102 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Tol.Yl. 



mg the posterior parts of the bone are sharp ; the lateral one, taken 

 from the ai)ices of the costal processes to their other and lower termi- 

 nations, are concave. As is the arrangement generally among Owls^ 

 the xii)hoidal 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 x^osteriorly 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 widths 

 The ventral and convex surface, like the dorsal, is smooth and presents 

 but two x>oints 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 back wards, 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 to the base of either costal process or outer an- 

 terior sternal angle. It is compressed, smooth, and thiu, but its stability 

 is greatly aided by the carinal ridge on either side, which commences, 

 strong and well marked at the base of the manubrium, just within the 

 anterior border running parallel with the latter, and disajipears as it ap- 

 proaches the carinal angle. The anterior border of the keel is sharp and 

 concave 5 the inferior border is convex, with the edge slightly thickened. 

 The point of intersection of these two borders anteriorly is rounded 

 and forms the carinal angle. The inferior border expands posteriorly, 

 and the keel terminating a short distance before arriving at the poste- 

 rior sternal border, the two become blended with the surface of the body 

 of the bone. 



Sacral vertebrcc; pelvis; and coccygeal vertehrce. — It is no uncommon 

 occurrence to find in the skeletons in many species of birds at least one 

 or more of the anterior sacral vertebrae articulating with a greater or 

 less amount of freedom with one another, but in the sacrum of the Owl 

 now under consideration, with the exception of a few faint lines indicat- 

 ing the original individuality of the vertebrae, the bones are thoroughly 

 anchylosed together and to the ossa innominata. From inspection of 

 this compound bone in immature birds, we find the usual number of 

 sacral vertebrae composing the sacrum to be thirteen. The anterior 

 face of the first possesses all the necessary elements for articulation with 

 the last dorsal. The neural spine has a thickened crest that soon meets- 

 the ilia on either side 5 its anterior edge is thin, and gives attachment below 

 to the interspinous ligament. The neural canal is circular, and the 

 prezygapophyses well marked. The articular facet of the centrur^ is iii 

 the vertical plane, with its curvatures similar to those ascribed to :he an- 

 terior facet on the centra of the dorsals. The neurapophyses are broad 



