SHUFELDT. ] OSTEOLOGY OF THE SPEOTYTO. 607 
three principal positions for the purpose of study and measurement, are 
offered to the reader in Pl. I and Pl. UW, Figs. 5 and 6. The concave 
dorsal aspect of the body is smooth, being traversed in the median line 
by a very shallow groove that lies immediately over the base of the 
keel. This groove terminates, within five millimetres of the anterior 
border, in a little depression, at the bottom of which are discovered 
pneumatic foramina, two or more in number, leading to the anterior 
thickened vertical ridge of the carina beneath. Other minute openings 
for the admission of air into the interior of this bone are seen among 
some shallow depressions just within the costal borders. The bone does 
not seem to be as well supplied in this respect as it is in some other 
Owls. The costal borders supporting the transverse articular facets for 
articulation with the hemapophyses occupy about one-third of the en- 
tire lateral border on either side anteriorly. At the bases of the major- 
ity of the depressions that occur between these facets are found other 
pneumatic foramina. The anterior border is smooth and rounded, with 
a median shallow concavity occupying its middle third. Atits extrem- 
ities, laterally, the costal processes arise with a general forward tendency 
at first, but with their superior moieties directed backwards. The costal 
borders terminate at the posterior borders of the processes, at a higher 
level than the anterior sternal margin does at their anterior borders. 
The coracoid grooves are just below the anterior border. They are 
deep, continuous with each other, having a greater depth behind the 
manubrium in the median line than observed at any other point. Their 
general surface is smooth and polished, looking upwards and forwards, 
and lying principally in the horizontal plane. They melt away into the 
body of the bone laterally, at points opposite and not far distant from 
the posterior articulations on the costal borders. The margin that 
bounds them below is sharp, travels at right angles from the median 
line at first to a point posterior to the costal processes, then making a 
little dip downwards, then again curving upwards, disappears gradu- 
ally with the groove it bounds. That portion of it from the point where 
it changes its direction to its termination is described by authors as the 
subcostal ridge. The manubrium, occupying its usual position in the 
middle line, is comparatively small, quadrate in form, compressed below, 
slightly notched and flattened above, its posterior surface forming the 
inner anterior surface of the coracoidal groove. All the borders bound- 
ing the posterior parts of the bone are sharp; the lateral one, taken 
from the apices of the costal processes to their other and lower termi- 
nations, are concave. As is the arrangement generally among Owls, 
the xiphoida] extremity of the sternum is four-notched, two on either 
side, the outer notches being the deeper. Both have rounded bases, and 
the processes that separate them are ample and possess rounded ex- 
tremities. The border upon which the keel ends posteriorly is square, 
though we have met with specimens in which it was slightly notched in 
the median line. The body is oblong, and, if we include the xiphoidal 
processes on either side, has a length half as long again as its width. 
The ventral and convex surface, like the dorsal, is smooth and presents 
but two points for examination. The pectoral ridge, faintly marked 
throughout its extent, originates on each side at a point near the outer 
borders of the coracoid grooves, running inwards and backwards, and 
dies away at the base of the keel near its middle. This little ridge 
denotes the line between the pectoralis major and minor. The keel is 
moderately well developed, the distance from the base of the manubrium 
to the carinal angle being equal to the distance from the same point at 
the base of the manubrium te the base of either costal process or outer 
