STUDIES OF THE MACRO CHIDES. 
363 
perhaps rudimentary, vertebra at the eucl of the series of the 
caudal segments. 
Further, I find the arrangement of the free vertebral ribs and 
their uncinate processes the same for all Hirundinidse, as I found 
them to exist in the Violet-green Swallow in my former memoir. 
This arrangement consists in. their having 12 cervical vertebrae 
that do not possess free ribs ; the thirteenth has a rudimentary 
pair ; the fourteenth has them better developed, and even may 
have uncinate processes upon them ; the fifteenth are the first to 
connect by costal ribs with the sternum, as do the ribs from the 
sixteenth to the nineteenth vertebrae inclusive. The twentieth 
is the first vertebra appropriated by the pelvis, and this latter 
compound bone monopolizes ten of these segments, so that the 
first free caudal is the thirtieth vertebra of the spinal column. 
Thus far at least one Swift {Micropus) was found by me to 
exhibit an arrangement similar to this, and later on we may look 
into the matter for Chcetura. 
The Humming-birds possess, as I have elsewhere stated, but 
32 vertebrae and a pygostyle in their spinal column. 
Every species of our Swmllows possesses a pelvis of a pattern 
characteristically its own, so that had we before us a dozen pelves 
of Progne , a dozen of Clielidon, and a dozen of each of the others 
we should have no difficulty, after once becoming acquainted 
with them, in picking out the several varieties correctly. Then, 
again, these pelves all strictly fall within the general description 
applied to what we please to call a Passerine pelvis , so far as our 
present knowledge and ideas of such a bone can be formulated. 
Now there is nothing that I can at this moment place my finger 
upon iu the pelvis of a Swift that debars it from being classed in 
the same category ; and indeed, when we come to examine into 
the matter closely, the differences between the pelves of Micropus 
and Progne are no greater than are the differences between the 
pelves of Progne and Clielidon. 
Ornithologists have long ago placed on record descriptions of 
the shoulder-girdle and sternum of Hirundiue birds, and the 
morphology of these parts in them is so well-known that to say, 
that although each species of Swallow has a characteristic form of 
sternum and shoulder-girdle of its own, these elements of the 
skeleton in all of them are strictly Passerine, — will sufficiently 
meet our aims in the present connection. 
In my memoir iu the P. Z. S. already referred to I made com- 
LINN. JOURN. — ZOOLOGY, VOL. XX. 28 
