A^o.4.] SHUFELDT ON THE OSTEOLOGY OF SrEOTYTO. 101 



remainder of its skeleton with regard to areas for muscular attacbments, 

 reveals to us the disproportion of the surface supplied by that bone for 

 the attachment of the pectorals. That its dimensions are relatively 

 contracted is proved by actual, comparative, and proportional measure- 

 ments of the bones with other species of its family, individuals of which, 

 at the best, are not noted for their i:)owers of flight as a rule, and con- 

 sequently the htiemal spine does not present so i>rominent a feature of 

 the skeleton as it does in other species of the Class Aves where vigor- 

 ous flight is habitual. Life-size figures of this bone, viewed from the 

 three principal i)Ositions for the purpose of study and measurement, are 

 ofiered to the reader in PI. I and PL II, Figs 5 and G. The concave 

 dorsal aspect of the body is smooth, being traversed iu the median line 

 by a very shallow groove that lies immediately over the base of the 

 keel. This groove terminates, within five millimeters of the anterior 

 border, in a little depression, at the bottom of which are discovered 

 I)neumatic 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 supi)lied in this respect as it is in some other 

 Owls. The costal borders supporting the transverse articular facets for 

 articulation with the hsemapoj^hyses 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 

 l)neumatic foramina. The anterior border is smooth and rounded, with 

 a median shallow concavity occupying its middle third. At its extrem- 

 ities, laterally, the costal processes arise with a general forward tendency 

 at first, but with their superior moities directed backwards. The costal 

 borders terminate at the posterior borders of these 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 i)rincipally in the horizontal plane. They melt away into the 

 liody 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 ui^wards, disappears gradually 

 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, occui)ying its usual position in the 

 middle line, is comx)aratively 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- 



