^2 XEW YORK STATE MUSEUM 



neck is thick and broad, being subelliptical upon section [fig. 25, 27] ; 

 while on the articular surface it extends to the glenoid cavity, and 

 is about half or a little more than that presented by the coracoid. 

 Upon its under 'surface, close to the line of articulation with this 

 latter bone, we find a circular pneumatic foramen, which is constant. 

 This line of articulation runs out to the end of the scapular process 

 of the coracoid, but beyond this the scapula is extended as a clavic- 

 ular process which meets the head of the furcula wuth greater or 

 less intimacy [fig. 27], thus closing in the tendinal canal. The 

 proper relations of these bones in Circus are shown in figure 27 of 

 the present treatise. In Circus all the thoracic pleurapophyses are 

 overlapped by the scapula, except the last two pairs, so we may . 

 judge from this that that bone is below the average length for birds, 

 not reacliing the anterior border of the pelvis. 



One would hardly expect from an examination of the sternal 

 bases of the coracoids that they decussated in their grooves, as these 

 parts are apparently exactly alike in either bone. The inner angle 

 is carried out as a sharp point while the outer is a stumpy process 

 [fig. 25]. A strong muscular line marks the shaft anteriorly, es- 

 pecially at its lower part, the shaft itself being stout and sub- 

 cylindrical at its middle third. Just below the inner end of the 

 scapular process, we find on the side of the shaft a long, shallow 

 notch, which in life is spanned by a delicate ligament, thus con- 

 verting the notch into a foramen. In some specimens this foramen 

 is completed in bone ; it may pierce the coracoid upon one side and 

 be a notch on the other. A specimen of Circus jardini 

 has it a shallow notch upon either coracoid [U. S. Nat. Mus. Collec. 

 no. 9383]. In many owls this foramen pierces the wing of the 

 scapular process of the bone near the center, as in Speotyto, where 

 I found it transmitted a branch of that cervical nerve coming from 

 between the 12th and 13th cervical vertebrae [see On the Osteology 

 of the Striges, Am. Phil. Soc. Proc. 1900, v. 39, no. 164, p. 700]. 



The scapular process of the coracoid has already been alluded to 

 above when describing the scapula. It is comparatively very small 

 and shows but little on direct inner view [fig. 2^]. It holds the 

 same position as seen in Ibycter americanus, ]\Iicras- 

 tur semitorquatus, Buteo borealis and others 

 studied by Ridgway, and so strikingly compared in his Outlines of 

 a Natural Arrangement of the Falconidae. 



Upon the anterior aspect of the coracoid or really on the head of 

 the bone, there is an elongated facet placed vertically and slightly 



