358 
I>R. It. W. SHUFELDT S MORPHOLOGICAL 
On the Trachea , Visceral Anatomy , and other parts. 
More for my own satisfaction than with the expectation of 
revealing any structure that would prove to be different from 
what we already know of the morphology of the trachea or other 
parts in the Passerine birds, I examined the wind-pipe, its mus- 
cular and associate parts, as I did the several organs in the 
chest and abdomen of these American Swallows, but found 
nothing that required to be specially noted here. 
The trachea exists as we find it in most true Passeres, as do 
the several pairs of muscles at its lower larynx. I found the 
“ sterno-tracheales ” to be very delicately formed indeed, almost 
of hair-like proportions in some of the genera, as in Progne. 
The gall-bladder is of good size, and the right lobe of the liver 
the larger division of that organ. 
Cseca coli are present in Sw allows, but are of almost rudi- 
mentary proportions, and in some cases might be easily over- 
looked. 
It is my intention to refer to a few of these points again, when 
we come to consider the visceral anatomy of the Swifts and 
Humming-birds. 
The Osteology of the Hirundinidce. 
Skeletons of representatives of all the Hirundinidce of the 
United States are before me, and in sufficient number, so that 
a general definition for this part of the structure of these birds 
becomes quite possible, and will be given here. It is my inten- 
tion, however, to be brief in this matter, not only on account of 
space, but in view of the information already given. 
Of the STcull . — When I came to compare and examine the 
skulls of our seven species of Swallows, I was surprised to find 
them presenting such striking differences in their general form. 
Not but that they could each and every one of them be recog- 
nized at once as skulls of Swallows, but rather that they possess 
characters quite distinct and peculiar to the species, and there 
would be no difficulty whatever in telling, for instance, the skull 
of a Barn-Swallow from one of a Cliff-Swallow — so diverse is the 
general outline of each. 
In Progne subis (PI. XXI. figs. 18, 19, and 20) we find a skull 
