1900.] SHUFELDT—OSTEOLOGY OF THE STRIGES. 691 
increases to the last. The epipleurals of the leading ribs are the 
widest and generally the longest. The one on the second rib ina 
skeleton of this bird now before me is as wide as the rib at the 
point from where it starts; the one on the last rib being always the 
smallest. 
Clubbed at their superior extremities, each one overlaps the 
rib behind it, and in this manner adds stability to the thoracic pa- 
rietes, which is undoubtedly the function these little scale-like 
bones were intended to fulfill. The sternal ribs connect the vertebral 
ribs with the sternum. There are six of them, one articulating with 
each vertebral rib, and having a concave facet to receive it, while 
the last meets the sacral rib above and articulates with the posterior 
border of the fifth below. The first one is the shortest and most 
slender of all; the fifth is the longest. With the exception of the 
last, their superior ends are enlarged and compressed from side to 
side, while below their middles they become smaller; then turn- 
ing upon themselves, suddenly enlarge again, so as to be flattened 
from before backward, when each terminates by a transverse artic- 
ular facet for articulation with the sternum. Quite an interspace 
exists between their facets of articulation. They all make a gentle 
curve upward just before meeting their respective ribs. The sternal 
rib that articulates with the sacral rib is inserted in a long, shallow 
groove on the posterior border of the sternal rib that articulates 
with the last dorsal one, but does not meet the sternum, simply ter- 
minating in a fine point on the posterior border of the sternal rib 
mentioned. From before backward the sternal ribs make a grad- 
ually decreasing obtuse angle with the vertebral ribs, while the 
angle they make with the sternum is a gradually increasing acute 
from the fifth to the first. On the anterior surfaces of their ex- 
panded sternal ends are to be found on each a minute pneumatic 
foramen or two. ‘The anterior third of the lateral borders of the 
sternum is the space allotted for the insertion of these bones. 
The Burrowing Owl being a bird not possessed of any consider- 
able power of flight, or the necessity of having that flight ever long 
sustained, a circumstance arising from the life it has come to lead, 
we would naturally expect to find, in the course of a study of its 
anatomy, those characteristic modifications of the various systems 
which pertain to species of the class in which that gift has always 
been. a secondary consideration. Nor are we disappointed in this 
expectation, for a glance at the size of the sternum of this Owl, 
