close 
superficial resemblance to the swifts and goat-suckers of another order, but the relation is one 
of analogy, not of affinity, though all these birds were formerly classed together in the highly 
unnatural ‘ order” Fissirostres. (Sec beyond, under Cypselide aud Caprimulgide.) 
= rr 
‘i 
