OSTEOLOGY OF BIRDS 6l 



The inner condyle of tlie quadrate is lower than the outer, and at 

 the same time the smaller of the two. 



Parker tells us that " in the Sparrow hawk distinct pterotic and 

 sphenotic centers are developed ; and the orbitosphenoids are pre- 

 ceded by cartilai^e." [Morphology of the Skull, p. 264] 



Axial skeleton [tig. 25]. The cup for the occipital condyle on 

 the anterior aspect of the atlas of Circus presents a distinct notch in 

 its superior periphery. Aljove it, the neural canal is a transverse 

 ellipse, the neural arch closing it superiorly being quite broad. 

 Below, two short processes are directed backward behind the part 

 bearing the articular cup. 



The " odontoid process " of the a.ris is compressed from above 

 downward, its surface being flat superiorly, convex below. The 

 neural canal is circular, and the arch above supports three stumpy 

 processes, the lateral diapophyses and the neural spine. Beneath 

 the odontoid process the atlantal articular surface is a shallow con- 

 cave ellipse, placed transversely. Behind this, the body of the bone 

 is compressed from side to side, wdth longitudinal median crest, 

 terminating posteriorly in a knoblike process. 



The ^d vertebra presents pre- and postzygapophyses ; the articular 

 facets on the first being directed upward, those behind directed 

 downward. These processes in this vertebra are united by a hori- 

 zontal plate of bone, which lends to this segment a very solid ap- 

 pearance not possessed by those behind it. It is pierced about the 

 middle on either side, near the outer margin, by a minute 'foramen. 

 A median neural spine projects backward from the posterior border. 



The neural canal is cylindrical, and the arch slightly overhangs it 

 behind, but recedes from it anteriorly. On either side of the verte- 

 bral canal is present a minute perforation ; the parapophyses having 

 short spiculae directed backward. A median, oblong hypapophysis 

 is situated posteriorly, directly above which is the articular facet for 

 the fourth vertebra. It is concave from above downward, and 

 convex from side to side, ithe reverse being the case in the anterior 

 facet, which is directed downward and slightly forward. 



In the 4th vertebra the pre- and postzygapophyses are connected 

 by a delicate spine ; the articular surfaces on the former are slightly 

 inclined toward the median plane and each other, the reverse being 

 the case on the latter. The neural spine is more stumpy and has 

 worked toward the middle of the arch ; the canal is smaller and still 

 circular; while the vertebral canals are larger, longer, and their 



