OSTEOLOGY OF BIRDS 



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just within the costal borders and the anterior border of the body ; 

 and at the bases of triangular pits, one of each, which occupy the 

 inner aspects of the costal processes. 



The hinder border of the sternal body is gently concave, and in 

 the specimen in hand the right side is pierced by two foramina, 

 while only one occurs on the left, as shown in figure 26. In many 

 specimens there is but one foramen upon either side, and occasion- 

 ally one or both of these may be very small indeed. A specimen in 

 the collections of the United States National Museum (no. 9383) 

 marked Circus jardini shows the sternum to be entire save 

 a pin hole foramen on the right side. It is also peculiar in having 



Fig. 26 



Fig. 26 The sternum of Circus, viewed from below. I have specimens before me 

 wherein the sternal foramina are exceedingly small, and I should not be at all surprised 

 to find a sternum of this hawk lacking these foramina entirely. 



Fig. 27 Heads of scapula, clavicle and coracoid, inner aspect, showing their mutual 

 relations, s, scapula; cl, clavicle; and c, coracoid. Same specimen as figures 19-22, 

 24-26. Life size from nature. 



the carinal angle dilated, and pneumatic fossae on the inner aspects 

 of the costal processes. The sternum of Falco sparverius 

 has a large elliptical foramen on either side, whose peripheries so 

 far encroach upon the posterior margin of the sternal bod)- as to 

 slightly absorb it at the point of tangency. In Falco r.colum- 

 b a r i u s these foramina are well within this border. 



But one pair of muscular lines presents itself upon the otherwise 

 smooth ventral surface of the sternum of Circus. Two of the lines 

 are seen on each side of the keel [rig. 26]. The carinal angle is 

 rounded, the anterior border of the keel being concave, while the 



